Re: [time-nuts] Datum TS-2100 Rubidium
but the LPRO isn't designed (well, according to the spec) for GND != -VE So long as you don't introduce it to real ground (i.e. isolate it), it won't know that the -12V is floating below world ground :-) Dave ___ 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] Pictic II boards are here !
Morning Stanley, Good news! As I mentioned before, I am happy to act as a UK Post Office if youl'd like to send all the UK-bound boards to me. I am collaborating with Ian Muir in Wales (Time Nut member Gonzo) on this project, so between us we would like five boards please. If you can let me know the final cost, including postage over the big pond, I'll get PayPal to do their thing. Can you please tell me what size the boards are, then I can get some appropriate padded bags for onward despatch. TTFN, Peter Vince (England) On 20 July 2010 23:08, Stanley Reynolds stanley_reyno...@yahoo.com wrote: Paypal to stanley_reyno...@yahoo.com . Yes I still have extra boards. Stanley ___ 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] Datum TS-2100 Rubidium
On 07/21/2010 10:11 AM, David C. Partridge wrote: but the LPRO isn't designed (well, according to the spec) for GND != -VE So long as you don't introduce it to real ground (i.e. isolate it), it won't know that the -12V is floating below world ground :-) Doable, but surely chassi ground of the LPRO is also tied to electrical ground? Last time I looked around, it sure looked like things where tied to chassi too. If so you need to electrically isolate the whole LPRO. The 10 MHz is easy enough with a transformer. The control signals would not be too hard. Another solution is to let the -12 V lead also be chassi... which works but is prone to errors... Cheers, Magnus ___ 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] Frequency Divider Board Status
An udpate for everyone, I am STILL waiting for Stackpole Electronics thin film resistors which I ordered through Digikey. I have kicked Stackpole, but current delivery date promised is mid August. Regards, David Partridge ___ 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] PICTIC PICs UK programming
The parts are all coming in and the boards aren't far either, so I'll reiterate my previous offer of programming the PICs. If you already have your PIC(s), you can send them to me with a self-addressed envelope and I'll program them no charge. or I have six PICs left from a recent purchase that I can supply programmed for £4 posted for the first and £2.5 for each additional chip. To keep the SN low, please reply off list. cheers, ian _ If It Exists, You'll Find it on SEEK. Australia's #1 job site http://clk.atdmt.com/NMN/go/157639755/direct/01/ ___ 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] Function of cap to GND in isolation transformer circuit
Hi, I noticed in several circuits that the 10MHz isolation transformer in input and output circuits have a 6.8nF or 10nF capacitor to GND. How necessary is this for suppression of unwanted signals? Is the transformer itself not sufficient? I would expect common mode issues to be a bit worse with the cap in place. The circuit I refer to can be seen here: http://www.uploadarchief.net/files/download/cap2gnd.png The first one is an output as described in the Efratom FRK manual, the second one the input in the TADD-2 manual. Cheers, Joop ___ 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] Function of cap to GND in isolation transformer circuit
Hi The cap likely improves the VHF stability of the circuit. Bob On Jul 21, 2010, at 7:46 AM, Joop wrote: Hi, I noticed in several circuits that the 10MHz isolation transformer in input and output circuits have a 6.8nF or 10nF capacitor to GND. How necessary is this for suppression of unwanted signals? Is the transformer itself not sufficient? I would expect common mode issues to be a bit worse with the cap in place. The circuit I refer to can be seen here: http://www.uploadarchief.net/files/download/cap2gnd.png The first one is an output as described in the Efratom FRK manual, the second one the input in the TADD-2 manual. Cheers, Joop ___ 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] Pictic II boards are here !
Peter, Thank you for offering to help, don't send paypal yet, I will send you the boards then after we know your postal expense then we can do the paypal thing. Stanley - Original Message From: Peter Vince pvi...@theiet.org To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, July 21, 2010 3:39:54 AM Subject: Re: [time-nuts] Pictic II boards are here ! Morning Stanley, Good news! As I mentioned before, I am happy to act as a UK Post Office if youl'd like to send all the UK-bound boards to me. I am collaborating with Ian Muir in Wales (Time Nut member Gonzo) on this project, so between us we would like five boards please. If you can let me know the final cost, including postage over the big pond, I'll get PayPal to do their thing. Can you please tell me what size the boards are, then I can get some appropriate padded bags for onward despatch. TTFN, Peter Vince (England) On 20 July 2010 23:08, Stanley Reynolds stanley_reyno...@yahoo.com wrote: Paypal to stanley_reyno...@yahoo.com . Yes I still have extra boards. Stanley ___ 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] Function of cap to GND in isolation transformer circuit
Its to prevent 'earth loops' and avoid issues with DC and low frequency AC on the coax screen - usually its found only on tx or rx end- not both- depends on the installation which practice is followed. Telcos tend to solid ground at the send end and cap ground at the rx end. And yes- it can make things worse-again depending on the installation. If you have the option of hard ground or cap ground at both ends you can select which combination gives the best result. This is usually only an issue with long runs of coax cable. DaveB, NZ - Original Message - From: Joop l...@xs4all.nl To: Joop l...@xs4all.nl Cc: time-nuts@febo.com Sent: Wednesday, July 21, 2010 11:46 PM Subject: [time-nuts] Function of cap to GND in isolation transformer circuit Hi, I noticed in several circuits that the 10MHz isolation transformer in input and output circuits have a 6.8nF or 10nF capacitor to GND. How necessary is this for suppression of unwanted signals? Is the transformer itself not sufficient? I would expect common mode issues to be a bit worse with the cap in place. The circuit I refer to can be seen here: http://www.uploadarchief.net/files/download/cap2gnd.png The first one is an output as described in the Efratom FRK manual, the second one the input in the TADD-2 manual. Cheers, Joop ___ 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] PLGR II on ebay
Please pardon the blatent plug, but this is a rare one. I've just listed a Rockwell PLGR II dual frequency GPS on ebay. Search for item No. 260638851411 Thanks, Robert G8RPI. ___ 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] Datum TS-2100 Rubidium
Ground is chassis ground as far as I remember, and the LPRO was bolted straight on the chassis. RobK -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: 21 July 2010 10:52 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Datum TS-2100 Rubidium On 07/21/2010 10:11 AM, David C. Partridge wrote: but the LPRO isn't designed (well, according to the spec) for GND != -VE So long as you don't introduce it to real ground (i.e. isolate it), it won't know that the -12V is floating below world ground :-) Doable, but surely chassi ground of the LPRO is also tied to electrical ground? Last time I looked around, it sure looked like things where tied to chassi too. If so you need to electrically isolate the whole LPRO. The 10 MHz is easy enough with a transformer. The control signals would not be too hard. Another solution is to let the -12 V lead also be chassi... which works but is prone to errors... Cheers, Magnus ___ 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] Datum TS-2100 Rubidium
...and according to the post from Greg Dowd (who was on the design team at Datum), it had a 24V PSU as an add on for the option. Rob K -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: 21 July 2010 10:52 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Datum TS-2100 Rubidium On 07/21/2010 10:11 AM, David C. Partridge wrote: but the LPRO isn't designed (well, according to the spec) for GND != -VE So long as you don't introduce it to real ground (i.e. isolate it), it won't know that the -12V is floating below world ground :-) Doable, but surely chassi ground of the LPRO is also tied to electrical ground? Last time I looked around, it sure looked like things where tied to chassi too. If so you need to electrically isolate the whole LPRO. The 10 MHz is easy enough with a transformer. The control signals would not be too hard. Another solution is to let the -12 V lead also be chassi... which works but is prone to errors... Cheers, Magnus ___ 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] Datum TS-2100 Rubidium
In which case if the lpro needs +24, then use a buck-boost 12-24V DC-DC converter. Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rob Kimberley Sent: 21 July 2010 16:08 To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Datum TS-2100 Rubidium Ground is chassis ground as far as I remember, and the LPRO was bolted straight on the chassis. RobK -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: 21 July 2010 10:52 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Datum TS-2100 Rubidium On 07/21/2010 10:11 AM, David C. Partridge wrote: but the LPRO isn't designed (well, according to the spec) for GND != -VE So long as you don't introduce it to real ground (i.e. isolate it), it won't know that the -12V is floating below world ground :-) Doable, but surely chassi ground of the LPRO is also tied to electrical ground? Last time I looked around, it sure looked like things where tied to chassi too. If so you need to electrically isolate the whole LPRO. The 10 MHz is easy enough with a transformer. The control signals would not be too hard. Another solution is to let the -12 V lead also be chassi... which works but is prone to errors... Cheers, Magnus ___ 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] Datum TS-2100 Rubidium
My first email from yesterday I think got rejected or put in queue because I tried to attach a picture... Hopefully this will make it through. I *think* the Rb model had a slightly different top panel (judging from the few pictures I've seen)... Probably made to either absorb some of the heat from the LPRO or maybe milled out some material for clearance. Here's some pics of the inside of my TS2100... I would assume the LPRO would mount in the front left area, and the dc-dc converter would mount behind the PSU on the right-back. http://www.rabel.org/archives/Images/TS2100/ I got lucky when I bought mine ages ago that it had the MTI OCXO in it instead of the usual TCXO. I still wish it had a Rb... I have a spare LPRO sitting around and would love to wire it into this puppy! It looks like there are two possible points for the LPRO to plug-in... But my guess would be for that center gray connector. I know I've seen older model TS2100's that had an additional AUI connector on the rear. I don't know how different the board inside would be. On a side note, anyone else notice that the TS2100 has a slightly higher network-delay than other network time servers? Delay Offset Jitter *NET4501.GPS.0.752 -0.042 0.203 +PRAECIS.GPS.0.810 -0.091 0.589 +TS2100 .GPS.5.074 -0.509 0.535 +NTS100 .IRIG. 0.401 -0.155 3.647 ___ 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] Efratom MGPS Manual
Am still looking for an Efratom MGPS manual... copy, scan... or anything at all on it. Would be nice to know how to make use of the RS-232 connection on this GPS receiver!!! Thanks! Mark Sent from my iPhone ___ 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] Pictic II boards are here !
So, do we now have available, an up to date (a moving target with Mouser, I acknowledge) parts list and stock numbers for correct resistors(trim), FETs, and ICs? Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 US Cell: +1-240-425-7335 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. ___ 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] Datum TS-2100 Rubidium
Are you sure? I honestly thought we just bolted it in the 1U chassis. I know earlier Datum units with the larger FRS Rbs went into 2U chassis. Rob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Greg Dowd Sent: 20 July 2010 6:20 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Datum TS-2100 Rubidium I think the Rb version went in a taller case? As for the reboot, probably depends on where you are probing :-) My proto unit from 1996 is still happily ticking along on my bench in the lab with an MTI oven that still has tuning range. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Julien Goodwin Sent: Tuesday, June 29, 2010 4:27 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Datum TS-2100 Rubidium On 28/06/10 21:36, Julien Goodwin wrote: Up next is to convert the darn thing to Rubidium, like it was meant to be when I purchased it (insert rant here). OK so the pinout vaguely matches, the TS-2100 is *very* twitchy on the alarm circuits, even a 1Mohm scope (well, it's 1M in theory, cheap Rigol[1]) tripped it to reboot a few times. But where in the world are you supposed to *put* the darn LPRO oscillator, it's too tall to fit above the board, and there doesn't look to be enough room between the back of the front panel and the main board. I'm also not sure about the power supply thing, seeing only the single post to time-nuts about it. I'd love photos, but I'd assume that most people that have one it sits in a rack running. Thanks, Julien 1: Actually 'tis one of the 50Mhz units hacked to 100Mhz operation, a very nice Tek 11k analog scope was reserved, but the seller appears to not want my business going silent after several prods. ___ 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] firmware updates for Jackson Labs GPSDO
Hi guys, for those of you that have Jackson Labs Technologies, Inc. products we have placed the latest firmware updates onto our web-site under the support tab: _http://www.jackson-labs.com/support.html_ (http://www.jackson-labs.com/support.html) This has been the first update since August of 2008 for Fury, so we left the previous version on the website as well since that is working quite well. The following improvements have been made: Fury GPSDO: * Added the NMEA output sentence $GPRMC to the $GPGGA command output. Both sentences are generated by default when the GPS:GPGGA 1 command is sent to Fury. This is useful since the RMC command includes additional info such as the date. Both sentences are now enabled/disabled together. FireFly-IIA based products (including ULN-2550 and ULN-1100 GPSDO): * Fixed various minor issues such as NMEA period being 1.1s in holdover * Performance improvements such as when entering/exiting holdover * New antenna delay command can now be used to shift the 1PPS output in 1ns steps * A new sync command allows enabling the 1PPS pulse even when no GPS antenna has been connected * Various additional Gyro commands were added FireFly-1A GPSDO: * Fixed various minor issues, such as \cr\cr\lf double termination on the NMEA sentence, the NMEA output having a 1.1s period rather than a 1.0s period in holdover, and others * Various performance improvements especially when coming out of holdover A description of the new FireFly-IIA software features is available under the documentation link in the support page. We hope this helps, and as always welcome comments, bug notifications, and questions. bye, Said ___ 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] A different timenuts interest
The problem is straight forward, except for sensing the position of the pendulum so the impulse is applied at the correct phase. There must be a bunch of published designs, but if I were to try it, I'd use something optical or capacitive. For optical, I'd put a annular ring of IR LED/Phototransistor assemblies around the center, wired OR the outputs, and use the signal to trigger the impulse. The bottom of the pendulum should be polished or mirrored. For capacitive, I'd copy a proximity detector circuit and use that. One plate would be the pendulum, the other an annular conducting ring just below it. It might also work with two, concentric rings and an electrically isolated pendulum. Best, -John === Hi all, I have been asked to help with the construction of a Foucault pendulum. This is a long pendulum which oscillates in a slow stately fashion in a fixed plane which appears to move as the earth rotates. In reality the surrounding environment is really moving relative to the plane of oscillation. The pendulum requires a sustaining system to compensate for the inevitable energy loss with each swing. The system is located in the building and therefore rotates relative to the pendulum. It needs to provide an impulse which does not affect the plane of oscillation of the pendulum. I was thinking of an electromagnet located below the centre of the swing which would be pulsed appropriately as the bob passes over it. Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Cheers, Morris ___ 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] A different timenuts interest
On 07/22/2010 02:13 AM, Morris Odell wrote: Hi all, I have been asked to help with the construction of a Foucault pendulum. This is a long pendulum which oscillates in a slow stately fashion in a fixed plane which appears to move as the earth rotates. In reality the surrounding environment is really moving relative to the plane of oscillation. The pendulum requires a sustaining system to compensate for the inevitable energy loss with each swing. The system is located in the building and therefore rotates relative to the pendulum. It needs to provide an impulse which does not affect the plane of oscillation of the pendulum. I was thinking of an electromagnet located below the centre of the swing which would be pulsed appropriately as the bob passes over it. Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Just as you slightly push away the bob you could also attract it as it comes back... then you get a push-pull action. A coil in the center would have a fairly low plane-shifting action. Cheers, Magnus ___ 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] A different timenuts interest
At 08:13 PM 7/21/2010, Morris Odell wrote... Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Scientific American, back in June 1958, covered many details of Foucault pendulums, from Charron pivots to drive systems. The article was later reprinted in The Amateur Scientist book. It describes a magnetic drive which applies force near the pivot and another which sits underneath the pendulum. There's also a mechanical drive, as described near the bottom of this page: http://science-design.com/pages/foucault_pendulum_background/ ___ 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] A different timenuts interest
Hi If you use the mechanical system (raise and lower the pivot point): Can you use the strain on the pivot to get the location information? Bob On Jul 21, 2010, at 8:53 PM, Mike S wrote: At 08:13 PM 7/21/2010, Morris Odell wrote... Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Scientific American, back in June 1958, covered many details of Foucault pendulums, from Charron pivots to drive systems. The article was later reprinted in The Amateur Scientist book. It describes a magnetic drive which applies force near the pivot and another which sits underneath the pendulum. There's also a mechanical drive, as described near the bottom of this page: http://science-design.com/pages/foucault_pendulum_background/ ___ 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] A different timenuts interest
... Foucault pendulum ... Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Several years ago, I found a web site for a commercial place that made them for museums. (I forget why I was looking for that sort of stuff.) You might find interesting stuff/ideas via google but I didn't find a similar site with a bit of searching. -- Here is what I would try: Put a magnet on the bottom of the pendulum. Put a coil below it. (obviously centered) Use the coil as a sensor to measure the timing. Use the coil as a motor to pull the pendulum every N-th swing. The question is how accurately centered do the magnet and coil have to be? I don't know. It sounds like a fun mixture of theory and engineering. One of the variables is how far away is the pendulum when you are pulling. The farther away it is, the smaller angle you have from the ideal. You can change that by varying the start/stop times on the pull pulse. I'd probably put the coil on a crude X-Y table, set it up as good as I could, then see if it worked. Then I would deliberately move it off a bit and see what happened. Or try to servo it to the best place, probably by manual changes every day or week or ??? I'm assuming this is for a school or museum. The required positional accuracy is actually a real science experiment. The idea of experiment to test an idea is more important than the basic Foucault pendulum itself so you get two exhibits in one. Of course, another question is how fast does it decay? Or rather, how long will it run with no energy input? This says 2 hours: http://www.cmnh.org/site/AtTheMuseum/OnExhibit/PermanentExhibits/Foucault.as px for a 270 lb bob, but I don't know how tall that is. (But it says 6.2 seconds, so I should be able to calculate it.) -- These are my opinions, not necessarily my employer's. 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] A different timenuts interest
On 7/21/2010 7:13 PM, Morris Odell wrote: Hi all, I have been asked to help with the construction of a Foucault pendulum. This is a long pendulum which oscillates in a slow stately fashion in a fixed plane which appears to move as the earth rotates. In reality the surrounding environment is really moving relative to the plane of oscillation. The pendulum requires a sustaining system to compensate for the inevitable energy loss with each swing. The system is located in the building and therefore rotates relative to the pendulum. It needs to provide an impulse which does not affect the plane of oscillation of the pendulum. I was thinking of an electromagnet located below the centre of the swing which would be pulsed appropriately as the bob passes over it. Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Cheers, Morris ___ 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. Hello Morris: You might contact Fermi National Accelerator Lab in Batavia Illinois at www.fnal.gov . There Foucault pendulum is sixteen stories from the suspension point to the atrium floor,it's impulse device is buried in the sand under the bob. They may even have a picture of it on there web site. Try the public information office they should be able to get in contact with the people that maintain it. If you are unable to get any help let me know as I might have some contacts there that would help. Good Luck Don Henderickx ___ 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] A different timenuts interest
Griffith Park in LA operates a Foucault pendulum that's been going for at least 70 years (don't ask how I know). They might have a writeup somewhere. I think te pivot was a simple clamp holding the piano wire. You'd think it would fail from stress, but the pendulum is very long, so the angle of the swing is very small. I think the drive actually was done close to the pivot via a magnet on the wire rather than at the bottom. To start the pendulum off, a string was tied to hold the pendulum cocked and the string simply burned with a match. A perfect no-torque start... A simple optical interruptor driving something like a basic stamp and a ring electromagnet with a PM on the support wire will allow proper timing. You will be surprised at how little energy is required to keep it going; it can be roughly calculated from the ball diameter. The beauty of this system is that the exact frequency of the pendulum is not important. First order temperature correction can be done in the microprocessor. Send some pix when you get it going... Don Latham. Hal Murray ... Foucault pendulum ... Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Several years ago, I found a web site for a commercial place that made them for museums. (I forget why I was looking for that sort of stuff.) You might find interesting stuff/ideas via google but I didn't find a similar site with a bit of searching. -- Here is what I would try: Put a magnet on the bottom of the pendulum. Put a coil below it. (obviously centered) Use the coil as a sensor to measure the timing. Use the coil as a motor to pull the pendulum every N-th swing. The question is how accurately centered do the magnet and coil have to be? I don't know. It sounds like a fun mixture of theory and engineering. One of the variables is how far away is the pendulum when you are pulling. The farther away it is, the smaller angle you have from the ideal. You can change that by varying the start/stop times on the pull pulse. I'd probably put the coil on a crude X-Y table, set it up as good as I could, then see if it worked. Then I would deliberately move it off a bit and see what happened. Or try to servo it to the best place, probably by manual changes every day or week or ??? I'm assuming this is for a school or museum. The required positional accuracy is actually a real science experiment. The idea of experiment to test an idea is more important than the basic Foucault pendulum itself so you get two exhibits in one. Of course, another question is how fast does it decay? Or rather, how long will it run with no energy input? This says 2 hours: http://www.cmnh.org/site/AtTheMuseum/OnExhibit/PermanentExhibits/Foucault.as px for a 270 lb bob, but I don't know how tall that is. (But it says 6.2 seconds, so I should be able to calculate it.) -- These are my opinions, not necessarily my employer's. 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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.
Re: [time-nuts] A different timenuts interest
Hal Murray wrote: Several years ago, I found a web site for a commercial place that made them for museums. (I forget why I was looking for that sort of stuff.) You might find interesting stuff/ideas via google but I didn't find a similar site with a bit of searching. The Museum of Science and Industry in Chicago had one when I lived there in the 1960's. Rick N6RK ___ 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] A different timenuts interest
The Museum of Science and Industry in Chicago had one when I lived there in the 1960's. You lived at the Museum of Science and Industry? :) Sorry, couldn't resist. But, you actually can live there for a month: http://www.msichicago.org/matm/ Randy. ___ 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] A different timenuts interest
There is at least one in DC, at the Smithsonian iirc. RPI, where I went to college, had one in the 3 story stairwell in the library. Don't know if it is still there. I remember one someplace in London too. Someone mentioned temperature compensation. What would you need to compensate for? Temp change in the wire wouldn't effect the rotation as far as I can tell. Swing length might be different based on temp of the wire I guess, but with a long pendulum, I think the magnet is going to way overcome that issue. The one @ RPI had issues due to air movement in the shaft, but that's a different problem. I suppose the right method is to use a GPS disciplined oscillator and the appropriate divider to drive the magnet under the floor. :) To cut down in draft induced drift and jitter, you'd have to put the whole thing in a vacuum though! On Wed, Jul 21, 2010 at 10:13 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: Hal Murray wrote: Several years ago, I found a web site for a commercial place that made them for museums. (I forget why I was looking for that sort of stuff.) You might find interesting stuff/ideas via google but I didn't find a similar site with a bit of searching. The Museum of Science and Industry in Chicago had one when I lived there in the 1960's. Rick N6RK ___ 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] A different timenuts interest
Well, Morris, this does sound interesting. You've had some pretty conventional replies, so let's up the ante a bit. If you need to know where something macroscopic is in space, attach a GPS receiver to it. Then program some PIC device (lots of advice about that on this list) to compute optimum impulse points after calculating an error that can be corrected by the minimum possible impulse. NASA could advise you about small impulse rocket systems. They may even have a few Space Shuttle micro thrusters and fuel systems for sale. You may be able to drop fuel and oxidizer into the tanks at certain positions of the bob. The bob on a Foucault pendulum is usually quite massive, so there's no reason why it can't be inexpensive lead-acid batteries that are recharged by solar cells. I'm sure you'd save money over mechanisms to move the pivot or huge magnets buried in the floor. Given present unemployment levels, you may be able to hire a person to deliver impulses to the bob as required. But most of the world has automated such systems because people are not reliable. Heck, you could build a pendulum and a metaphor for our times. Best regards, Bill Hawkins (also on Jack's BA list) -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Morris Odell Sent: Wednesday, July 21, 2010 7:13 PM To: time-nuts@febo.com Subject: [time-nuts] A different timenuts interest Hi all, I have been asked to help with the construction of a Foucault pendulum. This is a long pendulum which oscillates in a slow stately fashion in a fixed plane which appears to move as the earth rotates. In reality the surrounding environment is really moving relative to the plane of oscillation. The pendulum requires a sustaining system to compensate for the inevitable energy loss with each swing. The system is located in the building and therefore rotates relative to the pendulum. It needs to provide an impulse which does not affect the plane of oscillation of the pendulum. I was thinking of an electromagnet located below the centre of the swing which would be pulsed appropriately as the bob passes over it. Has anyone here had any experience with such a system of have any suggestions regarding the sustaining system? This is an interesting and challenging project. Cheers, Morris ___ 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] A different timenuts interest
Silly me, I just realized you need to compensate for the change in length with temperature. This sounds like a great project! On Wed, Jul 21, 2010 at 10:26 PM, Bob Bownes bow...@gmail.com wrote: There is at least one in DC, at the Smithsonian iirc. RPI, where I went to college, had one in the 3 story stairwell in the library. Don't know if it is still there. I remember one someplace in London too. Someone mentioned temperature compensation. What would you need to compensate for? Temp change in the wire wouldn't effect the rotation as far as I can tell. Swing length might be different based on temp of the wire I guess, but with a long pendulum, I think the magnet is going to way overcome that issue. The one @ RPI had issues due to air movement in the shaft, but that's a different problem. I suppose the right method is to use a GPS disciplined oscillator and the appropriate divider to drive the magnet under the floor. :) To cut down in draft induced drift and jitter, you'd have to put the whole thing in a vacuum though! On Wed, Jul 21, 2010 at 10:13 PM, Richard (Rick) Karlquist rich...@karlquist.com wrote: Hal Murray wrote: Several years ago, I found a web site for a commercial place that made them for museums. (I forget why I was looking for that sort of stuff.) You might find interesting stuff/ideas via google but I didn't find a similar site with a bit of searching. The Museum of Science and Industry in Chicago had one when I lived there in the 1960's. Rick N6RK ___ 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] A different timenuts interest
bow...@gmail.com said: Silly me, I just realized you need to compensate for the change in length with temperature. It depends... If your setup to replace the energy is PLLed to the pendulum position it doesn't need to know the period. (at least not very accurately) -- These are my opinions, not necessarily my employer's. 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] A different timenuts interest
I remember one someplace in London too. Science Museum in South Kensington, I'd expect, but I've not been there 20+ years. -John Someone mentioned temperature compensation. What would you need to compensate for? Temp change in the wire wouldn't effect the rotation as far as I can tell. Swing length might be different based on temp of the wire I guess, but with a long pendulum, I think the magnet is going to way overcome that issue. The one @ RPI had issues due to air movement in the shaft, but that's a different problem. I suppose the right method is to use a GPS disciplined oscillator and the appropriate divider to drive the magnet under the floor. :) To cut down in draft induced drift and jitter, you'd have to put the whole thing in a vacuum though! You don't want to drive it from a clock, IMO. You want to make it a free-running oscillator. Period is irrelevant. -John == ___ 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] A different timenuts interest
[snip] The bob on a Foucault pendulum is usually quite massive, so there's no reason why it can't be inexpensive lead-acid batteries that are recharged by solar cells. IMO, there is no reason to put anything active on the bob. I'm sure you'd save money over mechanisms to move the pivot or huge magnets buried in the floor. The pendulum is very high Q. You don't want or need a lot of force. I'd guess a coil smaller than a coffee cup would be more than enough. Given present unemployment levels, you may be able to hire a person to deliver impulses to the bob as required. But most of the world has automated such systems because people are not reliable. True. When in China in about 1979, I was astounded they had Elevator Operators. Many of them, but they had more people than jobs. Heck, you could build a pendulum and a metaphor for our times. Best regards, Bill Hawkins (also on Jack's BA list) Best, -John ___ 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] 74AC175PC chips have arrived
These turned out to be made by Fairchild. If you expressed a desire to purchase one or more of these chips, I'll be contacting you soon with total cost. If you have a preference for packaging, please send me a note. Some evidently prefer the small flat rate box, although I'd planned to ship small quantities (1 or 2) via padded envelope. Thanks, Bob Berg ___ 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] Which Rubidium to Get?
I'm considering buying a rubidium standard, not that I really need one, just because I'm a Time Nut. I have some questions on what to look for and what to watch out for. I'll probably get one from either fluke.l or flyingbest on ePay. I know that they wear out. Is there any model I should look for or avoid? I see both Efratoms and Datums; some of the auctions claim more lamp life left for the Datums. I know that the mating connector for the rubidiums with an RF inside the d-sub connector are expensive. Is it really needed or is the header connector good enough? Some of them come with an output board (290295929282). Does this get me anything other than a Type-N output and a mating connector for the RF d-sub? Why is this one cheaper than just a rubidium? A programmable frequency output, such as this one (eBay item 290301888238), might be useful. Is it worthwhile or more trouble than it's worth? Are there any gotchas I should be aware of? Thanks, Brent ___ 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] A different timenuts interest
J. Forster wrote: The problem is straight forward, except for sensing the position of the pendulum so the impulse is applied at the correct phase. There must be a bunch of published designs, but if I were to try it, I'd use something optical or capacitive. For optical, I'd put a annular ring of IR LED/Phototransistor assemblies around the center, wired OR the outputs, and use the signal to trigger the impulse. The bottom of the pendulum should be polished or mirrored. The usual scheme is a couple of optical paths at the top of the pendulum with lenses to focus the beam down to a very small diameter (smaller than the wire diameter). The two optical paths are at 90 degrees to each other, and are logically anded either by using a pair of detectors/paths, or by using a mirror to fold the path. It's aligned with the pendulum perfectly stationary (i.e. it's been sitting still for a day or two) so the beam trigger occurs precisely at the center point. ___ 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] Function of cap to GND in isolation transformer circuit
Joop, The cap is isolate any DC from the transformer, The manual for TADD-1 has this iformation at the TAPR site has this manual http://www.tapr.org/~n8ur/TADD-1_Manual.pdf. On Wed, Jul 21st, 2010 at 9:46 PM, Joop l...@xs4all.nl wrote: Hi, I noticed in several circuits that the 10MHz isolation transformer in input and output circuits have a 6.8nF or 10nF capacitor to GND. How necessary is this for suppression of unwanted signals? Is the transformer itself not sufficient? I would expect common mode issues to be a bit worse with the cap in place. The circuit I refer to can be seen here: http://www.uploadarchief.net/files/download/cap2gnd.png The first one is an output as described in the Efratom FRK manual, the second one the input in the TADD-2 manual. Cheers, Joop ___ 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.
