Re: [time-nuts] GPS coordinate differences between APRS.FI and Google Maps
Perhaps aprs.fi is reporting in dd.mm (degrees.minutes) format vs decimal degrees. That would be consistent with the numbers you are setting. On Fri, Apr 20, 2018, 8:01 PM Azelio Boriani wrote: > aprs.fi uses google maps... have you taken a look to your raw packets? > > On Sat, Apr 21, 2018 at 12:34 AM, Scott McGrath > wrote: > > DATUM perhaps? > > > > Content by Scott > > Typos by Siri > > > > On Apr 20, 2018, at 5:20 PM, Russ Ramirez > wrote: > > > > This has probably been mentioned before, but there is a significant > > discrepancy between APRS.FI locations for DMR hotspots for example, and > > what my Trimble receiver and Google Maps says when I use my address to > > lookup the coordinates. > > > > On APRS.FI my location has to be 45.15 N, -93.39 W for the icon to be in > > the right location on the map. > > > > On regular Google Maps, my QTH is correct and matches what my Trimble > says > > via Lady Heather within a few seconds. 45.2586 N, -93.6554 W. > > > > Do any of you know what causes this, and did I do anything wrong > possibly? > > TIA > > > > Russ > > K0WFS > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4046 replacement
While we are on the subject of the 74HC4046, I would like to point out a confusing error in the TI datasheet for this part, found at http://www.ti.com/lit/ds/symlink/cd74hc4046a.pdf The waveform diagram for Phase Comparator 3, Fig. 7 on p. 5, has inverted waveforms for PC3out and VCOin. PC3out should rise at the leading edge of SIGin and fall at the leading edge of COMPin. The corresponding diagram in the NXP/Phillips datasheet, Fig. 11, is correct. On Wed, Apr 18, 2018 at 5:28 AM, Clint Jay wrote: > Why not try one, the 74HC4046 is pin compatible I think, you may need to > make some changes to use the '7046 version but you can then make a value > judgement if the flaw had in fact mainfested itself as a problem in your > design? > > --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Environmental sensor recommendations
I would like to put in a good word for the DS18B20 temperature sensor. It consumes very little power, uses the "1-Wire" protocol, and is available pre-wired in a variety of configurations, for example this https://www.adafruit.com/product/381 and this https://www.adafruit.com/product/642 resolution is 12 bits, .0625 C, range -55 to +125 C. You can connect a bunch of them in parallel on the same data pin if you want to measure temperature at different locations There is a pretty good 1-wire library for the Arduino. On Thu, Apr 5, 2018 at 7:19 PM, Mark Sims wrote: > Digital temperature sensors have some advantages (like nice factory > calibration), but also so issues. The IIC/SPI ones need to be mounted to > a PCB and also have quite a bit of thermal mass. They also need 4-6 wire > cables. They are hard to attach directly to a point that you want to > monitor. > > The advantage of thermistors is that they are small, cheap, readily > available with leads attached, and only require a two wire cable. You can > easily tape them to whatever point you want to monitor. > > The ADT7420 is $8 a pop + PCB + assembly + cable. Decent thermistors can > be had for less than a buck. > > -- > > > Check out ADT7420: > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWV or Net Clock controlled oscillator
Or if you want a bit more of a challenge, you might consider the DS3231 https://datasheets.maximintegrated.com/en/ds/DS3231.pdf This is a full-featured real time clock with a TCXO. It has a programmable 32KHz or 1 pps output. You can trim the frequency digitally via an I2C port in increments of about 0.1 ppm.It comes in a small package but you can get the Chronodot, a breakout version with 0.1" headers from Adafruit and elsewhere: https://www.adafruit.com/product/255 You can use the Chronodot by itself or hook it to an Arduino to access the full range of features. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] accurate 60 hz reference chips/ckts
On Thu, Dec 14, 2017 at 10:53 PM, Bob kb8tq wrote: > > > Of course this *assumes* an electronic approach. Given that it’s moving > pretty slow and you > only are looking at fractions of a millisecond, one *could* do an electro > mechanical design …... > > Bob > > There is interesting background on power grid frequency/time adjustment procedures here https://en.wikipedia.org/wiki/Utility_frequency#Time_error_correction_(TEC) and here https://en.wikipedia.org/wiki/Electric_clock#Accuracy -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] accurate 60 hz reference chips/ckts
Since the power line has the desired long term stability but is poor on the short term, I wonder if a solution might be to use it as the reference for a "power line disciplined oscillator." You would want a filter time constant of several hours in the control loop to smooth out the variations in the 60 Hz. Or it might be easier to rip the guts out of the Radio Shack clock, just keeping the display, and drive the display with an Arduino and a DS3231 RTC chip as the reference. On Thu, Dec 14, 2017 at 4:05 PM, Hal Murray wrote: > > apollo...@gmail.com said: > > Want to provide an accurate (relatively accurate) 60 hz reference to the > > chip. Some room inside for custom modifications. Does a TCXO or > similar > > exist in a small package that provides 60 hz ticks? > > I doubt if you will find a TCXO that puts out 60 Hz. But it's only one > chip > to make a divider. The trick is to do it in software rather than hardware. > > The real question is what sort of error pattern are you interested in. The > power company has good long term stability. How good is your TCXO? It > would > be fun to play with the numbers. On the other hand, can you derive your 60 > Hz from a GPSDO? > > -- > These are my opinions. I hate spam. > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why discipline Rubidium oscillator?
On Mon, Nov 20, 2017 at 7:14 PM, Jerry Hancock wrote: > Have to do a cost/benefit analysis for the wife... I hope she is not the type of person who sets her watch 5 minutes ahead so she will arrive on time! -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Discussion of precise time and frequency measurement
On Mon, Nov 13, 2017 at 12:32 PM, Gregory Beat wrote: > As a second’s error in time will be about a nautical mile in US > latitudes, I wonder if anyone has measured with GPS, how good the original > surveys were? > > Sent from iPad Air > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > I think one nautical mile per second is a bit off: 86,400 sec/day Earth's circumference at lat. 41 is about 16,200 nautical miles, so it's about 16200/86400 or 0.187 mi/sec There is an interesting book "Longitude by Wire" by Richard Stachurski that describes efforts in the mid 19th century to improve the accuracy of surveys and determine the precise position of North America relative to Europe. This culminated in the use of pulses on telegraph lines to transfer observatory time to remote stations. With this technique, very careful measurements, and mathematical advances they were able reduce the longitude uncertainty to less than 10 feet. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source
On Thu, Nov 2, 2017 at 9:04 AM, Chris Caudle wrote: > > > That sounds like you just designed the worst GPSDO ever. > > -- > Chris Caudle > > Yes but the price and power consumption are right. I guess it all depends on your application... -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source
On Wed, Nov 1, 2017 at 7:21 PM, MLewis wrote: > > And the DS3231 has: > - a 32K output, and > - an Active-Low-Interrupt/SQW output that can be set to PPS. > It's unclear to me how to sync the DS3231 PPS to the GPS PPS, or if that > can be done. > > > The DS3231 has an 8 bit register that will change its frequency in increments of about 0.1ppm. Thus you could discipline it to get its pps aligned with your reference. With an adjustment range of +/- 127, that's a maximum offset of 12.7 ppm. In the worst case you would have to move its pps 0.5 sec, which by my calculation would take about 41.667 seconds or about 11.5 hours. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OCXO Vectron 218Y44442
Sorry, this image http://www.patoka.ca/Vectron-218Y2/IMG_20171015_193511542.jpg On Mon, Oct 16, 2017 at 6:22 PM, Jim Harman wrote: > In your image ...125 it looks like there is a cold solder joint near the > bottom right, in the second "column" of pads, 3 pads up from the bottom. > > On Mon, Oct 16, 2017 at 4:10 PM, Vlad wrote: > >> >> Hello, >> >> I am wandering if anybody observe the behavior for OCXO, when its stop to >> reproduce the signal, and the only way to return it back to business is >> little mechanical stress. >> >> I have TWO of such OCXO. One of them is Austron 11.2 Mhz. And another one >> is Vectron model 218Y4442 9.8304Mhz >> >> In case with Vectron, I even disassemble it (to whom who brave here is a >> pictures): >> >> http://www.patoka.ca/Vectron-218Y2/ >> >> Then as I connect it to the PS, I realize it start to reproduce the >> signal again ! Before this it was nothing ! I tried different PS before to >> open this "can" as a last resort. >> >> For the Austron - I didn't disassemble it. Instead I just kick it a >> little bit. And immediately after that, it start to produce the signal ! >> >> >> -- >> WBW, >> >> V.P. >> ___________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> > > > > -- > > --Jim Harman > > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OCXO Vectron 218Y44442
In your image ...125 it looks like there is a cold solder joint near the bottom right, in the second "column" of pads, 3 pads up from the bottom. On Mon, Oct 16, 2017 at 4:10 PM, Vlad wrote: > > Hello, > > I am wandering if anybody observe the behavior for OCXO, when its stop to > reproduce the signal, and the only way to return it back to business is > little mechanical stress. > > I have TWO of such OCXO. One of them is Austron 11.2 Mhz. And another one > is Vectron model 218Y4442 9.8304Mhz > > In case with Vectron, I even disassemble it (to whom who brave here is a > pictures): > > http://www.patoka.ca/Vectron-218Y2/ > > Then as I connect it to the PS, I realize it start to reproduce the signal > again ! Before this it was nothing ! I tried different PS before to open > this "can" as a last resort. > > For the Austron - I didn't disassemble it. Instead I just kick it a little > bit. And immediately after that, it start to produce the signal ! > > > -- > WBW, > > V.P. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Resoration of 5065A - continued...
On Mon, Sep 11, 2017 at 9:36 AM, paul swed wrote: > I would simply slap a 741 into position to see how it behaves. > Also check those zeners for +/- 14.7V. They go bad. > Regards > Paul > WB8TSL > > ... but leave the pins that the 709 uses for external frequency compensation (1, 5, and 8 on the can or mini-DIP) unconnected. The 741 has internal frequency comp and uses pins 1 and 5 for an optional offset null instead. --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] RS232 output on a 53181A
Well ASCII * is 2a in Hex, p is 70 so that seems an unlikely substitution for a failing EPROM. But 0 is 30 Hex, only one bit different from p. On Wed, Jul 12, 2017 at 10:39 AM, Angus wrote: > Hi, > > I've just been using an Agilent 53181A, but the serial output is not > quite what I had expected. On the 53131A's that I've used the > placeholder character on the RS232 output is an asterisk, but with > this unit it is a lower case 'p'. Where the 53131A sends '2,*** u', > this 53181A send '2,ppp u'. The only references to a placeholder that > I saw in the manuals referred to an asterisk. > > The firmware version is 4613. > > Anyway, just wondering if anyone knows if this is correct, or maybe > it's just the EPROM starting to fail. > > Thanks, > Angus. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] BTTF : Austron 1210-C Crystal Clock
Thanks for the references, Tom. The clock portion must have been a 113. Operation at 1 kHz would certainly explain the whine. I also remember taking a peek inside the oven and seeing an impressively large chunk of quartz. On Mon, Jun 12, 2017 at 12:45 AM, Tom Van Baak wrote: > Hi Jim, > > Maybe a version of this?: > > http://leapsecond.com/history/Benchmark.htm > > The audible (1 kc) whine was probably from the model 113 or 115. See if > any of the following pages remind you: > > http://leapsecond.com/hpclocks/ > http://www.radiomuseum.org/r/hewlett_pa_frequency_divider_and_cl.html > http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1959-11.pdf > http://hpmemoryproject.org/wb_pages/wall_b_page_01.htm > http://hpmemoryproject.org/news/2012/vintage_01.htm > > /tvb > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] BTTF : Austron 1210-C Crystal Clock
On Sun, Jun 11, 2017 at 9:01 PM, paul swed wrote: > But perhaps whats magical gold is the Patek Phillipe clock movement. Just a > guess.I hear they are quite annoying clunkers actually. I have never owned > one but a fellow in Europe was telling me you can really here them tick. > In my first job back in 1973 I inherited a lab that included what must have been an HP 100C frequency reference. It took up most of a rack and divided down a 100KHz oscillator with cascaded injection-locked 10:1 multivibrators that used metal octal-base tubes. The final frequency of 100 Hz drove a beautiful clock that made a very audible whine when it was working. This must have been an option because I don't see any reference to it in the 100C manual. At the bottom of the rack was a Hammarlund radio to tune in WWV for calibration. IIRC the clock motor also drove an adjustable cam and microswitch. The receiver's audio was fed through the switch. I think the idea was that you could accurately measure the oscillator drift by adjusting the phase of the cam until you could hear WWV's tick during the short time the switch was closed. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Poor man's oven
On Tue, Jun 6, 2017 at 10:00 AM, Riley, Ian C CTR NSWC Philadelphia, 515 < ian.riley@navy.mil> wrote: > Is there a practical minimum for what voltage you can feed into AREF? > It is hard to find on the data sheet, but the minimum voltage for an Arduino's AREF is the internal analog reference voltage - 1.1V for the Uno, 2.56V for the Leonardo or Micro. The 32U4 chip in the Leo and Micro has options for differential analog input and gains of 10, 40, or 200 but they are not supported by the Arduino IDE - you have to set the internal registers directly to use them. Also the input amplifier is pretty slow. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TruePosition and Arduino Progress
Sorry, I may have over-simplified. You sketch might look something like
this, assuming the PPS is connected to pin D2 and the rising edge makes the
second:
volatile boolean PPS_ReadFlag = false;
void setup () {
...
attachInterrupt(digitalPinToInterrupt(2), serviceRoutine, RISING);
...
}
void serviceRoutine() {
PPS_ReadFlag = true;
}
void loop () {
while (!PPS_ReadFlag) {
while(Serial.available()) {
--parse the next character and set a flag if the time is valid--
}
}
if(timeValid) {
-- update display or whatever --
PPS_ReadFlag = false;
}
}
On Sun, May 21, 2017 at 2:56 PM, Jim Harman wrote:
> Another way to do is to use the 1 PPS to trigger an interrupt on the
> Arduino. Look at the documentation for attachInterrupt(). In the interrupt
> routine, have it set a flag. The flag variable should be declared up front
> as volatile.
>
> Then in your main loop, do all your parsing then loop waiting for the flag
> to be set. When set, update the clock then clear the flag and repeat.
>
>
>
> On Sun, May 21, 2017 at 2:32 PM, Chris Albertson <
> albertson.ch...@gmail.com> wrote:
>
>> To add to my last message.
>>
>> You CAN collect all the data then parse it like you are doing if you
>> were to move to an interrupt driven serial port reader. Each
>> character is then read by the interrupt handler anyplace in a large
>> circular buffer. The parcer then reads out of the other and of this
>> buffer.
>>
>> The phlegm with the current code is the parse ingnores serial input
>> and will drop data, in also ignore the PPS and will as you found drop
>> pulses.
>>
>> Typically in real time processors like your that must be interrupt
>> driven or they must poll MANY times laster then the data arrives
>>
>> so as I wrote before, parsing the data stream one character at a tie
>> is in effect pooling the serial port much faster then characters
>> arrive.Adding a ring buffer and interrupts guarantees yo never
>> miss a character and certainly you need to interrupt in the PPS to
>> handle the case there three s serial data and the PPS at the same
>> time.
>>
>> The ring buffer is like you big string except you data data onto one
>> end at the same time as soured data off the other. Hopefully the ring
>> buffer never has much data in it as the parser should be fathers then
>> the serial line. BUT if a PPS happens then the parser in interrupted
>> while the display updates so th ring buffer might get filled up a
>> little. But the ISR terminals the parser clears the buffer.
>>
>> On Sun, May 21, 2017 at 11:20 AM, Chris Albertson
>> wrote:
>> > The problem is that you get the ENTIRE string then parse it. This is
>> > not going to work well as you found out. Your CPU spends almost the
>> > entire time waiting for characters to come in slowly off the serial
>> > line. You are just waiting on bits and wasting CPU cycles
>> >
>> > What you need to do is parse one character at a time. I bet your
>> > parser reads one character at a time from the string. Have it read
>> > one character at a time directly from the serial port. (Use a state
>> > machine. It will work for such a simple job as this)
>> >
>> > Yes if your CPU was MUCH faster your plan could work. But on some
>> > GPSes the data never has a break. You are trying to do ALL the work
>> > in the break but actually most of the down time when you should be
>> > working is between the characters.There is not a lot of work a
>> > finite state machine needs to do between characters, just move state
>> > based on a 'character class" table. I you ever studied this
>> > formally, what you are building here is a "lexer" not a parcer. The
>> > "Language" is not recursive and you never need to backtrack so it can
>> > be de-coded literally one character at a time.
>> >
>> > You DO really want the 1PPS to drive an interrupt. Thisway you just
>> > continue working on the data stream and don't wait for the PPS. When
>> > the PPS happens you do something QUICK. never do anything time
>> > consuming in the ISR or you will miss the next serial character.
>> > increment a seconds count and write two bytes the the LCD and exit
>> >
>> > On Sun, May 21, 2017 at 6:45 AM, Ben Hall wrote:
>> >> Good morning all,
>> >>
>> >> A quick update for those interested on my Arduino code development for
>> the
>> >> TruePosition boards. I've got Arduino code
Re: [time-nuts] TruePosition and Arduino Progress
age, it seems > like it > >> is still parsing when the 1PPS tick comes in...so it will display > seconds as > >> follows: 30, 31, 33, 34, 35, 36, 37, 39, etc... > >> > >> (If I don't wait for the 1PPS tick, it seems that my clock is one second > >> fast. I say "seems" to be fast, as the time agrees with an NTP clock > on one > >> computer, but seems a half second slow per GPSCon's time display on the > >> Z3801. I think I need to put up the antenna and check against WWV.) > >> > >> I've got one of those cheap little USB logic analyzers on order to > figure > >> out how much time elapses between the clock, extstatus, status, and 1PPS > >> tick. I may need something faster than an Arduino Uno to do this. > >> > >> I'm sure there is a way to do this with an interrupt...but I couldn't > make > >> that work yesterday. More to follow. > >> > >> thanks much and 73, > >> ben, kd5byb > >> ___ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >> and follow the instructions there. > > > > > > > > -- > > > > Chris Albertson > > Redondo Beach, California > > > > -- > > Chris Albertson > Redondo Beach, California > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS seconds conversion on an Arduino
On Sun, May 14, 2017 at 9:25 AM, Ben Hall wrote: > I think I can make the process work *if* the time library doesn't hold the > answer. (and I think it does) The Arduino Time library can convert back and forth between numeric year/month/day/hour/minute/second and a uint32 representing the number of seconds since 1/1/1970. It does not take leap seconds into account however so you would have to make an adjustment for them. It is reasonably well documented and includes some handy conversion macros and examples. As with other Arduino libraries, the source code is provided so you can see how they did it. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TruePosition on an Arduino
On Sat, May 13, 2017 at 3:15 PM, Ben Hall wrote: > I've been wanting to dive more into Arduino...so I figured I'd write my > own interface program. The last software class I took was FORTRAN...and > then I did a little BASIC, so this C code stuff is all new to me and it's > been a real learning experience. > I have done quite a lot of time-related work on the Arduino and here are some suggestions: -- Use the Arduino Leonardo or Micro board rather than the Uno. These use the 32u4 processor rather than the Uno's 328p. The 32u4 has integrated USB for the programming port, freeing up the hardware serial port to communicate with a GPS without resorting to resource-intensive bit-banging or interfering with the programming port. I prefer the Micro because its pins are on 0.1" centers, making it compatible with a solderless breadboard. -- For NMEA communication, use Mikal Hart's TinyGPS++ library, available at http://arduiniana.org/libraries/tinygpsplus/ This handles all the parsing of both standard and non-standard NMEA messages, You can use this in conjunction with the standard Time library to convert GPS time to a unix-like date and time structure. Contact me off-list if you want code examples. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Three-cornered hat on timelab?
On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart wrote: > So, back to my question: Where are the large ionospheric phase moves? > This question has been causing me doubt since I started on this project. > Or don't I still have enough data collected for this to happen? > > Bob > Bob, my test setup is a good deal simpler than yours, but attached is a plot that I think shows the variations you are looking for quite clearly. This is data from my homebrew GPSDO, which uses an Adafruit non-timing GPS module and a run-of-the-mill surplus OCXO. The plot records the phase comparator output over a period of about 1 week. The time constant of the PLL is 1024 seconds and it is plotting the 5-minute average TIC values. The full horizontal scale is 24 hours. The vertical scale shows the data from several days with the traces for successive days offset upwards by the equivalent of 40 nsec. As you can see there is pretty good correlation of the phase error from day to day and the wiggles migrate to the left a little, corresponding to the 23:56:04 siderial repeat time of the GPS constellation.This is with a pretty good antenna location, under a shingle roof in the attic. I calculate the day-to-day correlation at about 0.8. Making the time constant larger increases the variations somewhat, because the loop does not adjust as much, and they definitely get worse if I use a less optimal antenna location. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The ultraAtomic clock for home
On Wed, Apr 5, 2017 at 7:30 AM, Bob kb8tq wrote: > I’m still a bit unclear on how many people will set up a wall of clocks > running > on a dozen or so time zones. Obviously the people making clocks are > very much in favor of doing that > It's probably for flashy newsrooms, where they like to have clocks with the time in London, Moscow, Tokyo, etc. It's nice to have all the second hands jumping simultaneously! The challenge there is to keep the clocks correct for summer time, which changes on different dates in Europe and of course in the other direction in the Southern Hemisphere. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP-59309A Clock counts only seconds
The 14SO package is still in production, HEF4011B $0.37 ea from Digikey. You should be able to get a breakout adapter if you need the DIP. On Mon, Apr 3, 2017 at 7:43 PM, Jeremy Nichols wrote: > I have a new-to-me HP-59309A HP-IB Digital Clock. The clock works on both > the internal crystal oscillator and on an external 10 MHz standard (GPSDO). > However, it counts only to 60 seconds and then repeats without updating the > minutes digit. The TIME SET (FAST and SLOW) push-buttons work but again, > the count will not update minutes and hours, only seconds. The DAY SET > procedure works correctly for days and months. All the other switches and > buttons do what they are supposed to do. Using my 10526T logic pulser I can > force the minutes and hours counters to work. The power supply is in good > condition (after replacement of a few components) and I see no other > problems (yet). > > Tracing the clock signal through the logic circuitry brought me to U3 on > the A4 board. This (U3) is a 4011 quad 2-input NAND gate in a 14-pin DIP > package. It "connects" the seconds counter to the minutes counter and > appears to have failed. One of the people on the email list < > hp_agilent_equipm...@yahoogroups.com> commented that the 4000 series CMOS > chips have a known limited lifetime. Since these parts are no longer in > production, the writer expressed the concern that any parts I might find to > buy may be DOA. > > Before I go hunting for parts, I'd appreciate hearing from anyone in the > group who has experience with the 59309A Clock and/or the 4000-series CMOS > family. In particular, are there modern equivalents to my 4011 chip? If the > 4000's really do have a limited lifetime I'd rather use a substitute. > > Jeremy, N6WFO > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts equipment verification from scratch (was: WTB: GPSDO)
On Mon, Mar 20, 2017 at 4:14 PM, Mark Sims wrote: > $3 for an Arduino chip on a PCB with proto area from China (should have > bought a lot more when they were available),$10 for a small ovenized 5V > TTL output OCXO (also should have bought a lot more), and $5 for misc > parts (OK, beer money not included in the BOM). Batteries not needed, > powered off USB. Hi Mark, Did you use the Arduino's PWM output plus a LPF for the DAC, or a separate DAC? If PWM, did you have problems with noise or sensitivity to the USB-provided supply voltage? Also I have found that not all computer USB ports can supply enough warm-up current for a 5V OCXO. Or did you use a hefty USB charger and miss out on the ability to get logging info back over the USB port? -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Smart Phone time display accuracy...?
There are GPS apps for phones such as GPS Test Plus for Android that display the time as received from the phone's GPS. I'm not sure if phones' GPS modules produce a PPS output, but it would be cool if an app could send a tick to the phone's speaker/headphones on the second. > > Le 16 mars 2017 à 03:32, Mike Baker a écrit : > > > > Hello, Time-nutters-- > > > > Any thoughts on what the likely accuracy of smart phone time > > displays might be? > > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bye-Bye Crystals
For other common crystal frequencies, let's not forget 3.579545 MHz and 4x that - NTSC TV color burst and others listed here... https://en.wikipedia.org/wiki/Crystal_oscillator_frequencies On Tue, Mar 14, 2017 at 3:39 PM, Attila Kinali wrote: > On Tue, 14 Mar 2017 13:39:02 +0100 > Magnus Danielson wrote: > > > Some claims that MEMS will kill crystals. It will surely eat a good > > market share, but I think there is applications where MEMS is not mature > > enough compared to crystals. > > MEMS is quite mature, it's just that it is playing a different game. > While with quartz (and other piezoelectric crystals) we know how > to design a crystal to frequency, things aren't so simple for MEMS. > Simply scaling the design doesn't work apparently. > > What they instead do is to use the MEMS oscillator as a reference > for a PLL locked VCO. As the whole thing is going to be a few mm^2 > of silicon anyways, reserving some µm^2 for the PLL and VCO don't > cost much. And it gives the ability to "tune" the oscillator > for the frequency needed after production (the same technique is used > with "programmable" crystal oscillators). Of course, having a PLL, > mostly a fractional-N PLL, causes a lot of spurs in the output, > which can cause problems, depending on the application. > > The big promise of MEMS oscillators was, that they'd be cheaper (due to > integration in silicon) and used less power. As far as I am aware, > neither promise could be upheld. MEMS need a quite different production > process than normal digital electronics, hence it's usually more economic > to have the oscillator on a different die than the digital chip. As for > power consumption, the low power MEMS are about at the same level as the > low power 32kHz crystal oscillators (and also in the same frequency). > One place where MEMS are exceedingly good is temperature characteristics. > Silabs demonstrated an oscillator, which, prior to any compensation, > exhibited only <5ppm shift over the full temperature range. > > > As for the demise of single quartz crystal units, I think that is not > going to happen any soon. It is rather that the economics shift. Most > of the single crystals are used as reference oscillators for digital > and analog/RF chips. Ie most these chips have an internal oscillator > that uses an external crystal to drive their internall VCO+PLL. > As the crystal frequency is dictated by the frequencies these chips > have to generate, there is a kind of standardization going on due to > the limited number of protocols that need special frequencies. Two very > common frequencies are 12MHz, for USB, and 25MHz, for Ethernet. > 16MHz is base for CAN, some Wifi chipsets and USB as well. Then there > are a couple of frequencies that are related to GSM, UMTS and the various > other telephone standards. There are maybe a handfull of these frequencies, > which "everyone" needs (ie are used in many high volume products). These > are > the crystals we will be able around for the forseeable future. There are > other frequencies that are less used, which you will still get, but need > to pay more or are made to order. Frequencies for protocols that are > not used much anymore, or can be easily generated from another frequency > that is more common, are bound to die out (as has happend with all those > UART crystals, which are only used in legacy systems or for historical > reasons). > > > For specialized applications, where the crystal is not directly interfaced > to a chip that provides the oscillator, it is more convenient for the > designer to just use a complete oscillator than to design his own > oscillator > with all the problems that it involves. Getting such a device reliable to > work in production volumes is nothing an average engineer without prior > experience in can just pull off. Heck, I design my stuff to use oscialltors > instead of crystals, because that's one thing less I have to care about. > But even with these oscillators, there is only a limited number of > frequencies > that are easy to get. Those are again the standard frequencies from above, > and a couple of round numbers (like multiples of 10MHz) > > > Attila Kinali > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bye-Bye Crystals
On Mon, Mar 13, 2017 at 6:05 PM, Jim Harman wrote: > Some of the Arduino boards, the Leonardo for example, use ceramic > resonators, Sorry, the Leonardo does have a crystal. The original Uno had a resonator. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Bye-Bye Crystals
On Mon, Mar 13, 2017 at 4:53 PM, jimlux wrote: > I think the Arduino, for instance, uses a crystal (and the oscillator > electronics are inside the Atmel part) You're right. Some of the Arduino boards, the Leonardo for example, use ceramic resonators, which make them truly awful for timekeeping applications. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Temperature (environmental) sensors
These https://www.adafruit.com/products/381 are .0625C resolution, 1-wire interface (temp only) This one https://www.adafruit.com/products/642 has Teflon insulation, for use at higher temps Or this one, Temp/humidity with I2C interface https://www.adafruit.com/products/1293 On Tue, Jan 3, 2017 at 11:19 AM, Adrian Godwin wrote: > All these (including the one I linked) seem to be 0.5C only. > > This one gets to 0.2C : http://www.ti.com/tool/hdc1010evm > > On Tue, Jan 3, 2017 at 4:09 PM, Paul Alfille > wrote: > > > If you don't mind using 1-wire sensors, there are many nice choices, > like: > > > > http://www.embeddeddatasystems.com/Environmental-Sensors_c_44.html for > > temperature/humidity/barometric pressure... > > > > > > > > On Tue, Jan 3, 2017 at 10:22 AM, jimlux wrote: > > > > > On 1/3/17 7:08 AM, Tom Van Baak wrote: > > > > > >> I have some high-end temperature and pressure instruments. But for > > casual > > >> use in my home and mobile timing lab I use Sparkfun Weather Stations. > > The > > >> old URL is: > > >> > > >> https://www.sparkfun.com/products/retired/10586 > > >> > > >> > > > Replaced by > > > https://www.sparkfun.com/products/12081 > > > which doesn't have the USB. > > > > > > By the time you add a board with a processor, you're in the $50 range.. > > > > > > I use these at work: > > > > > > https://www.lascarelectronics.com/easylog-data-logger-el-usb-rt/ > > > Well, actually I use the EL-USB-2-LCD.. which logs to internal memory > and > > > can't log/unload data at the same time and which requires a windows > > program. > > > > > > That said, they work well, come with a traceable cal certificate, etc. > I > > > don't know that they do 0.1 degree (the data sheet says 0.5C, and I > think > > > that's the logging accuracy), and, well, humidity sensors are of > dubious > > > accuracy away from the middle of the range > > > > > > https://www.lascarelectronics.com/easylog-data-logger-el-usb-2-lcd/ > > > > > > > > > > > > > > > > > > > > > > > > It's USB, talk-only, one reading a second, temperature, pressure, > > humidity > > >> -- about as simple as you can get. Perfect for data logging along with > > >> frequency standards, GPS, counters and such. > > >> > > >> But they don't make 'em anymore. My question is what similar > > >> well-engineered, talk-only, serial or USB, > temperature-pressure-humidity > > >> sensors have you run across and could recommend? Not to be picky bit > no > > >> cheapo 1C or 0.5C sensors; 0.1C or better is ok. > > >> > > >> I know it's "easy" to throw one together with an Arduino, but I'm > > looking > > >> for something pre-packaged, something that reliably works, > > out-of-the-box. > > >> I have backup plans but hope someone on the list knows some products > > they > > >> have used and would recommend. > > >> > > >> We could extend the discussion to voltage and power monitors too. Or > > some > > >> kind of universal sensor TAPR project. But for now, let's just keep it > > to > > >> simple air / environmental sensing. > > >> > > >> Thanks, > > >> /tvb > > >> ___ > > >> time-nuts mailing list -- time-nuts@febo.com > > >> To unsubscribe, go to https://www.febo.com/cgi-bin/m > > >> ailman/listinfo/time-nuts > > >> and follow the instructions there. > > >> > > >> > > > ___ > > > time-nuts mailing list -- time-nuts@febo.com > > > To unsubscribe, go to https://www.febo.com/cgi-bin/m > > > ailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > > mailman/listinfo/time-nuts > > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?
You could try hooking up a transformer with a 20V secondary as an autotransformer to reduce the line voltage. On Fri, Dec 30, 2016, 9:09 PM Bob Stewart wrote: > If you can touch the heat sink for 2 seconds, you're made of sterner stuff > than I am! They run very hot. It's a good idea to get a GPIB extender so > your GPIB cable can clear the heat sink. Somebody, can't remember who, > worked up a nice looking conversion to a pair of switching supplies. I > bought a couple of the supplies from ebay, but that project hasn't shuffled > to the top of the list, yet. Maybe the next time I forget and reach back > there and get burned... > > Bob > > > > From: Dr. David Kirkby - Kirkby Microwave Ltd < > drkir...@kirkbymicrowave.co.uk> > To: Discussion of precise time and frequency measurement < > time-nuts@febo.com> > Sent: Friday, December 30, 2016 5:58 PM > Subject: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob > for the 5370B TI counter? > > I bought a 5370B TI counter which arrived today. It needs a bit of TLC, but > nothing too bad. But one of the rotary knobs is incomplete. Does anyone > have a > spare knob? Contact me off list if you do. > > I had one of these things about 10 years ago. I have forgotten how to > drive it. > > It is running very warm. I can hold my fingers on the heatsink for only a > couple > of seconds - not a very scientific test I must admit. > > Obviously the mains voltage varies a bit, but it is usually well over the > 230 > VAC we are supposed to be. I just measured it at 248 VAC. Unfortunately I'm > right on top of the 11 kV transformer, so other properties around me > probably > get poorer voltage regulation, but a few less volts. > > > Dave > > > -- > Dr. David Kirkby Ph.D CEng MIET > Kirkby Microwave Ltd > Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 > 6DT, UK. > Registered in England and Wales, company number 08914892. > http://www.kirkbymicrowave.co.uk/ > Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please) > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Lady Heather for homebrew GPSDO
On Sun, Dec 18, 2016 at 1:06 PM, Mark Sims wrote: > Binary or NMEA you need routines like send_msg_start, send item (like > integer, float, double), send_msg_end. For received messages you need > things like get_message, get_item_from_message, etc. The code to do that > is not much more complicated for a binary protocol or an ASCII one like > NMEA. > One factor that leads me to prefer NMEA is that my GPS already produces it, so all I would have to do for the satellite, time, and other GPS data would be to send the NMEA sentences from the GPS to the host port, no parsing and reformatting required. In order to inject GPSDO data into this stream, I would have to implement an NMEA multiplexer and construct the new sentence(s) as you describe above.Of course I would still need an NMEA parser in order to interpret commands from the host, but in the Arduino world there is TinyGPS++, a very handy open source library for this. I see that although the Z3801A's SCPI messages would be pretty easy to implement, there are several inconvenient or limiting aspects to this interface. (please correct me if I am wrong on these) --It does not stream data the way NMEA does, so the host has to keep asking for data. --As has been mentioned earlier, most of the responses have no identifier, so both ends have to be careful not to get out of sync. --The EFC value is given as an integer percent -100 to 100, so there is not enough resolution to really tell what the DAC is doing. -- It does not have the satellite position and C/N data that is reported in the NMEA GSV sentence, so LH can't make its nice satellite plots. One thing I like about the Z3801A's format is the way the TCOD message includes brief status and alarm information, so the data doesn't get clogged with routine data but the host can tell when to request detailed information. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Lady Heather for homebrew GPSDO
Hi all, I have experimented with LH 5 just monitoring a GPS receiver and am very impressed with the results. As a next step, I would like to use LH to monitor a homebrew GPSDO, and I think it would be easier to modify the GPSDO firmware to emulate an existing device rather than customize LH to work with the logging data that my system currently produces. In addition to NMEA data from the GPS, my system can output the DAC and TIC (phase error) values as well as the temperature, Since I control the firmware, I can produce pretty much any data format as long as it is clearly documented, but I would prefer a text-based rather than binary protocol and not to have to reformat all the NMEA data. Does this approach make sense, and if so which of the several standard GPSDOs would it be best to emulate? Thanks in advance for your insights -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1PPS to 32.768 khz
On Thu, Oct 20, 2016 at 7:08 AM, Bob Camp wrote: > One problem with a PLL and a 1 Hz input are the values of components > you get in the loop. > The other issue is the cost of the VCXO that will get > you to 32,768 KHz. > As I mentioned earlier, the DS3231 chip (about $6.50 qty 1 or $17.50 on a breakout board) might be a reasonable approach for this. It is a self-contained 32.768 KHz TCXO that lets you vary the frequency in steps of 0.1 ppm using its I2C interface. Left to its own devices, it measures the ambient temperature and switches its on-chip capacitors in and out to control its frequency. It has both 1 PPS and 32,768 Hz outputs. Connected to an Arduino-class processor, you could measure the time delay between its PPS and the PPS from a GPS and tweak the oscillator accordingly, making a complete 32.768 KHz GPSDO including the GPS with just 3 chips. And you get RTC functionality and battery backup circuitry thrown in for free. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1PPS to 32.768 khz
Hi Lee, It's not exactly what you asked for, but for your clock you might give this a try, or consider using the underlying DS3231 chip directly. https://www.adafruit.com/product/255 It is basically a much more accurate and stable than usual 32KHz oscillator, with a TCXO that you can actually tweak programatically with a resolution of about 0.1 ppm. On Tue, Oct 18, 2016 at 10:03 PM, Lee - N2LEE via time-nuts < time-nuts@febo.com> wrote: > First let me say this is first time I have posted to the group so go easy > on me. :) > Secondly I want everyone to know that you guys make me feel so NORMAL for > wanting to use and understand accurate timing devices. > > I thought there was something seriously wrong with me now I know there are > others > affected with the same disease. hehe > > Now my questions. > > 1. Does anyone know of a device that will take a 1PPS GPS timing signal > and generate a 32.768 kHz sine wave output ? > I have big digital clock that uses an 8 bit micro processor and an > external 32.768 crystal. Obviously the external crystal is > awful for accuracy. > > I have searched every where using as many search terms as I can think of > and can’t believe there is not a device that performs > this function. > > I have found a couple of Epson RTC chips that might come close that 1pps > but I don’t think that corrects the 32khz just the clock time. > > 2. 10 Mhz Freq Standard > I am not in the same league as the majority of the list members and just > starting to dabble in GPSDO stuff. > I have tried to find a thunderbolt as a starting device but it appears > those are either dried up or people want too much money. > > I wanted to get the opinion of anyone who has tried the Leo Bodnar GPSDO ? > For the money it appears to offer a beginner a lot of features. > > Thanks and reading the daily digest of what you guys are working on. > I have a feeling if I am not careful you guys could cost me a lot of > money. hehe > > > Lee > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Measure GPSDO stability with minimum resources?
On Wed, Oct 5, 2016 at 6:46 PM, Bob Stewart wrote: > What I'm really looking for is a way to do everything in the PIC. I've > been experimenting with saving the DAC value in a circular queue every 20 > seconds for 60 minutes, and plotting the difference value between the head > and tail of the queue every second. After posting this question, I took > another look at the overall behavior and decided to cut the queue size down > from 60 minutes to 5. Hi Bob, Unless the oscillator is still warming up, 5 minutes or even 60 is way too short a time to look at aging. For aging, you will want to look at the change in DAC values over several days at least. Looking at the current value and one in the past will give you a feel for what is going on, but then you are discarding all the intermediate data. You really want to do a least squares fit using as many data points as you can handle, Check Wikipedia under Linear Least Squares for an example. What sort of phase detector are you using? If you want to see whether the system is locked, you may be better off looking at the phase detector signal.and declaring a lock if the low pass filtered phase error stays within a pre-determined range. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] ADC sample voting algorithm?
On Wed, Oct 5, 2016 at 7:45 PM, Nick Sayer via time-nuts wrote: > I notice periodically that the phase measurements seem “noisy.” You can > see that over the course of several seconds the value doesn’t change, then > it jumps a bunch and then comes right back. > Hi Nick, At one point I had a problem with noisy phase readings where the "noise" took the form of an occasional reading that was low by up to about 50 counts. These events were quite rare - less often than once per hour on average. After much head-scratching, it turned out that I had an interrupt conflict that sometimes caused the PPS interrupt to be delayed, Because the ADC was triggered inside this routine, the analog signal had drooped a little before the ADC was triggered. I was able to completely solve this by setting up the ADC sample/hold and conversion to be triggered directly by the PPS signal, thus eliminating any dependency on the interrupt latency. The PPS still generates an interrupt, but in the interrupt routine, all I have to do is wait for the ADC to finish, clear the Done bit, and reset the trigger. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Measure GPSDO stability with minimum resources?
On Wed, Oct 5, 2016 at 1:37 PM, Bob Stewart wrote: > For my GPSDO, I need to calculate the OCXO aging for holdover projection > purposes as well as get some figure of merit for the recent past of the > OCXO stability. Do you have a serial port or some way of generating a logging stream? If so, one low-overhead way to track the aging is to compute an average DAC value and periodically "print" the result to the serial port. I have found that a 3-hour average works well for observing aging. Each second you simply add the current DAC value to a Long and after 3 hours divide by 10800, print the result, reset the total, and repeat. It is helpful to also include the current time. This could be extracted from the GPS NMEA data or simply be seconds since startup. If you separate the values with a Tab and end each set of values with a newline, you can capture the data with an attached PC, copy/paste to Excel, and analyze it there. The trend line feature in Excel's chart will compute and display a least square fit to the aging. If you don't want to keep the monitor connected full time and you have some extra RAM or preferably EEPROM, you can store historic average values in a circular buffer and print one of the values every second. 288 bytes will store 18 days worth of 16 bit 3-hour averages. My system, based on the one posted here by Lars Walenius some time ago,collects 144 sets of 5-minute averages (12 hours worth) and another 144 sets of 3-hour averages. It spits out one line of logging data each second. The first part of each line has the current data, and the second part has either one of the 5-minute sets or one of the 3-hour sets. So 5 minutes worth of logging data has 300 lines, showing current data plus 5-minute averages for the past 12 hours and 3-hour averages for the past 18 days. All this, including the GPSDO code, fits comfortably in a 32u4-based Arduino Micro, which has 32K of program memory, 2.5K of RAM, and 1K of EEPROM. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Q/noise of Earth as an oscillator
On Wed, Jul 27, 2016 at 11:33 AM, Chris Caudle wrote: > Who has a globe on magnetic bearings in a vacuum chamber and will run the > experiment for us? > The superconducting gyroscopes in the Gravity Probe B satellite did an extraordinary job of eliminating frictional and other losses in a spinning object, with a spin-down time constant of 15,000 years. https://einstein.stanford.edu/TECH/technology1.html -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Visiting Greenwich
Those in Australia might want to check out the traveling "ships, clocks, and stars" exhibit at the Australian National Maritime Museum in Sydney through Oct 30. I saw this earlier this year when it was in Mystic Connecticut and found it very interesting. It is also appropriate for non Time Nuts. It presents a good overview of the quest for longitude at sea and features beautiful working replicas of Harrison's clocks. On Wed, Jul 6, 2016, 7:46 PM Morris Odell wrote: > This is a terrific thread. I have been to Greenwich too and also some of > the > clock exhibits in London. There's a beautiful pendulum master and slave > clock set up in the British Museum, and there's an original huge Caesium > (British spelling!) frequency standard in the Kensington Science Museum. > The last time I was there in 2013 there was also a special feature > exhibition about Alan Turing and the Bletchley code breakers. I did pass > through Bletchley station on the train about 20 years ago when I was in the > UK but regrettably didn't have the time to stop there. I can recommend the > climb up the hill at Greenwich to anyone - it's definitely worth the > effort. > They didn't allow photography of the Harrison clocks but I did manage to > sneak one or two before the minder got to me :-) > > I'd love to have a genuine electro-optical speaking clock. There's one in > the Australian Telecom museum not far from where I live. There's also a > terrific display of a complete electromechanical telephone exchange > including a speaking clock in the telecommunications museum in Stockholm > but > as I don't speak Swedish I couldn't understand what it was saying. I've > just finished making a speaking clock using more modern technology, it uses > a 30 year old speech synthesizer chip and sounds just like Stephen Hawking. > > Morris > Melbourne, Australia > - >Date: Wed, 6 Jul 2016 10:42:19 +1000 > From: Jim Palfreyman > To: Discussion of precise time and frequency measurement > > Subject: Re: [time-nuts] Visiting Greenwich > > Speaking of "speaking clocks" - here's two photos of the ones that used to > be used in Australia: > > https://en.wikipedia.org/wiki/Speaking_clock#Australia > > The top photo with rotating optical disks is a gorgeous piece of machinery. > > The one below - I have one, and I keep it running. > > :-) > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS altitude somewhat wrong?
On Wed, Jun 8, 2016 at 4:33 PM, Van Horn, David < david.vanh...@backcountryaccess.com> wrote: > Backcountry Access, Inc. > 2820 Wilderness Pl, Unit H > Boulder, CO 80301 USA > Google Earth has the elevation of this address as 5272' which is a good deal closer to your reading... -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Fwd: Home-brew GPSDO
-- re-posting with smaller attachment -- On Thu, Mar 17, 2016 at 12:40 PM, Logan Cummings wrote: > I was planning on using the Due's ADC to measure the voltage on the > integrator capacitor, but hadn't decided yet about a "good" current source > vs. a series resistor on the output of an XOR or DFF phase comparator to > put charge on the capacitor. > > Hopefully someone else can chime in with some better links and circuit > descriptions. > You might want to consider the approach used in the attached schematic and write-up. This is for an Arduino Micro based system, but you should be able to adapt it to work with the Due. The simple RC network works OK if you can set the ADC full scale range to 2.5 V or less, but shows some nonlinearity at the high end due to the exponential charging. I have been experimenting with a circuit that uses a better current source, which I can pass along if you are interested. So far the performance seems to be about the same as this simple circuit. -- --Jim Harman -- --Jim Harman Arduino GPSDO Schematic v4.pdf Description: Adobe PDF document Arduino GPSDO notes.docx Description: MS-Word 2007 document ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Conditioning Rubidium Oscillators
Attila and Bruce and Adrian, You are right, I stand corrected. Despite the talk in the app note about aging rates and calculating the average slope of the frequency offset, and about how m represents the rate of change of the frequency offset, when you dig into the formulas, they are doing a linear fit to determine the slope of the phase, which of course corresponds to the frequency offset itself and not its rate of change. Sorry for any confusion I may have caused. Attila, good suggestion on the Kalman filter. I will educate myself about that. On Tue, Mar 15, 2016 at 8:30 PM, Bruce Griffiths wrote: > They actually determine the phase offset and rate of change of phase (i..e. > frequency offset and not frequency drift as claimed in the paper) from a > linear > regression fit to a sequence of phase differences. > The results from the regression fit are then used in an adaptive PID loop. > > Bruce > > > On Tuesday, March 15, 2016 10:28:39 PM Adrian Godwin wrote: > > My understanding of the article was that although fairly simple control > > techniques such as PID were used, their innovation was to determine what > > function the loop was performing, (initial lock, stability, and > transition > > from one to the other) and to choose a set of constants for loop control > > appropriate to each type. The ideal loop characteristics are not the same > > for all of these. > > > > On Tue, Mar 15, 2016 at 7:51 PM, Attila Kinali wrote: > > > On Mon, 14 Mar 2016 19:56:42 -0400 > > > Jim Harman wrote: > > > > > > > > > Disclaimer: Control theory is not my strongest topic. I am pretty sure > > > that what I have written here is correct. But if anyone finds any > > > mistakes, please correct me. > > > > > > > On Mon, Mar 14, 2016 at 2:37 PM, Lars Walenius < > > > > > > lars.walen...@hotmail.com> > > > > > > > wrote: > > > > > I read this but couldn´t understand why this is superior to the > > > > > PI-loop > > > > > with a pre-filter? > > > > > > > http://ptfinc.com/wp-content/uploads/2016/03/App_37_RubContol-Rubidium-Con > > > trol-%E2%80%93-A-Different-Approach.pdf> > > > > > Anybody can say why? Even if regression is very useful the > limitation > > > > > > of > > > > > > > > the GPS and ionosphere will be the problem?How much better is it > > > > > > reasonable > > > > > > > > to get?? > > > > > > A PID loop adapts to a step as input faster than a PI loop. > > > To give a rule of thumb: the D part is used to predict how fast > > > the error is moving. If the error is shrinking fast, there will > > > be an overshoot once the error reaches zero. Thus the D part is > > > used to make the rate of change slower once the error becomes small.. > > > Nothing more. > > > > > > The wikipedia entry on PID controllers explains these things in > > > some detail and should help understand it. > > > > > > > I think the potential benefit of this approach is that it > continuously > > > > predicts the long term drift of the oscillator and attempts to > > > > compensate > > > > for it. > > > > > > Nope, the above appnote does not predict anything. It's not an adaptive > > > control system at all. All they do is describe an PID controller > without > > > using the common language of the control theory people. > > > > > > > If the drift is reasonably linear, this means that you can use a > > > > larger time constant in the control loop and thus be less sensitive > to > > > > short term GPS timing variations, while keeping the phase error > close to > > > > zero > > > > > > If the drift is linear, then the D part of the PID control loop will > > > actually slightly increase the error compared to a PI controller. > > > > > > Proper adaptive control systems can also model higher order (ie changes > > > that have components with a second or third (or higher) derivative) and > > > the more fancy stuff even non-linear "drift". > > > > > > But the math behind that is not easy, and you need to have a good idea > > > what the system (including reference, "plant", "sensor" and noise > sources) > > > looks like to build a control loop that improves on the PID controller. > > > It's also quite easy to botch it up and make something that performes > > >
Re: [time-nuts] Home-brew GPSDO
On Thu, Mar 17, 2016 at 4:38 PM, Nick Sayer via time-nuts < time-nuts@febo.com> wrote: > Anyway, my hat’s off to Jim - it’s an extremely elegant mechanism, and it > was inexpensive both in parts and board space to add. Thanks for the kudos Nick. The design is what I just posted on another thread if you want to see the schematic. Credit for the design actually goes to Lars Walenius, who posted it here a couple of years ago. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Conditioning Rubidium Oscillators
On Mon, Mar 14, 2016 at 2:37 PM, Lars Walenius wrote: > I read this but couldn´t understand why this is superior to the PI-loop > with a pre-filter? > > > http://ptfinc.com/wp-content/uploads/2016/03/App_37_RubContol-Rubidium-Control-%E2%80%93-A-Different-Approach.pdf > > Anybody can say why? Even if regression is very useful the limitation of > the GPS and ionosphere will be the problem?How much better is it reasonable > to get?? > I think the potential benefit of this approach is that it continuously predicts the long term drift of the oscillator and attempts to compensate for it. If the drift is reasonably linear, this means that you can use a larger time constant in the control loop and thus be less sensitive to short term GPS timing variations, while keeping the phase error close to zero Of course if the oscillator drift is not predictable, this won't help and might even make things worse. I have done some experiments with an OCXO and a controller design similar to the one Lars posted some time ago. I plotted the trend in the 3-hour average DAC values over many days and used Excel to do a least-squares fit to that data. As long as the oscillator is powered on continuously, this gives an R^2 of over 90%, so the linearity of the drift is very good. If I use this slope as a correction factor, i.e. adding X DAC counts per day to the output of the PI control algorithm, it significantly reduces the average TIC error at long time constants -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] When does NIST change to DST?
WWVB has sent the signal to switch to DST but the website has not changed yet. On Sun, Mar 13, 2016, 10:11 AM wrote: > I noticed that NIST, at http://nist.time.gov/ , is still sending standard > time. When do they change? > > John WA4WDL > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] PRS 10 and serial port communication
Actually a null modem is just the device that interchanges the connections, Rx to Tx and sometimes DSR to DTR and others. The inverters are needed in this case to convert zero or negative voltage levels to positive and vice versa. On Fri, Mar 4, 2016, 6:00 PM Artek Manuals wrote: > The "inverter's" went by the jargon name of "null modem" back in the day > ...if you google "null modem" you will find the wiring diagrmas for > rolling your own with a couple DB9 connectors I have to use the null > modem adapter when using a standard off the shelf serial cable with my > z3801A as well > > Dave > > > > > On 3/4/2016 2:26 PM, Philip Zahariev via time-nuts wrote: > > As already tell you I have success with inverters and now can monitor > state of PRS 10. Attached send current status for comments. Any help > appreciated. > > Best regardsPhilip > > > > > >From: Hal Murray > > To: Philip Zahariev ; Discussion of > precise time and frequency measurement > > Cc: hmur...@megapathdsl.net > > Sent: Friday, 4 March 2016, 11:43 > > Subject: Re: [time-nuts] PRS 10 and serial port communication > > > > > >> As I already write PRS10 is configured as serial communication. With > >> oscilloscope I can see serial signals, but when enter this signal in > >> computer with TTL level USB2serial converter all information is > repeatable > >> character unknown for me and not as described in manual. > > > > You may need to add or remove an inverter in there. > > > > Most serial ports on microprocessors and USB to serial chips are > expecting a > > TTL to RS232 level shifter and the standard level shifter chips all have > an > > inverter. If there are 0 or 2 inverters it should work. > > > > Some GPS modules don't have any level shifter. Some devices include an > > inverter but not the level shifter. That doesn't meet specs but it > generally > > works if you connected it to a real serial port (with level shifter). > > > > I would connect a scope to the output side of the USB to serial chip and > send > > it occasional characters and use that as a reference for what a > character is > > supposed to look like. > > > > Then look to the input side and see if it looks similar. In particular, > > verify that the idle level is the same. Then check the baud rate and > parity. > > > > > > > > > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > -- > Dave > manu...@artekmanuals.com > www.ArtekManuals.com > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] PRS10 and missing serail port communication
Make sure Rx on the converter is connected to Tx on the PRS10 , Tx to Rx, and the polarity is correct. The transmit lines should be at 0 V when idle. Not sure about the PRS10, but official RS-232 requires the idle (Mark) voltage to be -3 or lower. On Thu, Mar 3, 2016, 5:00 PM Philip Zahariev via time-nuts < time-nuts@febo.com> wrote: > I forgot to tell you, that during tests I use TTL (5V) level USB to serial > converter. > > -Original Message- > From: Mike Cook [mailto:michael.c...@sfr.fr] > Sent: Wednesday, March 2, 2016 11:15 PM > To: Philip Zahariev; Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] PRS10 and missing serail port communication > > > > Le 2 mars 2016 à 15:50, Philip Zahariev via time-nuts < > time-nuts@febo.com> a écrit : > > > > Hello group, > > > > Recently obtained from eBay PRS10 marked as no-lock. Of course my > > first task was to open device and see what is current state of lamp, > capacitor and etc. > > surrounding parts. My surprise was that all things look pretty good > > (of course is used). And frequency is not correct :-) Actualy first > > 1-2 minutes frequency is pretty close to 10 MHz, but after all thing > > is ready (hot) frequency go far away. > > > > My questions: > > > > 1. How bright should be the light from lamp? Few seconds after power > > is applied to device lamp start shining, but I can see only if room > > light is close to dark or if I use magnifying glass focused on hole for > inspection. > > > > 2. I cannot communicate with PRS10 using RbMon10 (software from SRS). > > Only obtain repeatable characters from PRS10 if start terminal program > > with baud rate 9600 baud, 8 bits, no parity, with 1 start and 1 stop > > bit and no answer of any command according manual. Double checked > > according schematics and port is configured as serial. Any advice how to > obtain communication? > > RbMon10 will normally configure the PC serial port correctly. So it > might be due to voltage levels? The PRS10 port is 0-5V TTL and not the > usual +/-12V RS232 levels. > Also it requires XON/XOFF protocol. That would need to be configured for > a Terminal prog connection. > > > > > > Best regards > > Philip > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > "The main function of a modern police force is filling in forms." > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Next step up from basic GPS/PPS timekeeping
On Thu, Feb 25, 2016 at 1:08 PM, Neil Green wrote: > I’ve decided to build this: > > http://www.hackersbench.com/Projects/1Hz/ > > which has an easy to follow diagram. Parts have cost less than £5. I’m not > expecting great things from it by any means, but it’s something I can get > my head around and should improve my understanding (a little). > Good start! Once you have built it and observed how sensitive it is to temperature variations, you might want to take a look at this: https://www.adafruit.com/products/3013 This breakout is based on the DS3231 chip, which is a temperature compensated 32 KHz real time clock with a built in crystal and optional battery backup. It also has a 1 pps output. It is reasonably stable and accurate out of the box, but if you want to adjust it you can send it commands from a microprocessor that tweak its frequency up and down in increments of about 0.1 ppm (about 3 seconds per year). It does this by switching in and out tiny on-chip capacitors. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Next step up from basic GPS/PPS timekeeping
On Wed, Feb 24, 2016 at 2:53 PM, Nick Sayer via time-nuts < time-nuts@febo.com> wrote: > I can measure 1 ppb, but it takes 1000 seconds to do it ... My > understanding is that better GPSDOs are able to provide for more granular > phase detection. It doesn't take a lot of hardware to get about 1000x better than that. The Arduino-based design Lars Walenius posted a while ago can take a reading every second with a resolution of about 1 nsec. It uses an HC390 divider to reduce a 10 MHz OCXO to 1 MHz. The 1 MHz and pps pulse from the GPS feed an HC4046 phase comparator, producing a 1 pps pulse 0-1 usec wide, with the width proportional to the phase difference. This feeds one diode and an RC network to make a ramp with its peak height (0 - 2.5V) proportional to the phase difference. This feeds the processor's 10-bit A/D converter, which is set for 2.5V full scale.The 1 pps signal triggers the A/D, capturing the height of the pulse. One more resistor discharges the capacitor between pulses. Because the discharge time constant is much longer than the interrupt latency and A/D conversion time, the A/D captures the peak value. I have been experimenting with this design for some time, with a lot of learning along the way. Of course there are always potential improvements, but the current design works surprisingly well. If someone can provide access to a good set of test gear (I am in CT), I could better quantify the performance. My latest schematic is attached. -- --Jim Harman Arduino GPSDO Schematic v4.pdf Description: Adobe PDF document ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Newbie questions
I am a relative newbie here myself, but at the risk of starting a firestorm, I would take issue with some of what Bob says below. See comments interspersed. On Wed, Jan 27, 2016 at 7:43 AM, Bob Camp wrote: > Hi > > Ok, so let me answer the questions you *should* have asked: > > (They are in no particular order. Number 3 probably should come first) > > 1) Is the gear I have enough to do this project? > > No, you will need some sort of frequency / time standard. An atomic > clock of some sort is pretty much a minimum. You probably also need > a working GPSDO (or set of them) for comparison as well. You will also > need a working / modern precision counter that will give you data down > in the < 100 ps range. > This depends on your answer to #3 below. For my GPSDO, project, all I have is a scope, DMM, and PC. I can't measure ADEV, but by setting the time constant of my filter to 1000 sec and monitoring the TIC output I can be pretty certain that my local reference is well within 100 nsec of the "true" time. > > 2) How will this ultimately be built? > > At the very least, you will be building this with surface mount devices. > If it’s a scratch build, you will be dealing with fine pitch parts. That > gets > you into a whole bunch of gear. It also gets you into a very real “is this > fun or not” sort of question. > For my GPSDO I started with and Arduino board and a solderless breadboard. Anything with an SMD is on a purchased breakout board that spreads its pins to 0.1" centers. You do have to be careful to keep the wires short when working with fast rise times. I migrated this to a solder-type breadboard that mimics the layout of the solderless board and it is working fine. > > 3) What *is* the goal? > > "I’m going to make dinner” is the start of a process. It’s not enough of a > goal to accomplish the task. Starting the task with a general objective is > fine. > It does need to be refined a bit before you go much further. > Agreed. > > Is this what most of us would call a GPSDO (self contained box) or is it > something with a PC in the middle of it? > Mine runs either stand-alone or with a PC to monitor it. > > Is this an OCXO based “precision” device or is it something more simple? > I used a $25.00 surplus OCXO. Eventually I may invest in something better but then I would have to get a timing GPS to go with it. Currently I am using the $40.00 Adafruit module. > > Is a pure software solution good enough? > Mine is almost all software, but it has a TIC that consists of a 74HC4046 phase detector chip, a diode, a cap, and 2 resistors, feeding an A/D input of the Arduino processor board. This gives a resolution of 1 ns. > > Each of those decisions (and that’s by no means a full list) will send you > off > in a very different direction. > For sure! > > 4) How long is this likely to take? > > Best guess based on the others who have done the same thing - several > years. > I have been at it on and off for about two years but I have learned a lot along the way. > > 5) How much is this likely to cost? > > If done the way others have done it, several thousand dollars up to > quite a bit more than that. > My total investment (not including the scope, DMM, and laptop PC) is under $200. > > 6) How much research is involved? > > Quite a bit. The information you need is scattered all over the place. > Figure > that you likely will read at least several hundred papers. There is a whole > statistical language that is unique to these gizmos. This is *not* a > follow a > set recipe sort of project. > Again, depends on your answer to #3. I started with a working design and code and modified it to suit my fancy. I am pleased with the result. It keeps the brain cells firing. > > Lots of fun !!! > Absolutely!! -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Newbie questions
On Tue, Jan 26, 2016 at 7:04 PM, wrote: > I am trying to learn more about electronics and start doing > hardware projects. I have never been into model building or anything > similar, > so my construction skills are lacking. I understand a lot of things in > theory, > but practice still eludes me. > To get a better background in electronics, I would highly recommend "The Art of Electronics" by Horowitz and Hill. The long awaited and fully updated 3rd edition came out just last year and it is well worth the $80.00 price. As a person who has worked with electronics on and off since 1960, I can say it teaches electronics the way I wish I had been taught. It has a strong emphasis on practical applications and assumes only high school math. Some here may pooh-poo it, but to get started building useful electronic systems I would recommend the Arduino platform. Fully assembled processor boards are about $25.00 from reputable suppliers and have plenty of I/O pins to get you started. On some versions of the processor you can expand the I/O by adding "shields" which mate to headers on the processor board. All you need to do to is to plug the board into a USB port on your PC or Mac and download the free IDE. Both the hardware and software are open source so you can see exactly how they work under the covers if you want. A wide variety of libraries is also available (all free) and there is a lively user community. The programming language is a stripped-down version of C++ with a bunch of simple extensions to support analog and digital I/O. Once your code is working you can either continue to power the system through the USB port or run it stand-alone with a 9V battery or wall wart. I have built a GPSDO based on the design posted here by Lars Walenius a couple of years ago. It uses the Arduino Micro processor, which is nice because it has a second serial port. This lets it get serial data from the GPS and talk to the PC at the same time. I would be happy to post the schematics and code if you are interested. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Newbie questions
GPS >> receiver is probably more complex than can be easily handled by an >> amateur so >> I am most likely restricted by available receivers. >> >> I have also read, more than once, statements in this forum that something >> or >> another could be had for some low, low price so why build it yourself? I >> think >> that there are several reasons, including but not limited to the >> following. >> >> 1. It is an interesting project. >> >> 2. It is an educational project. >> >> 3. You may have some ideas about how things could be done differently or >> better. >> >> 4. You may want some combination of features that is not commercially >> available or perhaps is not affordable even with a generous budget. >> >> 5. Many people on limited budgets are not limited by total cost, but >> rather >> by incremental cost. So, someone may not be able to afford several >> hundred >> dollars for a pre-built system. But, they may be able to afford $50 >> here >> and there. So, building it themselves is the only practical option. >> >> >> Mike >> >> >> >> >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Celestial Navigation instruction being reinstated in the US Navy
On Mon, Oct 26, 2015 at 5:20 PM, paul swed wrote: > next will be slide rules. OT, but I have recently dusted off my trusty Pickett to use at the gas station. The Prius trip computer gives miles driven since last fill-up and MPG, so miles / MPG * $/Gal = $ to pre-pay, saving a few cents/gal and a trip inside to get my change. Surprisingly accurate. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] How did they distribute time in the old days?
The Western Union clocks were still in use at broadcast stations in the early 1970s. One problem was that the reset pulse and resulting jump in time would come exactly on the hour, when you were trying to synchronize with a network news broadcast that began at the network's version of 00:00. ABC and I presume the other networks would send a tone 10 seconds before their program started, By listening to the network on the "Cue" channel, you would have a pretty good idea of when the news would start. Another system in wide use around then and still somewhat today for controlling the clocks in a large building was sold by Simplex. The building would have a master clock (set manually by the custodian or whoever) that pumped out tones at about 3 KHz over the power lines. These signals would come out a couple of minutes before the hour, presumably to avoid problems with events scheduled on the hour. The slave clocks were designed to run a little fast, and would wait at 58:00 until they received a tone to restart. I believe there was a special tone that would make the clock run "fast forward," to deal with longer adjustments for power outages and DST. One drawback of this system is that the tones sometimes leak into audio equipment, and in a quiet room they are often audible through the fluorescent light ballasts. On Wed, Oct 14, 2015 at 12:42 PM, Nick Sayer via time-nuts < time-nuts@febo.com> wrote: > > > > The WU standard time service goes back further than the turn of the 20th > century. It started in 1870. > > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] UPS for my time rack
On Sat, Oct 10, 2015 at 9:20 AM, Chris Waldrup wrote: > Has anyone had bad experience noise wise with the APC brand units like are > available on Amazon and at Staples? I'd like to get one that doesn't > generate lots of RFI. I have an inexpensive CyberPower 825 AVR UPS, The UPS does the job of keeping my computer and time-nuts gear running, but it causes an annoying amount of RFI in the AM broadcast band. The noise is radiated from the circuit that feeds the UPS. I found that plugging the UPS into a Belkin outlet strip, which presumably includes some line filtering,reduced the interference significantly. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] advice for buying VCXO
Only the first oscillator in your list is voltage controllable (VC). If you want to steer it with a GPS as we have been discussing, it needs to be voltage controllable. You will also want to consider the mounting and whether you are able to solder surface mount devices like the second one in your list. You will also need to consider what power supply voltage(s) you have available and whether you want sine or TTL output voltage. These parameters will narrow your selection considerably. Also if you have the power available you will get much better stability if the oscillator has an oven (OCXO) Pretty good surplus OCXOs are available for less than $25.00. With an OCXO you might also look for one that has a reference voltage output. If you can use this voltage to power the analog part of your tuning circuitry, you won't have to worry about the effect of power supply stability on that portion of your system. The stability of any surplus oscillator is pretty much a crap shoot. You can get them cheap but you might have to sort through a few to find one that is good enough for your purposes.. On Mon, Oct 5, 2015 at 8:22 AM, Can Altineller wrote: > Hello, > > I am want to buy some VCXO's but really simple and cheap ones. I requested > a quote from goledge.com and their prices are around 180GBP per unit, and > I > dont want to pay that much given you can buy a rubidium standard for > comparable prices. > > I looked on ebay and found those candidates: > > > http://www.ebay.com/itm/12-8MHz-NKG3001B-VC-TCXO-DIP-NDK-New-x2pcs-Oscillator-VCTCXO-VCXO-TCXO-GPSDO/310376642284?_trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D32831%26meid%3D822a498fde5a4f19b8d5909a2b8496c5%26pid%3D100033%26rk%3D1%26rkt%3D3%26sd%3D310376642284 > > > http://www.ebay.com/itm/3-PCS-TCXO-6663-12-8-TCXO-25-4-x-29-21-x-10-03-SMT-VECTRON-INTERNATIONAL-/221657383361?hash=item339bcf41c1 > > > http://www.ebay.com/itm/Free-shipping-ONE-PIECE-PRECISION-0-3ppm-12-8MHz-12-8M-DIP-TCXO-/141771669896?hash=item2102400188 > > The third one is nice, it says 0.3ppm, but I am not sure if the specs are > true. > > Any recomendations on where to source cheap vcxo or vctcxo's? 10mhz or 12.8 > mhz is ok, and <1ppm would be nice. > > Best regards, > C.A. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4046 experiment for gpsdo
On Sat, Sep 26, 2015 at 9:54 AM, Magnus Danielson < mag...@rubidium.dyndns.org> wrote: > If you have an oven, it is wise to discard beat-note frequencies outside > of some suitable range, so that it first needs to go within that range > before any attempt to lock it is done, so that worst part of the heat-up > frequency deviation and drift has ended. Yes I have found this to be very helpful. Building on Lars' implementation, my code currently does the following to speed up lockup from a cold start: 1) It sets the initial DAC value to the most recent 3-hour average value from previous runs. This is stored in EEPROM so it is remembered through power-down. On the very first run it uses half scale as a starting point. 2) It holds this DAC value until the frequency error is <= 3 counts at 5 MHz (600 ns/sec or 6x10^-7) and the TIC difference from the previous second is <50 counts (50 ns/sec or 5x10^-8). The first check is what ensures it does not try to lock on to the wrong cycle, which would be off by 5 counts or more. I usually leave the oscillator (a surplus C-MAC STP2322) powered on, so it meets these criteria right away after startup. If the oscillator has been powered off for 15 minutes, it meets these criteria in less than 10 minutes after power-up. The spec for the oscillator is that -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4046 experiment for gpsdo
Good question Will. First, it divides the 10 MHz down to 1 MHz, so the oscillator would have to be off by 10 Hz for it to lock onto the wrong cycle. Second, the full implementation also feeds 5 MHz from the oscillator into one of the processor's counters and checks the count every second. It performs several checks on this to detect if the frequency is way off, missed PPS, etc. On Sat, Sep 26, 2015, 12:15 AM Will wrote: > Hi, > > I'm new and trying to get to grips with things. > > If I understand correctly, please forgive if I have it wrong, This > locks a 10MHz signal to a 1Hz (1pps) signal. What makes it lock to 10 > 000 000Hz instead of 999 999Hz or 10 000 001Hz? Just the hope that the > 10MHz is exactly that? > > Cheers, > Will > > On 26/09/15 08:32, Jim Harman wrote: > > To further demonstrate the Diode - R- C- approach, here (hopefully) is a > > screenshot of the raw DAC output vs time on my Arduino Micro (32u4) based > > system. For this test the oscillator is free running with an error of > about > > 1 usec per 460 sec or 2.17x10^-9. The horizontal scale is 125 sec/div > (1000 > > sec total) and the vertical is 1024 DAC counts (0-2.56 V) which > > corresponds to 1 usec of offset between the oscillator and the reference. > > > > You can see that there is some curvature because the capacitor is being > > charged through a resistor and not a true current source, but as I > > mentioned earlier this does not affect the system's ability to lock the > > oscillator to the pps reference. When locked with a time constant of 1000 > > sec, the phase detector output is almost always less than +/- 100 counts > > from the setpoint of 500. > > > > The noise is due mostly to jitter in my PPS reference, which is generated > > by an Adafruit GPS module. Presumably it would be less if I had a real > > timing receiver. > > > > > > . > > If the inserted image does not come through, I will re-send as an > > attachment. > > > >> -- > > --Jim Harman > > > > > > > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4046 experiment for gpsdo
To further demonstrate the Diode - R- C- approach, here (hopefully) is a screenshot of the raw DAC output vs time on my Arduino Micro (32u4) based system. For this test the oscillator is free running with an error of about 1 usec per 460 sec or 2.17x10^-9. The horizontal scale is 125 sec/div (1000 sec total) and the vertical is 1024 DAC counts (0-2.56 V) which corresponds to 1 usec of offset between the oscillator and the reference. You can see that there is some curvature because the capacitor is being charged through a resistor and not a true current source, but as I mentioned earlier this does not affect the system's ability to lock the oscillator to the pps reference. When locked with a time constant of 1000 sec, the phase detector output is almost always less than +/- 100 counts from the setpoint of 500. The noise is due mostly to jitter in my PPS reference, which is generated by an Adafruit GPS module. Presumably it would be less if I had a real timing receiver. . If the inserted image does not come through, I will re-send as an attachment. > > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 4046 experiment for gpsdo
Hi Can, I suppose your circuit will work as you describe, but the diode-R-C network at the output of the HC4046 followed by an A/D converter works fine if your application is to lock an oscillator to a reference and you don't care if there is a constant time (phase) difference between the two when locked. The key is that instead of trying to reduce the time difference to zero, you define a setpoint near the middle of the range of the phase comparator. You then adjust the frequency of the oscillator to keep the phase comparator output near the setpoint. Using PC3, 1 MHz for the oscillator, and 1 PPS for the reference, you will get a pulse 0-1 usec wide. If you have a 10 bit A/D converter reading the height of the integrated pulse, you get 1 nsec resolution, which is at least 10x better than anything you will get from an all-digital solution counting clock cycles. Defining the setpoint at 500 A/D counts in the filter algorithm will control the oscillator so it is nominally 500 ns ahead of the reference. On Fri, Sep 25, 2015 at 2:18 AM, Can Altineller wrote: > Hello All, > > I got a CD74HC4046 and started to experiment. It seems that this is a newer > version, which has another phase comparator instead of the zener diode. > There has been some changes in the chip basically. PC1out is a xor gate, > and PC3out is an RS flip flop. It will give pulses if one source is behind, > and it will give reverse pulses if one source is forward. PP pin gives the > reverse of every phase differences corresponding to a rising edge, so it is > half the xor pulses in frequency. > > I made the following circuit on breadboard: > > > > 1PPS pulses from both RTC and SYNC source gets inverted, (because we are > interested in falling edges) - Signal and comparator pins of 4046 is fed > with those pulses. The PC1 out is a XOR phase pulses, for both rising and > falling edges, so we are only measuring it for display purposes on the > following images. > > P3Out gives a pulse, if source is behind it will give a sharp pulse from 0 > to logic 1 voltage, and if source is forward it will be at logic 1 voltage, > and give a sharp drop. (On the circuit above the 4046 has no zener, but PC3 > instead). > > The PP output from 4046 inverted gives as the phase pulse, no matter if it > is lacking or forward it will give the same normal pulse. By using and > gates and getting > !PP & PC3Out gives us forward pulse, and !PP && !PC3Out gives us reverse > pulse. > > Here is a logic analyzer capture of XOR, Forward pulse and reverse pulse, > when the RTC is behind. > > > And here Source is behind > > > > So in summary, we get pulses from one pin saying that the RTC is behind, > and if RTC is forward it will pulse from the other pin. I will now proceed > to feed these pulses into the RC network. > > I got this far tru experimentation with the 4046. The VCO can also be > inhibited for low power consumption, (since we are only using the phase > comparators) > I tried a lot of logic circuits to cover a generalized case of the phase > difference between clock pulses, but now I want to make a hybrid algorithm > which will work with interrupts until within certain range steering the > clock in to the zone, and then it might tune from the RC networks. (I would > use two of them, for increasing and decreasing the oscillator) > > I would love to hear your comments for the above circuit because I might > have overlooked something major, that will screw up the operation. > > Best Regards, > Can > > > > ___________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Value of parts for the RC network of "GPSDO with 1ns res TIC"
Diode at HC4046 output pin 15 is 1N5711 (Schottky signal diode) This is in series with 3900 ohm resistor. Cap to ground is 1nf NPO ceramic Resistor across the cap is 1 M These values are suitable for the Arduino Uno (ATmega 328 processor) with the analogReference set to INTERNAL. This gives the ADC a full-scale range of 1.1 V. On the Micro (32u4 processor) the ADC range is 2.56 V so the cap should be 220 pf. Pin 3 of the HC4046 is fed by 1 MHz derived from the oscillator to be controlled and pin 14 is the 1 pps from the GPS, which also drives the interrupt that triggers the ADC. The phase comparator is basically an R-S flip-flop. Once per second it produces a 5 V pulse 0-1 microsec wide. The width of this pulse corresponds to the time difference between the two inputs. When the pulse goes H, the cap starts to charge through the diode and 3900 ohm resistor. The cap stops charging when the pulse goes L. The diode prevents it from being discharged by the LS4046. The ADC is triggered at the end of the pulse, reading the peak value on the cap and thus the time difference. The 1 M resistor discharges the cap over the remainder of the second before the next pulse. The charging slope is not exactly linear, but for 0-1.1V it is pretty close. It is noticeably curved for 0-2.56V, but works fine for this application. It would be quite easy to linearize the response in software. On Wed, Sep 23, 2015 at 7:07 PM, Can Altineller wrote: > Hello, > > I got some 4046 plls and I decided to implement the schematic given on: > > > https://www.febo.com/pipermail/time-nuts/attachments/20140211/8bdbc232/attachment-0004.jpg > > in the drawing phase comparator 3 output is connected to a diode, which > then is fed to a network, and then read from an adc. I see a 1nF capacitor, > but the other 2 parts I can not identify. (I am guessing one is a 1M > resistor, and the other above is some inductor maybe? > > Best regards, > C.A. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Value of parts for the RC network of "GPSDO with 1ns res TIC"
On Thu, Sep 24, 2015 at 10:14 AM, Jim Harman wrote: > The diode prevents it from being discharged by the LS4046. Sorry, I meant HC4046. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] algorithms and hardware for comparing clock pulses
Hi Can, For a simple analog solution, you might try a 74HC4046 phase detector followed by a diode and RC network as used in Lars Walenius' GPSDO, described here in the archives: https://www.febo.com/pipermail/time-nuts/2014-February/082820.html The phase detector produces a pulse whose width equals the time difference between the two pulses. The RC network converts this to a voltage proportional to the time difference, which you then measure with the MCU's A/D converter. Using the rising edge of the signal at pin 14 as the interrupt source triggers the A/D converter at the end of the pulse, which corresponds to the peak of the analog signal.. The 1 meg resistor discharges the capacitor between pulses. Lars' code also includes a filtering algorithm which does a nice job of controlling one of the oscillators to match the 1-PPS generated by the GPS. I have enhanced this if you are interested. On Mon, Sep 21, 2015 at 1:45 PM, Can Altineller wrote: > > >I probably need a hardware to measure the time pulses more precisely. I > thought of XOR'ing the clocks, and measuring both rising and falling edges > trough interrupts, but when the pulse is close enough, it will lead to same > condition. > >Are there any solutions to this problem? Maybe an analog hack? And what > are the mostly used algorithms to tune an oscillator to another? Currently > my algorithm sign corrects the result difference, and adjusts aging > register simply by adding to it, then runs a conversion command each second > to add or substract the ppms. > >This looks a lot of fun, > >Best Regards, >Can Altineller > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] I've designed a GPSDO, but how "good" is it?
On Sun, Aug 16, 2015 at 3:31 PM, Tom Van Baak wrote: > I was hoping someone would someday use a cheap Sparkfun / Parallax / > Adafruit GPS to make a low-cost GPSDO. I have made such a device using the Adafruit module and an Arduino processor. The design is based on the one posted here by Lars Walenius last year. My design constraints were basically: -- no surface mount components that I have to solder myself -- no custom PC boards -- no built-in display, runs stand-alone or with a PC as a monitor My oscillator is a 10 MHz C-Mac STP-2322 from the auction site. Like Nick, I do not have an independent reference to compare it to, but it is set up with a laptop as a monitor so I can plot the TIC output in real time. I have attached a screenshot that shows the TIC variation over 24 hours.This is with a filter time constant of 2048 seconds. The black line at the center is the raw TIC value, sampled every 86 seconds, and the red line is a smoothed version of that. The vertical scale is approx. 100 ns per division (range is 300-700). As you can see, TIC variation is typically about +/- 40 ns. The longer term variations are very repeatable from day to day, probably due to the periodicity of the GPS constellation. I am using Adafruit's external antenna located in my attic with 10m of extra cable. As often observed here, the variation is much worse if I have a poor antenna location. It would probably be better if my antenna was up high and outdoors. The blue line at the bottom is the value being sent to the DAC and the green line at the top is the ambient temperature --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Which First GPSDO to buy?
On Sat, Dec 13, 2014 at 9:36 PM, Bob Camp wrote: > The problem with “build it yourself” is that there is no way do know if > you got it right unless you have something to compare your design to. You > *will* make mistakes as you build one of these…. I think you will have the same problem with an off-the-shelf unit if you don't have at least one reference for comparison. However speaking from experience with Lars Walenius' Arduino-based design, I can say that it is not hard to make a working system, even without another reference. Along the way you will learn a tremendous amount about how these systems work, plus a lot about Arduino programming. Lars' design will run stand-alone, but if you want it can send very useful logging data to a PC, much more informative than a "locked" led on a commercial unit. Total cost including processor, Adafruit GPS shield, and $25.00 ebay OCXO is about $100.00 -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] SMIQ manual
In Gmail, if you hover over the sender's name then click on the envelope icon, the reply goes to the individual. If you click on the reply arrow, it goes to the list. In either case, the recipient is shown at the top of the reply pane. Another gmail trick: if you highlight part of the message then click on the reply arrow (as I did with Paul's message) then in the reply to the group it only quotes the part you have highlighted. Otherwise by default it quotes the whole message, much of which may be hidden by the gray "..." box. On Wed, Dec 10, 2014 at 5:01 PM, paul swed wrote: > Tom > Thanks > What I just realized is I need to check the email address carefully. I > thought the little envelope in gmail was a direct address. I am unsure I > have figured it out correctly yet but will keep an eye out to see if I can > figure out whats up. > Regards > Paul > WB8TSL > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] tcxo
More Arduino clock and timekeeping notes: If the part connected to the processor's XTAL1 and XTAL2 pins has 2 pins and external capacitors it is a crystal. If it has 3 pins and no caps it is a ceramic resonator. If you have a crystal, you can fine-tune its frequency by replacing one of the capacitors with a variable cap. You may have trouble using an external oscillator instead of whatever is there because the chip is supposed to be set up differently when you do that. See Sec. 9 of the ATMega datasheet for further info. Another and potentially more flexible approach (again depending on your requirements) would be to leave the processor clock alone and connect an accurate external oscillator to a timer input. Then you can use timer interrupts and/or the timer capture function for precise timekeeping. On Thu, Dec 11, 2014 at 9:31 AM, folkert wrote: > > Some of the Arduinos (not sure about Mini 04 but I am suspicious) use > > ceramic resonators rather than real crystals and thus may have extremely > > poor frequency stability. See here > > http://jorisvr.nl/arduino_frequency.html > > for an example. > > ah! > Very intriguing material, those crystals. I wonder what happens in them > that they start to tick(?) at precisely 16MHz for example. > > > Is there some reason you are using a 16.9344 MHz oscillator rather than > > 16.0? The processor will probably work, but timing of Arduino functions > > like millis() and software serial baud rates will be affected. > > Misread I guess :-| > Like that time that I bought 20 max690 instead of max680 ics. sigh. > > > On Wed, Dec 10, 2014 at 2:19 PM, folkert wrote: > > > > > > I'm experimenting a bit with time keeping. > > > > For that I use cheap low power hardware like raspberry pies and > > > > arduinos. > > > > > > Hi people, > > > > > > Thanks for all the replies! Took a bit to respond but I had the flu. > > > > > > My objective is, to get the best precision/accuracy possible with said > > > hardware. > > > > > > The first step is preparing an arduino. I found one that has an easy to > > > desolder crystal: > > > > > > > http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Arduino_Mini.jpg/170px-Arduino_Mini.jpg > > > Bought a couple of those and some of these: > > > > > > > http://www.aliexpress.com/item/Precision-TCXO-square-wave-oscillator-TCXO-16-9344MHz-line-rectangle/1104200137.html > > > > > > While waiting for these and the parts for the schematics, I'm toying > > > around with implementing ntp servers (well, sntp) for arduino. With > > > lots of blinkenlights of course and with ethernet. Not trivial I can > > > say. > > > This is the jitter plot of a test where time is fed from an RTC module. > > > I did not plot the drift but it is +/- 120 seconds in the 3.8 days I > > > measured it. > > > http://vps001.vanheusden.com/~folkert/aRTC.png > > > > > > > > > Folkert van Heusden > > > > > > -- > > > -- > > > Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com > > > ___ > > > time-nuts mailing list -- time-nuts@febo.com > > > To unsubscribe, go to > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > > > -- > > > > --Jim Harman > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > Folkert van Heusden > > -- > Multitail est un outil permettant la visualisation de fichiers de > journalisation et/ou le suivi de l'exécution de commandes. Filtrage, > mise en couleur de mot-clé, fusions, visualisation de différences > (diff-view), etc. http://www.vanheusden.com/multitail/ > -- > Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] tcxo
Some of the Arduinos (not sure about Mini 04 but I am suspicious) use ceramic resonators rather than real crystals and thus may have extremely poor frequency stability. See here http://jorisvr.nl/arduino_frequency.html for an example. Is there some reason you are using a 16.9344 MHz oscillator rather than 16.0? The processor will probably work, but timing of Arduino functions like millis() and software serial baud rates will be affected. On Wed, Dec 10, 2014 at 2:19 PM, folkert wrote: > > I'm experimenting a bit with time keeping. > > For that I use cheap low power hardware like raspberry pies and > > arduinos. > > Hi people, > > Thanks for all the replies! Took a bit to respond but I had the flu. > > My objective is, to get the best precision/accuracy possible with said > hardware. > > The first step is preparing an arduino. I found one that has an easy to > desolder crystal: > > http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Arduino_Mini.jpg/170px-Arduino_Mini.jpg > Bought a couple of those and some of these: > > http://www.aliexpress.com/item/Precision-TCXO-square-wave-oscillator-TCXO-16-9344MHz-line-rectangle/1104200137.html > > While waiting for these and the parts for the schematics, I'm toying > around with implementing ntp servers (well, sntp) for arduino. With > lots of blinkenlights of course and with ethernet. Not trivial I can > say. > This is the jitter plot of a test where time is fed from an RTC module. > I did not plot the drift but it is +/- 120 seconds in the 3.8 days I > measured it. > http://vps001.vanheusden.com/~folkert/aRTC.png > > > Folkert van Heusden > > -- > -- > Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lightening protection of a GPSDO system / optical isolated distribution amp
The topic has shifted from lightning protection, but I thought I would share my experiences on diurnal timing shifts. On my home-built GPSDO, similar to the design posted by Lars Walenius some time ago, I can see variations in the TIC output that correlate well to to the variations 24 hours ago. The variations are about 100 ns p-p and are noticeably larger when it is raining outside. I think the variations were also greater over the summer, when the sky view was more obstructed by leaves. My system uses an Adafruit (Globaltop) GPS module, so not the greatest for timing applications. I have an outdoor puck antenna located a few feet above ground level and a few feet from a wooden house, with a mostly unobstructed view to the west. The time constant for steering the OCXO is set to 2048 sec. The timing variations appear as noisy "lumps" that last about 90 minutes, so the disciplining is reducing but not eliminating the variations. On Sun, Dec 7, 2014 at 2:49 PM, Bob Camp wrote: > Hi > > The 12 hour periodicity of GPS is (in general) less obvious in an ADEV > plot than 24 and 48 hour effects. Part of this is due to the lower “floor” > at longer tau. Another part of it is due to things like the ionosphere > being at different places at the 12 hour points. > > Bob > > > On Dec 7, 2014, at 2:27 PM, Chris Albertson > wrote: > > > >> > >> Bob, > >> can you explain more about the effect of antenna performance on a GPSDO > >> system? > >> > >> Now you have told me it is important, I would like to know more! My lab > >> has an East facing window. > > > > > > Physically what is happening here is that the error bars on the fix your > > GPS gets will cycle over a 12 hour period because of the sats all have > 12 > > hour orbital periods. If you can only see part of the sky the amplitude > > of this is greater. > > > > As an example thing of the worst possible case where you antenna can only > > see a few degrees of the sky. Every 12 hours one GPS satellite comes > into > > view and your GPS gets a decent "fix" but then for 8 hours the GPS sees > > nothing and drifts off. Now think about moving the antenna to a > marginally > > better place where it always sees at last ONE GPS stiletto but for 8 > hours > > there are two and for 2hours there are three satellites. The quality if > > the "fix" would still vary but would be better. In the best case your > 12 > > channel GPS receiver ALWAYS is able to select the 12 BEST places GPS > > satellites that are in view. > > > > This is not a great effect as long as there is enough sky that there are > > always some in view. > > > > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] tcxo
Folkert, You don't make your detailed requirements clear, but you might be interested in this module http://www.adafruit.com/product/255 It uses a DS3231 chip, which is a 32.768 khz oscillator with built-in temperature sensing. Based on the temperature, it automatically switches in internal capacitors to adjust the frequency. You can access and control it with an Arduino library, including adjusting the nominal frequency with software. Accuracy is not up to time-nuts standards, but will be much better than an Arduino crystal may be adequate for your application. Disclosure: I have no connection with the manufacturer or distributor, but I did experiment with one of these before descending further into time-nuttery. On Sun, Dec 7, 2014 at 3:53 PM, folkert wrote: > Hi, > > I'm experimenting a bit with time keeping. > For that I use cheap low power hardware like raspberry pies and > arduinos. > I noticed that the accuracy of a crystal makes a big difference. Did a > bit of googling and I learned that a txco may help solve that. > Something that keeps a constant temperature that is that I can then > glue/solder to the crystal of those systems. > My question now is: does anyone know of a simple schema for such a > thing? > I'm not entirely new to soldering but large schemas with lots of > components are a bit daunting as I don't have the background knowledge > to debug them if I soldered something wrong. > > > Folkert van Heusden > > -- > MultiTail är ett flexibel redskap för att följa en eller flera logfiler, > utföra > kommandon, filtrera, färglägga, sammanfoga, o.s.v... > -- > Phone: +31-6-41278122, PGP-key: 1F28D8AE, www.vanheusden.com > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Correcting jitter on the1 PPSsignalfromaGPSreceiver.
> > > Another problem with unterminated lines is that if the ringing is bad enough, you may clock something or interrupt twice, with unpredictable results. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Effects of noise on EFC line?
I was able to quiet things down a lot by putting a 100 ohm resistor in series with the 74HC output. If these guys drive more than a few inches of wire, they ring like crazy. Also make sure you pay close attention to the bypassing of the 5V supply. Make your bypass cap lead lengths as short as possible. On Tue, Aug 5, 2014 at 2:36 PM, Bob Stewart wrote: > I've run into a noise problem on the EFC line of my GPSDO engine at the > frequency of the oscillator. I've traced the source down to the 74HCT365 > I'm using to output the 1(or 5)MHz and 10MHz signals. When I pull it, the > EFC quietens down a lot. I'm seeing about 50mv of 10MHz noise at the > output of the op-amp that feeds the EFC voltage divider at the OCXO. The > voltage divider is corrected by the VRef from the OCXO with a simple > circuit using temp-co'ed resistors. On the 0.1uf cap at the OCXO's EFC > pin, I'm seeing about 5mv of 10MHz signal. > > > I've considered switching the HCT out for a 74LS365, assuming my drive > levels are compatible. Unfortunately, I don't have one "in stock", and > "I'm way out of my pay grade", as they say. I've also thought about > putting a 100uh inductor in series with the EFC line. I wonder if I'll > have to isolate the 74xx365 chip's VCC through an inductor? Any thoughts? > > > I'm also wondering what the impact of this level of on-frequency noise > will be? Is the impact somewhat mitigated, since it's at oscillator > frequency? I don't have anything better than an HP 8558B to look at the > output of the board. > > I'm not quite ready to generally share my schematic with the list, but I > can make individual exceptions. > > > Bob - AE6RV > _______ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] New timing receivers?
On Mon, Apr 28, 2014 at 1:08 AM, Mark Sims wrote: > When I was playing with an Adafruit GPS, it appeared that if it thought > you were not moving it would go into a pseudo-position-hold mode and the > output coords would not change. It took it a while to start outputting new > coords when you started moving again. This test was at walking speeds. I > had to walk maybe 100 feet before it started sending new coords. The 3339 chip has a command PMTK386 to set its "Nav Speed Threshold." This is intended to prevent the position from drifting if the unit is stationary. You can also query the current setting with the PMTK447 command, and it should respond with a PMTK527. For details you can download the document " GlobalTop PMTK command packet." There are several versions available on the web, the newest I was able to find is A11, at http://doxical.free.fr/resources/exstatic/PA6B_Flash/PMTK%20command%20packet-Complete-A11.pdf Note that the document version linked form the Adafruit website is not the newest, and that for some reason the 3318 and 3329 use a different command for this function. I believe the default setting for this option is a firmware option, so units may have different settings at power-up. My unit also seems to wander around, but I have not experimented to see if its location changes correspond to timing changes, or if changing the nav speed threshold affects the timing accuracy. BTW I have not seen the dropped PPS signals some have reported. I am using the Adafruit antenna outdoors, with a view of about half the sky, looking east. -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Frequency of LC Tank.
First order approximation of course would be to sweep the frequency and look for a dip (peak for series resonant) in the DC current drawn by the driver. On Fri, Apr 11, 2014 at 4:15 PM, Dan Kemppainen wrote: > when actively driving a tank circuit, how do you > know you are driving it with the same frequency ad the same phase it > naturally oscillates at > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Adafruit (MT3339) problems today
On Thu, Apr 10, 2014 at 6:46 PM, Bob Stewart wrote:
> Could you give me a bit more information on using WAAS?
I used the Adafruit library to send it the message
// Turn on WAAS
GPS.sendCommand("$PMTK301,2*2E");
and after that the GGA message shows a fix type of 2 where it previously
showed type 1. To see what mode it is in you can send it the PMTK401
message and it should respond with a PMTK501,2 if WAAS is enabled and
PMTK501,0 if not.
I believe this setting persists after power-down as long as you have a
backup battery installed and don't do a full reset.
WAAS only works in North America. I don't know details elsewhere, but the
PMTK313 message says it turns searching for SBAS satellites on and off.
--
--Jim Harman
___
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Re: [time-nuts] Yet another Arduino-based GPSDO
I have not tried the dual PWM-based DAC, but my concern is that depending on the ratio of the resistors it might not be monotonic as the output goes from say 0FF to 100 hex. You would see this problem in the output every 256 counts. Unless there is significant dither in the DAC values, this could cause the system to get stuck as it tries to track a slow change in the oscillator. The nominal resistor ratio is 255:1. I think it would be best to choose the resistors (including tolerance) so that the big one is sure to be more than 255x the smaller one. This would cause a jump rather than a kink in the output as the DAC varies. Lars uses 39k and 10 megs, which does not quite meet this criterion. On the integrator, I am using Lars' circuit with a TDK C0G ceramic capacitor FK28C0G1H102J, which is supposed to be good to 30ppm/deg C, and no-name carbon resistors. I will fiddle with it and see if I can figure out where the sensitivity is coming from. On Wed, Apr 9, 2014 at 10:20 PM, Chris Albertson wrote: > But the cheap 16-bit Lars used is > working very well. PWM works because we only need less then 1Hz > bandwidth so we can filter the heck out of it.The steps are less > than I can measure > > What TIC capacitor did you use. If it is that temperer sensitive you > might want to replace it. > -- --Jim Harman ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
