Re: [time-nuts] Win XP and NIST time
The appearent conflict here is in the definition of "real time". For the video capture application we only need to keep up with the average data rate and if the system stops reading data for a few tens of milliseconds and lets it buffer in the capture hardware then it is OK because nothing is lost. The only criteria for success is "nothing is lost". The SDR application is a little more time critical because it needs to play the proceed audio. But again it can be buffered and we'd never notice a 50 millisecond lag in audio and for radio a 100 ms lag might go unnoticed But there is a category of what engineers ca "hard real time". Home computer users don't normally use their PCs for hard real time applications. This would be things like controlling a walking robot, guiding an anti aircraft missile or just about any time a computer is inside the feedback loop of a control system. These are all engineering and science applications that home users wouldn't see. A "harder" real time use that people DO see in home use is music. If you try to do multi-track recording in a home music studio with windows. This can be done but people have to do thinks like (1) remove everything non music related from the PC and disconnect it from the network. (2) replace the audio subsystem software with special real-time ASIO audio drivers. Then it can work So ""real-time" has a wide range of meanings, video capture is about the easiest to do and being embedded in a servo control loop the hardest On Tue, Mar 26, 2013 at 6:08 PM, David I. Emery wrote: > On Tue, Mar 26, 2013 at 07:39:51PM +0100, Alberto di Bene wrote: >> On 3/26/2013 7:21 PM, Dan Kemppainen wrote: >> >> >Keep in mind, we are after all, taking about windows. An operating >> >system that IS NOT real time operating system. (You think it is, try >> >move a continuous stream of a few 6+ MBytes/Sec data to it!) >> >> Well, the Perseus SDR, when set to its maximum sampling rate after the DDC, >> sends >> the I and Q continuous streams (24 bit/sample each), to the PC at a rate of >> 2 MHz. This >> means 12 MBytes/sec via a high speed USB2 port. Using one the many >> available SDR >> programs, those 12 MBytes/sec are received, FIR and FFT are applied, >> demodulation >> algorithms are used, and there are no glitches in the final audio... if >> even a single sample >> would be lost, you would ear immediately the artifact >> >> Windows is not as bad as somebody would depict it... :-) > > I have been using Windows for digital video analysis and > capture for years... often capture multiple 70-80 mb/s transport streams > by the hour from USB and PCI sources and output similar for testing. > > It works. > > Does take buffering and tuning in the code, and some in the > hardware. > > > > -- > Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass > 02493 > "An empty zombie mind with a forlorn barely readable weatherbeaten > 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in > celebration of what could have been, but wasn't and is not to be now either." > > ___ > 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 ___ 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] Win XP and NIST time
SDR isn't as taxing as you think. I'm running 4 of those rtlsdr type dongles on an A8-cortex. Granted under linux, but this is a single core Arm. The "multimedia" versions of linux don't get much press these days since the kernel itself now is rather low latency. But if you google "linux musicians" or "windows musicians", there are tips for latency reduction. One of the nicest things you can do to a computer is turn off the stupid file indexing. On windows, the program "everything" is faster than windows file search ever was, and doesn't need the index. -Original Message- From: Chris Albertson Sender: time-nuts-boun...@febo.com Date: Wed, 27 Mar 2013 08:38:32 To: Discussion of precise time and frequency measurement Reply-To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Win XP and NIST time The appearent conflict here is in the definition of "real time". For the video capture application we only need to keep up with the average data rate and if the system stops reading data for a few tens of milliseconds and lets it buffer in the capture hardware then it is OK because nothing is lost. The only criteria for success is "nothing is lost". The SDR application is a little more time critical because it needs to play the proceed audio. But again it can be buffered and we'd never notice a 50 millisecond lag in audio and for radio a 100 ms lag might go unnoticed But there is a category of what engineers ca "hard real time". Home computer users don't normally use their PCs for hard real time applications. This would be things like controlling a walking robot, guiding an anti aircraft missile or just about any time a computer is inside the feedback loop of a control system. These are all engineering and science applications that home users wouldn't see. A "harder" real time use that people DO see in home use is music. If you try to do multi-track recording in a home music studio with windows. This can be done but people have to do thinks like (1) remove everything non music related from the PC and disconnect it from the network. (2) replace the audio subsystem software with special real-time ASIO audio drivers. Then it can work So ""real-time" has a wide range of meanings, video capture is about the easiest to do and being embedded in a servo control loop the hardest On Tue, Mar 26, 2013 at 6:08 PM, David I. Emery wrote: > On Tue, Mar 26, 2013 at 07:39:51PM +0100, Alberto di Bene wrote: >> On 3/26/2013 7:21 PM, Dan Kemppainen wrote: >> >> >Keep in mind, we are after all, taking about windows. An operating >> >system that IS NOT real time operating system. (You think it is, try >> >move a continuous stream of a few 6+ MBytes/Sec data to it!) >> >> Well, the Perseus SDR, when set to its maximum sampling rate after the DDC, >> sends >> the I and Q continuous streams (24 bit/sample each), to the PC at a rate of >> 2 MHz. This >> means 12 MBytes/sec via a high speed USB2 port. Using one the many >> available SDR >> programs, those 12 MBytes/sec are received, FIR and FFT are applied, >> demodulation >> algorithms are used, and there are no glitches in the final audio... if >> even a single sample >> would be lost, you would ear immediately the artifact >> >> Windows is not as bad as somebody would depict it... :-) > > I have been using Windows for digital video analysis and > capture for years... often capture multiple 70-80 mb/s transport streams > by the hour from USB and PCI sources and output similar for testing. > > It works. > > Does take buffering and tuning in the code, and some in the > hardware. > > > > -- > Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass > 02493 > "An empty zombie mind with a forlorn barely readable weatherbeaten > 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in > celebration of what could have been, but wasn't and is not to be now either." > > ___ > 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 ___ 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] Win XP and NIST time
albertson.ch...@gmail.com said: > For the video capture application we only need to keep up with the average > data rate and if the system stops reading data for a few tens of > milliseconds and lets it buffer in the capture hardware then it is OK > because nothing is lost. The only criteria for success is "nothing is > lost". I agree in general. The catch is that you need enough buffering. In lots of cases, buffering is expensive so the hardware designers try to avoid it. A big chunk of the USB architecture is trying to guarantee service so the dongle designer can figure out how little buffering they can get away with. -- 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.
Re: [time-nuts] Win XP and NIST time
Good explanation. I guessed, since the list is "time nuts" I assumed "real time" in reference to an OS would be understood. :) My bad. Because windows is not a real time operating system (RTOS), I lack seeing the purpose in getting the windows clock synchronized to within microseconds or nanoseconds of anything. Even if you could do it, you won't get much out of doing so. I've seen windows regularly stall critical code loops for more than a second at a time, when the loops would normally take a few milliseconds to run. If reading data down a USB connection, with limited buffering on the USB peripheral, data can and will be lost in streaming applications. (I suspect the SDR mentioned has a good bit of buffering in it!) As for timing things on windows, check out how to read the performance counters in windows. I believe these are QueryPerformanceCounter and QueryPerformanceFrequency in kernel32. In most modern systems these should give a time stamp from the system start, at the native core clock frequency. Now, using these with interrupts on some sort of input, one should be able to get some really good resolution on measurements from a PC. If the CPU clock frequency was locked to a really good source, you could get quite a system out of it... Dan On 3/27/2013 12:00 PM, time-nuts-requ...@febo.com wrote: The appearent conflict here is in the definition of "real time". For the video capture application we only need to keep up with the average data rate and if the system stops reading data for a few tens of milliseconds and lets it buffer in the capture hardware then it is OK because nothing is lost. The only criteria for success is "nothing is lost". The SDR application is a little more time critical because it needs to play the proceed audio. But again it can be buffered and we'd never notice a 50 millisecond lag in audio and for radio a 100 ms lag might go unnoticed But there is a category of what engineers ca "hard real time". Home computer users don't normally use their PCs for hard real time applications. This would be things like controlling a walking robot, guiding an anti aircraft missile or just about any time a computer is inside the feedback loop of a control system. These are all engineering and science applications that home users wouldn't see. A "harder" real time use that people DO see in home use is music. If you try to do multi-track recording in a home music studio with windows. This can be done but people have to do thinks like (1) remove everything non music related from the PC and disconnect it from the network. (2) replace the audio subsystem software with special real-time ASIO audio drivers. Then it can work So ""real-time" has a wide range of meanings, video capture is about the easiest to do and being embedded in a servo control loop the hardest ___ 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] Win XP and NIST time
The timing/logging of events can benefit from precise time, even if the processing of such data is not real time. MLAT/TDOA for example. But I believe stock trading uses precise timing in order to queue orders. On my list of sdr hacks is a radio interferometer. Precise event timing there would be key. (I will have to hack the sdrs to use one time source.) -Original Message- From: Dan Kemppainen Sender: time-nuts-boun...@febo.com Date: Wed, 27 Mar 2013 12:46:08 To: Reply-To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Win XP and NIST time Good explanation. I guessed, since the list is "time nuts" I assumed "real time" in reference to an OS would be understood. :) My bad. Because windows is not a real time operating system (RTOS), I lack seeing the purpose in getting the windows clock synchronized to within microseconds or nanoseconds of anything. Even if you could do it, you won't get much out of doing so. I've seen windows regularly stall critical code loops for more than a second at a time, when the loops would normally take a few milliseconds to run. If reading data down a USB connection, with limited buffering on the USB peripheral, data can and will be lost in streaming applications. (I suspect the SDR mentioned has a good bit of buffering in it!) As for timing things on windows, check out how to read the performance counters in windows. I believe these are QueryPerformanceCounter and QueryPerformanceFrequency in kernel32. In most modern systems these should give a time stamp from the system start, at the native core clock frequency. Now, using these with interrupts on some sort of input, one should be able to get some really good resolution on measurements from a PC. If the CPU clock frequency was locked to a really good source, you could get quite a system out of it... Dan On 3/27/2013 12:00 PM, time-nuts-requ...@febo.com wrote: > The appearent conflict here is in the definition of "real time". > > For the video capture application we only need to keep up with the > average data rate and if the system stops reading data for a few tens > of milliseconds and lets it buffer in the capture hardware then it is > OK because nothing is lost. The only criteria for success is > "nothing is lost". > > The SDR application is a little more time critical because it needs to > play the proceed audio. But again it can be buffered and we'd never > notice a 50 millisecond lag in audio and for radio a 100 ms lag might > go unnoticed > > But there is a category of what engineers ca "hard real time". Home > computer users don't normally use their PCs for hard real time > applications. This would be things like controlling a walking robot, > guiding an anti aircraft missile or just about any time a computer is > inside the feedback loop of a control system. These are all > engineering and science applications that home users wouldn't see. > > > A "harder" real time use that people DO see in home use is music. If > you try to do multi-track recording in a home music studio with > windows. This can be done but people have to do thinks like (1) > remove everything non music related from the PC and disconnect it from > the network. (2) replace the audio subsystem software with special > real-time ASIO audio drivers. Then it can work > > So ""real-time" has a wide range of meanings, video capture is about > the easiest to do and being embedded in a servo control loop the > hardest ___ 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] Win XP and NIST time
On Wed, Mar 27, 2013 at 9:46 AM, Dan Kemppainen wrote: > > As for timing things on windows, check out how to read the performance > counters in windows. I believe these are QueryPerformanceCounter and > QueryPerformanceFrequency in kernel32. In most modern systems these should > give a time stamp from the system start, at the native core clock frequency. > If you use those, you have to lock the thread you are timing to one CPU/Core as the performance counters are per CPU/Core and can get out of step. Or you can force your thread onto one CPU for the QueryPerformanceCounter call. This seems to be a bad idea to me as it would add an indeterminate time before querying the counter (indeterminate as if you are running on a different CPU, the OS would have to switch to the one you requested). Search for SetThreadAffinityMask and/or SetProcessAffinityMask along with QueryPerformanceCounter. Then all bets are off if you have a CPU that runs at variable speed if you want the result to be actual time. Orin. ___ 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] Win XP and NIST time
orin.e...@gmail.com said: > Then all bets are off if you have a CPU that runs at variable speed if you > want the result to be actual time. I think that got fixed on newer CPU chips. I don't know when. Another interesting problem in that area is that the temperature changes with the CPU load. The crystal on most PCs actually makes a pretty good thermometer. -- 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.
Re: [time-nuts] Win XP and NIST time
On 3/27/2013 2:54 PM, time-nuts-requ...@febo.com wrote: Then all bets are off if you have a CPU that runs at variable speed if you >want the result to be actual time. I think that got fixed on newer CPU chips. I don't know when. Another interesting problem in that area is that the temperature changes with the CPU load. The crystal on most PCs actually makes a pretty good thermometer. My modern processors (Phenom II x4's etc) don't have this issue with the performance counters. I believe that has been sorted out for a while now. (Thus my qualification of 'should' give you a time stamp from system start). I wouldn't use the performance counters in any critical code, just for testing said code loops while writing them. As for affinity, I do lock my time critical loops in windows to a single core before starting them. Windows is terrible at time critical data streaming stuff when handing off threads from one core to another. You can see the problems pop up as soon as the CPU load shifts from one core to another. And, don't get me started about hyperthreading! :) The bottom line is that windows is not good at doing anything in a timely manner. (Thus the use of lots of buffering!) It was never was meant to run time critical applications, and probably never will. So, knowing what we do about windows, why worry about locking it to anything? Even if the core and RTC were locked to a GPSDO, what will you gain? Correct time of day within a few seconds is good enough for me! Dan ___ 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] OT - DC-10 gyros
Well, I can come up with something topical, read on. :) I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had to buy it. What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that was stripped for parts around 2000. The gyro included the pull tag with tail number, the license number of the A&P mechanic that pulled it, and some other cool stuff. What it turned out to really be is two gyros with two sets of electronics in one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown system. The actual gyro wheel is about the size of your thumbnail. I've just started tracing things out, and I've gotten the gyros to spin up. I really love mechanical gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have great fun getting the package traced out and running. So, to be a bit more topical, the package of course needs 28V 400Hz for the gyros, 28VDC for something, and +/-15V for most of the electronics. Question - anyone figured out some clever solution for the 400Hz power? I faked it with a signal generator and power amp, but that's a bit bulky. I'm thinking I'll use one of the class-D amp ICs and a simple op-amp phase-shift sine generator. Topical in a more abstract way, strapdown systems really are very interesting. They require precise integration of the rate output over time to derive velocity and position, and really weren't practical until the 70's when small enough computers existed to do the requisite calculations. (I worked on the nav system for the Trident missile back in my Draper Labs days). -- Bill Ezell They said 'Windows or better' so I used Linux. ___ 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] OT - DC-10 gyros
How about one of those 2kw car stereo amps with a 555 input tone ? --- On Wed, 3/27/13, Bill Ezell wrote: From: Bill Ezell Subject: [time-nuts] OT - DC-10 gyros To: time-nuts@febo.com Date: Wednesday, March 27, 2013, 1:40 PM Well, I can come up with something topical, read on. :) I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had to buy it. What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that was stripped for parts around 2000. The gyro included the pull tag with tail number, the license number of the A&P mechanic that pulled it, and some other cool stuff. What it turned out to really be is two gyros with two sets of electronics in one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown system. The actual gyro wheel is about the size of your thumbnail. I've just started tracing things out, and I've gotten the gyros to spin up. I really love mechanical gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have great fun getting the package traced out and running. So, to be a bit more topical, the package of course needs 28V 400Hz for the gyros, 28VDC for something, and +/-15V for most of the electronics. Question - anyone figured out some clever solution for the 400Hz power? I faked it with a signal generator and power amp, but that's a bit bulky. I'm thinking I'll use one of the class-D amp ICs and a simple op-amp phase-shift sine generator. Topical in a more abstract way, strapdown systems really are very interesting. They require precise integration of the rate output over time to derive velocity and position, and really weren't practical until the 70's when small enough computers existed to do the requisite calculations. (I worked on the nav system for the Trident missile back in my Draper Labs days). -- Bill Ezell They said 'Windows or better' so I used Linux. ___ 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] OT - DC-10 gyros
Watch eBay for a small static inverter. I got an Abbott one for under $50. It takes 28 VDC and puts out 115VAC 400 Hz. -John === > How about one of those 2kw car stereo amps with a 555 input tone ? > > --- On Wed, 3/27/13, Bill Ezell wrote: > > > From: Bill Ezell > Subject: [time-nuts] OT - DC-10 gyros > To: time-nuts@febo.com > Date: Wednesday, March 27, 2013, 1:40 PM > > > Well, I can come up with something topical, read on. :) > > I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, > I had to buy it. > > What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 > that was stripped for parts around 2000. The gyro included the pull tag > with tail number, the license number of the A&P mechanic that pulled it, > and some other cool stuff. > > What it turned out to really be is two gyros with two sets of electronics > in one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, > it's a strapdown system. The actual gyro wheel is about the size of your > thumbnail. I've just started tracing things out, and I've gotten the gyros > to spin up. I really love mechanical gyros for some reason, too bad > there's not a gyro-nuts group. I'm going to have great fun getting the > package traced out and running. > > So, to be a bit more topical, the package of course needs 28V 400Hz for > the gyros, 28VDC for something, and +/-15V for most of the electronics. > > Question - anyone figured out some clever solution for the 400Hz power? I > faked it with a signal generator and power amp, but that's a bit bulky. > I'm thinking I'll use one of the class-D amp ICs and a simple op-amp > phase-shift sine generator. > > Topical in a more abstract way, strapdown systems really are very > interesting. They require precise integration of the rate output over time > to derive velocity and position, and really weren't practical until the > 70's when small enough computers existed to do the requisite > calculations. (I worked on the nav system for the Trident missile back in > my Draper Labs days). > > -- Bill Ezell > > They said 'Windows or better' > so I used Linux. > > ___ > 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] OT - DC-10 gyros
Great to know there's someone around who loves complex electro-mechanical systems! I thought the population had dropped to zero! Regards, Lee - Original Message - From: "Bill Ezell" To: Sent: Wednesday, March 27, 2013 2:40 PM Subject: [time-nuts] OT - DC-10 gyros Well, I can come up with something topical, read on. :) I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had to buy it. What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that was stripped for parts around 2000. The gyro included the pull tag with tail number, the license number of the A&P mechanic that pulled it, and some other cool stuff. What it turned out to really be is two gyros with two sets of electronics in one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown system. The actual gyro wheel is about the size of your thumbnail. I've just started tracing things out, and I've gotten the gyros to spin up. I really love mechanical gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have great fun getting the package traced out and 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.
Re: [time-nuts] OT - DC-10 gyros
For "thumbsized" gyros, the power-drain is probably very slight. A class-D may or may not be a good idea, I'd worry about the stability faced with a "weird" load like motors. That said, I have been toturing one of these to no end, and not managed to kill it yet: http://classdaudio.com/amplifier-modules/ti-300-amplifier.html Depending on the actual power-requirement, you can also consider the NatSemi audio chips, for instance the LM3875 "gainclone". It is basically a very good high-power op-amp. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] OT - DC-10 gyros
Hi The first question is "how much 400 Hz power do I need?". Without knowing if it's tens of amps (no, it's not…) or a tenth of an amp, it's a bit though to decide how much to spend on the solution. Eight ohms at 28 volts would be just a bit under 4 amps. It's also right at 100 watts. I'd be very surprised it you need anywhere near that much current. You probably want a pure sine wave to keep everything happy. A lot of the simple inverters are "sort of" sine waves. I think I'd vote for something like an cheap audio amp driven by a nice clean / stable 400 Hz tone. Bob On Mar 27, 2013, at 4:40 PM, Bill Ezell wrote: > Well, I can come up with something topical, read on. :) > > I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I > had to buy it. > > What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that > was stripped for parts around 2000. The gyro included the pull tag with tail > number, the license number of the A&P mechanic that pulled it, and some other > cool stuff. > > What it turned out to really be is two gyros with two sets of electronics in > one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a > strapdown system. The actual gyro wheel is about the size of your thumbnail. > I've just started tracing things out, and I've gotten the gyros to spin up. I > really love mechanical gyros for some reason, too bad there's not a gyro-nuts > group. I'm going to have great fun getting the package traced out and running. > > So, to be a bit more topical, the package of course needs 28V 400Hz for the > gyros, 28VDC for something, and +/-15V for most of the electronics. > > Question - anyone figured out some clever solution for the 400Hz power? I > faked it with a signal generator and power amp, but that's a bit bulky. I'm > thinking I'll use one of the class-D amp ICs and a simple op-amp phase-shift > sine generator. > > Topical in a more abstract way, strapdown systems really are very > interesting. They require precise integration of the rate output over time to > derive velocity and position, and really weren't practical until the 70's > when small enough computers existed to do the requisite calculations. (I > worked on the nav system for the Trident missile back in my Draper Labs days). > > -- > Bill Ezell > > They said 'Windows or better' > so I used Linux. > > ___ > 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] OT - DC-10 gyros
Good points, Bob. At 400 Hz and low power, I'd think a decent LC low-pass filter would be feasible for cleaning up any trash on the inverter output. LC to minimize the series losses and provide a bit of peaking at 400 Hz. Tom Holmes, N8ZM Tipp City, OH EM79 > -Original Message- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of Bob Camp > Sent: Wednesday, March 27, 2013 6:21 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] OT - DC-10 gyros > > Hi > > The first question is "how much 400 Hz power do I need?". Without knowing if it's > tens of amps (no, it's not.) or a tenth of an amp, it's a bit though to decide how > much to spend on the solution. > > Eight ohms at 28 volts would be just a bit under 4 amps. It's also right at 100 > watts. I'd be very surprised it you need anywhere near that much current. You > probably want a pure sine wave to keep everything happy. A lot of the simple > inverters are "sort of" sine waves. I think I'd vote for something like an cheap > audio amp driven by a nice clean / stable 400 Hz tone. > > Bob > > On Mar 27, 2013, at 4:40 PM, Bill Ezell wrote: > > > Well, I can come up with something topical, read on. :) > > > > I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had > to buy it. > > > > What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that > was stripped for parts around 2000. The gyro included the pull tag with tail > number, the license number of the A&P mechanic that pulled it, and some other > cool stuff. > > > > What it turned out to really be is two gyros with two sets of electronics in one > box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown > system. The actual gyro wheel is about the size of your thumbnail. I've just started > tracing things out, and I've gotten the gyros to spin up. I really love mechanical > gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have > great fun getting the package traced out and running. > > > > So, to be a bit more topical, the package of course needs 28V 400Hz for the > gyros, 28VDC for something, and +/-15V for most of the electronics. > > > > Question - anyone figured out some clever solution for the 400Hz power? I > faked it with a signal generator and power amp, but that's a bit bulky. I'm thinking > I'll use one of the class-D amp ICs and a simple op-amp phase-shift sine > generator. > > > > Topical in a more abstract way, strapdown systems really are very interesting. > They require precise integration of the rate output over time to derive velocity and > position, and really weren't practical until the 70's when small enough computers > existed to do the requisite calculations. (I worked on the nav system for the > Trident missile back in my Draper Labs days). > > > > -- > > Bill Ezell > > > > They said 'Windows or better' > > so I used Linux. > > > > ___ > > 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] OT - DC-10 gyros
I neglected to mention that. The DC resistance of the motor windings is roughly 200 ohms. I estimate the power draw is < 2 watts. Haven't measured the inductance. I probably could just use some FETs and build a simple class-B amp. The sine wave doesn't have to be absolutely pure. Frequency stability (at least, in a real application) is more important, since the gyro response depends upon the rotational speed of the wheel. Not that I'm going to actually use it for anything other than just getting it working. :) On 03/27/2013 6:21 PM, time-nuts-requ...@febo.com wrote: For "thumbsized" gyros, the power-drain is probably very slight. -- Bill Ezell They said 'Windows or better' so I used Linux. ___ 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] OT - DC-10 gyros
Yeah I'd join a gyro-nuts group. I have a shelf full of weird gyros, a stable platform, other gyro stuff. I made a little power supply to make 28 volts 3 phase 400 Hz, found it in an app note, for running a set of three tiny rate gyros I picked up. I'll go dig it out and let you know. Peter On 3/27/2013 4:40 PM, Bill Ezell wrote: Well, I can come up with something topical, read on. :) I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had to buy it. What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that was stripped for parts around 2000. The gyro included the pull tag with tail number, the license number of the A&P mechanic that pulled it, and some other cool stuff. What it turned out to really be is two gyros with two sets of electronics in one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown system. The actual gyro wheel is about the size of your thumbnail. I've just started tracing things out, and I've gotten the gyros to spin up. I really love mechanical gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have great fun getting the package traced out and running. So, to be a bit more topical, the package of course needs 28V 400Hz for the gyros, 28VDC for something, and +/-15V for most of the electronics. Question - anyone figured out some clever solution for the 400Hz power? I faked it with a signal generator and power amp, but that's a bit bulky. I'm thinking I'll use one of the class-D amp ICs and a simple op-amp phase-shift sine generator. Topical in a more abstract way, strapdown systems really are very interesting. They require precise integration of the rate output over time to derive velocity and position, and really weren't practical until the 70's when small enough computers existed to do the requisite calculations. (I worked on the nav system for the Trident missile back in my Draper Labs days). ___ 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] OT - DC-10 gyros
An appropriate (but small) Group already exists: http://tech.groups.yahoo.com/group/Aerospace_Hardware_Collectors_Group/ -John === > Yeah I'd join a gyro-nuts group. I have a shelf full of weird gyros, a > stable > platform, other gyro stuff. I made a little power supply to make 28 volts > 3 > phase 400 Hz, found it in an app note, for running a set of three tiny > rate > gyros I picked up. I'll go dig it out and let you know. > > Peter > > On 3/27/2013 4:40 PM, Bill Ezell wrote: >> Well, I can come up with something topical, read on. :) >> >> I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of >> course, I >> had to buy it. >> >> What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 >> that >> was stripped for parts around 2000. The gyro included the pull tag with >> tail >> number, the license number of the A&P mechanic that pulled it, and some >> other >> cool stuff. >> >> What it turned out to really be is two gyros with two sets of >> electronics in >> one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, >> it's a >> strapdown system. The actual gyro wheel is about the size of your >> thumbnail. >> I've just started tracing things out, and I've gotten the gyros to spin >> up. I >> really love mechanical gyros for some reason, too bad there's not a >> gyro-nuts >> group. I'm going to have great fun getting the package traced out and >> running. >> >> So, to be a bit more topical, the package of course needs 28V 400Hz for >> the >> gyros, 28VDC for something, and +/-15V for most of the electronics. >> >> Question - anyone figured out some clever solution for the 400Hz power? >> I >> faked it with a signal generator and power amp, but that's a bit bulky. >> I'm >> thinking I'll use one of the class-D amp ICs and a simple op-amp >> phase-shift >> sine generator. >> >> Topical in a more abstract way, strapdown systems really are very >> interesting. >> They require precise integration of the rate output over time to derive >> velocity and position, and really weren't practical until the 70's when >> small >> enough computers existed to do the requisite calculations. (I worked on >> the >> nav system for the Trident missile back in my Draper Labs days). >> > > ___ > 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] OT - DC-10 gyros
Hi For that kind of power, I'd dig out an audio transformer and drive it with something like an LM-380. Bob On Mar 27, 2013, at 6:59 PM, Bill Ezell wrote: > I neglected to mention that. The DC resistance of the motor windings is > roughly 200 ohms. I estimate the power draw is < 2 watts. Haven't measured > the inductance. > > I probably could just use some FETs and build a simple class-B amp. The sine > wave doesn't have to be absolutely pure. Frequency stability (at least, in a > real application) is more important, since the gyro response depends upon the > rotational speed of the wheel. Not that I'm going to actually use it for > anything other than just getting it working. :) > > On 03/27/2013 6:21 PM, time-nuts-requ...@febo.com wrote: >> For "thumbsized" gyros, the power-drain is probably very slight. > > -- > Bill Ezell > > They said 'Windows or better' > so I used Linux. > > ___ > 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] OT - DC-10 gyros
The circuit I built used a ULN3751Z (TO-220) amplifier chip and some capacitors to create the phase shifts for making 3 phase. Very simple oscillator circuit. Haven't found the docs yet but found the unit itself. On 3/27/2013 6:59 PM, Bill Ezell wrote: I neglected to mention that. The DC resistance of the motor windings is roughly 200 ohms. I estimate the power draw is < 2 watts. Haven't measured the inductance. I probably could just use some FETs and build a simple class-B amp. The sine wave doesn't have to be absolutely pure. Frequency stability (at least, in a real application) is more important, since the gyro response depends upon the rotational speed of the wheel. Not that I'm going to actually use it for anything other than just getting it working. :) On 03/27/2013 6:21 PM, time-nuts-requ...@febo.com wrote: For "thumbsized" gyros, the power-drain is probably very slight. ___ 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] Win XP and NIST time
Orin writes: > If you use those, you have to lock the thread you are timing to one > CPU/Core as the performance counters are per CPU/Core and can get > out of step. Or you can force your thread onto one CPU for the > QueryPerformanceCounter call. This seems to be a bad idea to me as > it would add an indeterminate time before querying the counter > (indeterminate as if you are running on a different CPU, the OS > would have to switch to the one you requested). In the WWV3 program I posted about some time ago, I use these calls to precisely calculate sleep times between second pulses, with excellent results (accurate to within human perception, not sure about microsecond accuracy). This does not mean that the timing cannot be temporarily off for one beep, but overall it is extremely precise. This was the only solution I could find for getting the sleep times correct, since they vary from one second to the next depending on how much time the program actually slept on the previous call (Windows does not guarantee that sleep times will be exact). The resolution for sleeping is also one millisecond, as I recall, and you need better timing than that in order to keep the beeps consistent. Generally, though, if you don't have an application or system function stalling the system, and the hardware is fast enough, you should be able to get away with all sorts of real-time use, as long as you accept that one day the machine might miss something (preferably not during a Cat III ILS approach). -- Anthony ___ 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] OT - DC-10 gyros
Is this part of an HSI (horizontal situation indicator), ADI (attitude director indicator), INS (inertial navigation system), or autopilot? Are the bearings dust? Sounds like fun to play with though. What do you plan to do with it? Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bill Ezell Sent: Wednesday, March 27, 2013 3:40 PM To: time-nuts@febo.com Subject: [time-nuts] OT - DC-10 gyros Well, I can come up with something topical, read on. :) I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had to buy it. What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that was stripped for parts around 2000. The gyro included the pull tag with tail number, the license number of the A&P mechanic that pulled it, and some other cool stuff. What it turned out to really be is two gyros with two sets of electronics in one box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown system. The actual gyro wheel is about the size of your thumbnail. I've just started tracing things out, and I've gotten the gyros to spin up. I really love mechanical gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have great fun getting the package traced out and running. So, to be a bit more topical, the package of course needs 28V 400Hz for the gyros, 28VDC for something, and +/-15V for most of the electronics. Question - anyone figured out some clever solution for the 400Hz power? I faked it with a signal generator and power amp, but that's a bit bulky. I'm thinking I'll use one of the class-D amp ICs and a simple op-amp phase-shift sine generator. Topical in a more abstract way, strapdown systems really are very interesting. They require precise integration of the rate output over time to derive velocity and position, and really weren't practical until the 70's when small enough computers existed to do the requisite calculations. (I worked on the nav system for the Trident missile back in my Draper Labs days). -- Bill Ezell They said 'Windows or better' so I used Linux. ___ 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] OT - DC-10 gyros
Bill Ezell; Your Gyro may require 3 phase, 400 cps, 28 vac, Sine wave. A simple "Buffered Phase Shift Oscillator" for 400 cps can create the Sine Wave. https://www.circuitlab.com/circuit/h6v28g/buffered-phase-shift-oscillator/https://www.circuitlab.com/circuit/bakd83/phase-shift-oscillator-ii/You will need to add an AGC to the output for frequency stability. A "3 Phase Generator" can create the 3 phase output.https://www.circuitlab.com/circuit/m4u5nw/3-phase-generator/ Add 3 Amplifiers (one for each phase) to reach voltage/power. If the Gyro is directional, it will take several hours to stabilize. Carl Refinance your home now Loans under 729K usually qualify for US GOV backed refinance programs http://thirdpartyoffers.juno.com/TGL3131/5153a0bf2812c20bf6124st04duc ___ 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] OT - DC-10 gyros
Hi If three phase is actually needed, I'd suggest something like a cheap PIC with three PWM outputs. Fairly simple R/C's on the outputs should be plenty good enough to filter out any crud. Good frequency stability / accurate phase shift / cheap. What's not to like …. Bob On Mar 27, 2013, at 9:44 PM, kb0...@juno.com wrote: > Bill Ezell; > > Your Gyro may require 3 phase, 400 cps, 28 vac, Sine wave. > > A simple "Buffered Phase Shift Oscillator" for 400 cps can create the Sine > Wave. > https://www.circuitlab.com/circuit/h6v28g/buffered-phase-shift-oscillator/https://www.circuitlab.com/circuit/bakd83/phase-shift-oscillator-ii/You > will need to add an AGC to the output for frequency stability. > A "3 Phase Generator" can create the 3 phase > output.https://www.circuitlab.com/circuit/m4u5nw/3-phase-generator/ Add 3 > Amplifiers (one for each phase) to reach voltage/power. > If the Gyro is directional, it will take several hours to stabilize. > > Carl > > Refinance your home now > Loans under 729K usually qualify for US GOV backed refinance programs > http://thirdpartyoffers.juno.com/TGL3131/5153a0bf2812c20bf6124st04duc > ___ > 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] OT - DC-10 gyros
I have a little dynamotor somewhere which makes 3 phase 400 Hz. Tiny little thing! Only puts out like 15 VA, and not very noisy either. IIRC is was called an "Instrument inverter" On 3/27/2013 9:55 PM, Bob Camp wrote: Hi If three phase is actually needed, I'd suggest something like a cheap PIC with three PWM outputs. Fairly simple R/C's on the outputs should be plenty good enough to filter out any crud. Good frequency stability / accurate phase shift / cheap. What's not to like …. Bob On Mar 27, 2013, at 9:44 PM, kb0...@juno.com wrote: Bill Ezell; Your Gyro may require 3 phase, 400 cps, 28 vac, Sine wave. A simple "Buffered Phase Shift Oscillator" for 400 cps can create the Sine Wave. https://www.circuitlab.com/circuit/h6v28g/buffered-phase-shift-oscillator/https://www.circuitlab.com/circuit/bakd83/phase-shift-oscillator-ii/You will need to add an AGC to the output for frequency stability. A "3 Phase Generator" can create the 3 phase output.https://www.circuitlab.com/circuit/m4u5nw/3-phase-generator/ Add 3 Amplifiers (one for each phase) to reach voltage/power. If the Gyro is directional, it will take several hours to stabilize. Carl Refinance your home now Loans under 729K usually qualify for US GOV backed refinance programs http://thirdpartyoffers.juno.com/TGL3131/5153a0bf2812c20bf6124st04duc ___ 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. - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1430 / Virus Database: 2641/5707 - Release Date: 03/27/13 ___ 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] OT - DC-10 gyros
On 3/27/13 3:20 PM, Bob Camp wrote: Eight ohms at 28 volts would be just a bit under 4 amps. It's also right at 100 watts. I'd be very surprised it you need anywhere near that much current. You probably want a pure sine wave to keep everything happy. A lot of the simple inverters are "sort of" sine waves. I think I'd vote for something like an cheap audio amp driven by a nice clean / stable 400 Hz tone. So, if I take my nice clean 10 MHz, rig up a counter that counts to 25,000, and a suitable PROM and DAC... (or run a DDS chip)... I think that would be a "clean and stable" 400 Hz. Of course, for the more mechanically inclined.. what about a big flywheel driving an alternator. You might be able to rejigger a car alternator. I don't recall how many poles they have..you might have to spin it pretty fast. ___ 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] OT - DC-10 gyros
It was almost certainly for powering a WWII vintage fluxgate compass system. -John == > I have a little dynamotor somewhere which makes 3 phase 400 Hz. Tiny > little > thing! Only puts out like 15 VA, and not very noisy either. IIRC is was > called > an "Instrument inverter" > > > > On 3/27/2013 9:55 PM, Bob Camp wrote: >> Hi >> >> If three phase is actually needed, I'd suggest something like a cheap >> PIC with three PWM outputs. Fairly simple R/C's on the outputs should be >> plenty good enough to filter out any crud. Good frequency stability / >> accurate phase shift / cheap. What's not to like . >> >> Bob >> >> On Mar 27, 2013, at 9:44 PM, kb0...@juno.com wrote: >> >>> Bill Ezell; >>> >>> Your Gyro may require 3 phase, 400 cps, 28 vac, Sine wave. >>> >>> A simple "Buffered Phase Shift Oscillator" for 400 cps can create the >>> Sine Wave. >>> https://www.circuitlab.com/circuit/h6v28g/buffered-phase-shift-oscillator/https://www.circuitlab.com/circuit/bakd83/phase-shift-oscillator-ii/You >>> will need to add an AGC to the output for frequency stability. >>> A "3 Phase Generator" can create the 3 phase >>> output.https://www.circuitlab.com/circuit/m4u5nw/3-phase-generator/ Add >>> 3 Amplifiers (one for each phase) to reach voltage/power. >>> If the Gyro is directional, it will take several hours to stabilize. >>> >>> Carl >>> >>> Refinance your home now >>> Loans under 729K usually qualify for US GOV backed refinance programs >>> http://thirdpartyoffers.juno.com/TGL3131/5153a0bf2812c20bf6124st04duc >>> ___ >>> 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. >> >> >> - >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 10.0.1430 / Virus Database: 2641/5707 - Release Date: 03/27/13 >> >> >> > > ___ > 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] OT - DC-10 gyros
On Mar 27, 2013, at 22:54, Jim Lux wrote: > On 3/27/13 3:20 PM, Bob Camp wrote: > > > Of course, for the more mechanically inclined.. what about a big flywheel > driving an alternator. You might be able to rejigger a car alternator. I > don't recall how many poles they have.. A motor driving a flywheel driving an alternator/generator is called a motor generator set. Some implementations are called a diesel electric locomotive. We used to use them as power conditioners for Cray class supercomputers. Also used by many home machinists to generate 3 phase from single phase power. Car alternators are generally 3 phase internally. Don't know if you could get 28vac out tho. ___ 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] OT - DC-10 gyros
If you need good 3 phase 400 Hz you can get a VFD which goes up that high and program it to just sit there making 400 Hz. On 3/27/2013 11:16 PM, bownes wrote: On Mar 27, 2013, at 22:54, Jim Lux wrote: On 3/27/13 3:20 PM, Bob Camp wrote: Of course, for the more mechanically inclined.. what about a big flywheel driving an alternator. You might be able to rejigger a car alternator. I don't recall how many poles they have.. A motor driving a flywheel driving an alternator/generator is called a motor generator set. Some implementations are called a diesel electric locomotive. We used to use them as power conditioners for Cray class supercomputers. Also used by many home machinists to generate 3 phase from single phase power. Car alternators are generally 3 phase internally. Don't know if you could get 28vac out tho. ___ 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. - No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1430 / Virus Database: 2641/5707 - Release Date: 03/27/13 ___ 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] OT - DC-10 gyros
Crikey - an alternator? Automotive alternators typically have 6 poles, which delivers 60 Hz at 1200 RPM. You would need to go to 8000 RPM to get 400 Hz, or a bit more than 133 revs per second. That's really humming along. When I was younger, and found a tank gyro about 3" in diameter, it needed 115 VAC 3 phase. I found an electronic 28 VDC to 115 VAC 400 Hz that was single phase. A capacitor to the third phase wire would spin it up after you started it by hand. The motor doesn't care if the excitation is sine or square. There is a bit more heat dissipation from the harmonics in the square wave, but nothing to worry about in a small motor. If you are a purist, as many list members are, you could build a six step inverter to cut down on the harmonics. To be practical, divide 10 MHz from a GPS disciplined oscillator (which is necessary to be talking about this in this group), use a transistor to switch any available DC into a suitable audio transformer, and resonate it to 400 Hz with some caps. There was a time when I'd have killed for that kind of souvenir from a Northwest aircraft, but now I just sit back and read about it with fading interest. Bill Hawkins ___ 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.
