[time-nuts] Clock Correction Algorithm
Hi! I am building a clock that fetches its time from a local NTP server (GPS synched machine). I am using a timer based on a 16 bit interrupt on an Arduino (ATmega328 clocked at 16 MHz). I am implementing an algorithm to steer the this clock (nothing as complicated as the NTP algorithms) and wanted your opinion regarding this. The clock is set by sending an NTP packet and setting the clock with the replied timestamp plus half of the round trip time. In a local LAN this seems a good solution. I am not after micro-second accuracy as this is a clock and our eyes don't recognize anything faster than 50 ms. Even then I am aiming for 1-10 ms maximum offset with the NTP server. So, I am thinking about this algorithm (1-4 are done once and then it will jump to a): 1. interval = 64 2. ncorrections = 0 3. lastcorrection = 0 4. lastset = now a. while (lastset - now) interval do nothing b. fetch time from NTP c. compute offset from local clock d. compute correction to be added/subtracted to each second for this interval (offset/interval) e. reset clock with time fetched from NTP and apply correction to clock (making the second longer or shorter as appropriate) f. lastset = now g. if lastcorrection = 0 then go to i h. if abs(lastcorrection - correction) max then go to r i. lastcorrection = correction j. ncorrections = ncorrections + 1 k. if ncorrections 3 go to a l. if interval = 1024 go to m l. interval = interval x 2 m. ncorrections = 0 n. lastcorrection = 0 r. interval = 64 s. ncorrections = 0 t. lastcorrection = 0 u. go to a What's your take regarding this matter? Any help will be appreciated. Cheers, Miguel ___ 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] SDR GPS
Has any of you played with this: http://www.sparkfun.com/products/8238 -- 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] SDR GPS
On Thu, 24 Nov 2011 11:19:37 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: Has any of you played with this: http://www.sparkfun.com/products/8238 I had a look at this (and a few other GPS SDR solutions) back a year or two ago and decided that they are either way too expensive or do not lend themselves well for time-nutty experimentation and are still too expensive. I guesstimate that a L1 GPS SDR receiver (SAW filter + LNA + down mixer + filter + second downmixer + filter + 8bit 40MHz ADC + FPGA) could be build with a budget of 500CHF at single pieces, rivaling the price of the sparkfun device you mentioned, while being 1) fully documented and 2) could lend itself to tinkering. Hence i dont think it's worth buying such a device (unless you are a software only guy who sees hardware as a necessary evil). An L1 + L2 receiver should be not that much more expenive, but the availability of filters for the L2 range is bad (you'd have to build one in microstrips) and depending on the exact design of the IF stage you'd have to doublicate the L1 path earlier or later for the L2 path. Hence i gues, a L1 + L2 reciever should have an additional cost of 100-200CHF (to the L1 only receiver) Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Clock Correction Algorithm
On Thu, 24 Nov 2011 10:14:17 + Miguel Gonçalves m...@miguelgoncalves.com wrote: The clock is set by sending an NTP packet and setting the clock with the replied timestamp plus half of the round trip time. In a local LAN this seems a good solution. I am not after micro-second accuracy as this is a clock and our eyes don't recognize anything faster than 50 ms. Even then I am aiming for 1-10 ms maximum offset with the NTP server. if you want to be better than 10ms, you can just use the value you get from the NTP server, raw, without any processing. The usuall RTT values in a LAN (light or moderate load) is around 100-200us. Ie if your NTP server doesn't take an exuberant amount of time to respond (which it should not anyways) and your LAN is not heavily loaded, you will be below 1ms in 99% of the time. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] DGPS@home
Hi all! I wonder what would be reasonable location accuracy if two cheap same type GPS modules will be several meters apart? I understand that it involves statistical numbers. Any idea? Say for a small robot. Thanks! - Henry -- ehydra.dyndns.info ___ 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] SDR GPS
Pricey, but allows to fly on high-attitude/speed. The region where money ist not so important ;-) - Henry Poul-Henning Kamp schrieb: Has any of you played with this: http://www.sparkfun.com/products/8238 -- ehydra.dyndns.info ___ 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] Low noise power supplies for time nuts circuitry
On Wed, 23 Nov 2011 04:50:49 -0800 Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: How well would a pair of cascaded 3 terminal regulators do - say a 7815 feeding a 7812. 78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Clock Correction Algorithm
On 24/11/2011, at 11:42, Attila Kinali att...@kinali.ch wrote: On Thu, 24 Nov 2011 10:14:17 + Miguel Gonçalves m...@miguelgoncalves.com wrote: The clock is set by sending an NTP packet and setting the clock with the replied timestamp plus half of the round trip time. In a local LAN this seems a good solution. I am not after micro-second accuracy as this is a clock and our eyes don't recognize anything faster than 50 ms. Even then I am aiming for 1-10 ms maximum offset with the NTP server. if you want to be better than 10ms, you can just use the value you get from the NTP server, raw, without any processing. The usuall RTT values in a LAN (light or moderate load) is around 100-200us. Ie if your NTP server doesn't take an exuberant amount of time to respond (which it should not anyways) and your LAN is not heavily loaded, you will be below 1ms in 99% of the time. Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. The proposed algorithm wants to correct that. Cheers, Miguel ___ 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] Clock Correction Algorithm
El 24/11/2011 13:56, Miguel Gonçalves escribió: Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. That is more than 400ppm error, that sounds quite high. Is the clock frequency of the Arduino so drifted? I would try first to check (and correct a bit) the source of that error. If the crystal frequency is ok, perhaps there is an error in the programming of the timer that generates the timing interrupt. Regards, Javier ___ 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] DGPS@home
Usually GPS receivers have DOP figures you can use to estimate the position precision. Maybe worth using timing receivers for position to increase the position accuracy. On Thu, Nov 24, 2011 at 1:01 PM, ehydra ehy...@arcor.de wrote: Hi all! I wonder what would be reasonable location accuracy if two cheap same type GPS modules will be several meters apart? I understand that it involves statistical numbers. Any idea? Say for a small robot. Thanks! - Henry -- ehydra.dyndns.info __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Clock Correction Algorithm
On Thu, 24 Nov 2011 12:56:31 + Miguel Gonçalves m...@miguelgoncalves.com wrote: Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. The proposed algorithm wants to correct that. Oh.. sorry.. i misunderstood your question. Yes the algorithm would work, though i'd rather use a pll style sytem. Ie, measure the differnce in time between your clock and your refrence. Calculate from this a correction value for the clock frequency (should be a simple multiplication by a constant factor). Low pass filter that correction value. This should also do away with all those special cases in your algorithm, as a PLL style algo is self stabilizing (unless you got the loop gain too high*). You will get at most a constant difference between your clock and the reference. This difference can be minimized by using a higher gain in the feedback loop (at the cost of stability). Also as Javier said, 400ppm is a quite high offset for a crystal. Or are you using a RC oscillator based RTC? (a lot of on chip RTCs are build that way) On the other hand, i once used a Atmel SAM7 RTC (or RTT in Atmel lingo) that is based on a RC Oscillator with +/- 30% accuracy. Using a simple calibration step (powering up the crystal oscillator every hour and using the crystal to measure the RTT frequency, setting this as new correction value, then going back to sleep for an hour) got me below 100ppm over a day in my tests (office enviroment, temperature variation probably below 2°C over a day, definitly less than 5°C, 30ppm crystal) Attila Kinali * this is a very very simplified view on PLL stability, but should be ok in this (software) context. Please consult a textbook on PLL desing for further information -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Clock Correction Algorithm
Hi Javier! Thanks for your help. On 24/11/2011, at 13:16, Javier Herrero jherr...@hvsistemas.es wrote: El 24/11/2011 13:56, Miguel Gonçalves escribió: Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. That is more than 400ppm error, that sounds quite high. Is the clock frequency of the Arduino so drifted? I would try first to check (and correct a bit) the source of that error. If the crystal frequency is ok, perhaps there is an error in the programming of the timer that generates the timing interrupt. I am using an Arduino Uno that presumably is running at 16 MHz. I am using a 16 bit timer with a 256 pre-scaler: 1600 / 256 = 62500 Hz 1 / 62500 = 16 us 65536 - 62500 = 3036 I am setting the counter to 3036 and let it overflow after 65535. If I check the error every second I see the clock getting behind correct time and after 60 seconds it's 25 ms apart from UTC. Perhaps I should increase the initial value from 3036 to 3036+25E6/(60/16). I will make the second shorter this way. What do you think? Cheers, Miguel Regards, Javier ___ 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] Clock Correction Algorithm
Hi!! On 24/11/2011, at 13:48, Attila Kinali att...@kinali.ch wrote: On Thu, 24 Nov 2011 12:56:31 + Miguel Gonçalves m...@miguelgoncalves.com wrote: Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. The proposed algorithm wants to correct that. Oh.. sorry.. i misunderstood your question. Yes the algorithm would work, though i'd rather use a pll style sytem. Ie, measure the differnce in time between your clock and your refrence. Calculate from this a correction value for the clock frequency (should be a simple multiplication by a constant factor). Low pass filter that correction value. I will investigate PLL. I don't want something overly complicated because this is a time display. I want less that 10 ms error and this goal is much better than needed for a clock. This should also do away with all those special cases in your algorithm, as a PLL style algo is self stabilizing (unless you got the loop gain too high*). You will get at most a constant difference between your clock and the reference. This difference can be minimized by using a higher gain in the feedback loop (at the cost of stability). This is exactly what I wanted. I really need to read about PLL. Also as Javier said, 400ppm is a quite high offset for a crystal. Or are you using a RC oscillator based RTC? (a lot of on chip RTCs are build that way) I am using the oscillator that comes with the Arduino. On the other hand, i once used a Atmel SAM7 RTC (or RTT in Atmel lingo) that is based on a RC Oscillator with +/- 30% accuracy. Using a simple calibration step (powering up the crystal oscillator every hour and using the crystal to measure the RTT frequency, setting this as new correction value, then going back to sleep for an hour) got me below 100ppm over a day in my tests (office enviroment, temperature variation probably below 2°C over a day, definitly less than 5°C, 30ppm crystal) I have a RTC that I am not using for this project that has 3.5ppm between -40C and 85C but I don't intend to use it because I want to keep this simple. Thanks a lot Atilla for your help. Cheers, Miguel ___ 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] Clocking a PIC16F628A from a Rubidium Standard
Greetings all, I have an Efratom 101 frequency standard with a 10 MHz TTL otput. I want to use this to clock a PIC 16F628A so I can make a frequency counter with a resolution of 1 Hz. I am going to use the design by EI9GQ here http://homepage.eircom.net/~ei9gq/counter.html . What I need to know is how i should go about electronically interfacing the TTL output from the rubidium standard so that it can clock the PIC. Has anyone on the list actually done this successfully? Thanks in advance, Steve G0XAR -- It is vain to do with more that which can be done with less.William of Occam Christmas has become a marketing gimmickany relationship between it and the celebration of charity, good will, peace to all mankind and the birth of Jesus are entirely co-incidental and I find this incredibly sad! ___ 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] Clock Correction Algorithm
On Thu, 24 Nov 2011 14:21:37 + Miguel Gonçalves m...@miguelgoncalves.com wrote: I am using an Arduino Uno that presumably is running at 16 MHz. I am using a 16 bit timer with a 256 pre-scaler: 1600 / 256 = 62500 Hz 1 / 62500 = 16 us 65536 - 62500 = 3036 I am setting the counter to 3036 and let it overflow after 65535. I'm not quite sure i understood you correctly, and i dont know anything about the arduino and the avr32. But usually, you set a timer to do a certain repetition rate. Ie raises an interrupt ever x clock cycles. Or to put it differently, you let the timer run freely, but let it call you when it's time to do something. How do you check for the overflow? If you check a flag in your main loop, this would explain the huge difference, as this polling will add a (not so) constant delay each time the timer overflows, until you start your timer again. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] SDR GPS
On 11/24/11 3:38 AM, Attila Kinali wrote: On Thu, 24 Nov 2011 11:19:37 + Poul-Henning Kampp...@phk.freebsd.dk wrote: Has any of you played with this: http://www.sparkfun.com/products/8238 I had a look at this (and a few other GPS SDR solutions) back a year or two ago and decided that they are either way too expensive or do not lend themselves well for time-nutty experimentation and are still too expensive. I guesstimate that a L1 GPS SDR receiver (SAW filter + LNA + down mixer + filter + second downmixer + filter + 8bit 40MHz ADC + FPGA) could be build with a budget of 500CHF at single pieces, rivaling the price of the sparkfun device you mentioned, while being 1) fully documented and 2) could lend itself to tinkering. Hence i dont think it's worth buying such a device (unless you are a software only guy who sees hardware as a necessary evil). An L1 + L2 receiver should be not that much more expenive, but the availability of filters for the L2 range is bad (you'd have to build one in microstrips) and depending on the exact design of the IF stage you'd have to doublicate the L1 path earlier or later for the L2 path. Hence i gues, a L1 + L2 reciever should have an additional cost of 100-200CHF (to the L1 only receiver) Attila Kinali A typical spaceflight multiband design has a LNA and wideband filter up front (500MHz) followed by 3 parallel chains of filters and amps followed by a single bit quantizer. You might be able to find those ceramic filter based filters, which are reasonably small (Lark Engineering and others make these). If it was a full custom, the filters might cost a bit in NRE, but since others are also doing GPS, it might be a stock item. There's an ION paper from earlier this year by Courtney Duncan that describes our receiver. : Duncan, C.B., Robison, D.E., Koelewyn, C. Lee, Software Defined GPS Receiver for International Space Station, Proceedings of the 2011 International Technical Meeting of The Institute of Navigation, San Diego, CA, January 2011, pp. 982-988. http://trs-new.jpl.nasa.gov/dspace/handle/2014/41781 http://hdl.handle.net/2014/41781 ___ 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] Low noise power supplies for time nuts circuitry
From a noise and long term stability standpoint, it would not be better than the last device in the chain, and the 78xx series is not great. But you would gain additional ripple and line variation rejection, so if that's what you need to do, it may help. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Chuck Forsberg WA7KGX N2469R c...@omen.com Sender: time-nuts-boun...@febo.com Date: Wed, 23 Nov 2011 04:50:49 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry How well would a pair of cascaded 3 terminal regulators do - say a 7815 feeding a 7812. How sensitive are each of a Thunderbolt's 3 supplies to noise? On 11/23/2011 04:13 AM, Attila Kinali wrote: On Tue, 22 Nov 2011 12:38:43 -0500 Bob Campli...@rtty.us wrote: There are a couple of circuits (low noise op-amp based) that can generate lower noise than what he's shown. What circuits would that be? Attila Kinali -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] Clocking a PIC16F628A from a Rubidium Standard
On Thu, 24 Nov 2011 14:41:24 + Stephen Farthing squir...@gmail.com wrote: I have an Efratom 101 frequency standard with a 10 MHz TTL otput. I want to use this to clock a PIC 16F628A so I can make a frequency counter with a resolution of 1 Hz. I am going to use the design by EI9GQ here http://homepage.eircom.net/~ei9gq/counter.html . What I need to know is how i should go about electronically interfacing the TTL output from the rubidium standard so that it can clock the PIC. Has anyone on the list actually done this successfully? Have a look at the PIC 16F628 data sheet, it will tell you the requirements for the clock input and there should be circuit for external clock signal listed. If it's not in the datasheet, it should be in an appnote. Usually, chips accept sinusoidal and rectangular inputs up to 0V-VDD swing. If i'm reading the schematic correctly and the PIC runs with 5V, then you should be able to just feed the Efratom output directly to the PIC. Maybe, a ceramic 100n capacitor in this line should be used to do a DC isolation (1u cermaic should do as well). Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Low noise power supplies for time nuts circuitry
At 2:28 PM + 11/24/11, time-nuts-requ...@febo.com wrote: Message: 3 Date: Thu, 24 Nov 2011 13:22:38 +0100 From: Attila Kinali att...@kinali.ch To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry Message-ID: 2024132238.0c810b78.att...@kinali.ch Content-Type: text/plain; charset=US-ASCII On Wed, 23 Nov 2011 04:50:49 -0800 Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: How well would a pair of cascaded 3 terminal regulators do - say a 7815 feeding a 7812. 78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. What I see done in low-noise circuits is a low-noise opamp used as a linear voltage regulator to clean up the output of a 78xx or the like regulator. Joe Gwinn ___ 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] Clock Correction Algorithm
El 24/11/2011 15:21, Miguel Gonçalves escribió: I am using an Arduino Uno that presumably is running at 16 MHz. I am using a 16 bit timer with a 256 pre-scaler: 1600 / 256 = 62500 Hz 1 / 62500 = 16 us 65536 - 62500 = 3036 I am setting the counter to 3036 and let it overflow after 65535. If I check the error every second I see the clock getting behind correct time and after 60 seconds it's 25 ms apart from UTC. Perhaps I should increase the initial value from 3036 to 3036+25E6/(60/16). I will make the second shorter this way. Hi! Can you check the real frequency of the oscillator? If it is too far from 16MHz, there are two options: trim the capacitors that are in the crystal oscillator circuit (I'm not familiarized with the Arduino... but I suppose they will be there), or... software trim changing the counter reload value as you suggest :) Does the counter needs reloading every overflow or it is automatically reloaded? depending on how you are done this, it can also provide some delays that apparently slows the clock. Regards, Javier ___ 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] Clock Correction Algorithm
Hi How about simply adding 1 ms every other second? You could then fine tune it by picking a small number of seconds to not add a ms to. Bob On Nov 24, 2011, at 7:16 AM, Javier Herrero jherr...@hvsistemas.es wrote: El 24/11/2011 13:56, Miguel Gonçalves escribió: Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. That is more than 400ppm error, that sounds quite high. Is the clock frequency of the Arduino so drifted? I would try first to check (and correct a bit) the source of that error. If the crystal frequency is ok, perhaps there is an error in the programming of the timer that generates the timing interrupt. Regards, Javier ___ 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] SDR GPS
On Thu, Nov 24, 2011 at 6:19 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: Has any of you played with this: http://www.sparkfun.com/products/8238 Anyone look at the the one from Parallax that Radio Shack is selling for less than $50? http://www.parallax.com/Store/Sensors/CompassGPS/tabid/173/CategoryID/48/List/0/SortField/0/Level/a/ProductID/644/Default.aspx http://www.radioshack.com/product/index.jsp?productId=12302298 It says it is an antenna, do look at the specs closer. -- http://blog.softwaresafety.net/ http://www.designer-iii.com/ http://www.wearablesmartsensors.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] Symmetricom TimeSource 2700
I wrote: pretty much every BTMon window contains a TOD display. I did a little investigating, and it turns out that the TOD displayed in the BTMon windows is the local system time, NOT time received from the TS2700. Apparently, the TS2700 does not send TOD on the Craft output. Best regards, Charles ___ 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] Clock Correction Algorithm
Hi Atilla!
On 24/11/2011, at 14:42, Attila Kinali att...@kinali.ch wrote:
On Thu, 24 Nov 2011 14:21:37 +
Miguel Gonçalves m...@miguelgoncalves.com wrote:
I am using an Arduino Uno that presumably is running at 16 MHz.
I am using a 16 bit timer with a 256 pre-scaler:
1600 / 256 = 62500 Hz
1 / 62500 = 16 us
65536 - 62500 = 3036
I am setting the counter to 3036 and let it overflow after 65535.
I'm not quite sure i understood you correctly, and i dont know anything
about the arduino and the avr32. But usually, you set a timer to do a
certain repetition rate. Ie raises an interrupt ever x clock cycles.
Or to put it differently, you let the timer run freely, but let it call
you when it's time to do something.
It's really easy: the timer counter is increased 62500 times per second so on
each increase 16 us have passed. I set the start of the counter to 3036 to let
it run to 65535. From 3036 to 65535 one second has passed at the 62500 Hz rate
When it overflows a routine is called that simply updates a global boolean flag.
In my main loop I just have something like
while (true) {
while (!flag) {}
/* a second has passed... this code is executed between seconds */
flag = false;
}
How do you check for the overflow? If you check a flag in your main loop,
this would explain the huge difference, as this polling will add a
(not so) constant delay each time the timer overflows, until you start
your timer again.
I have to check this flag. I do all the processing between seconds. I believe
the interrupt service routine should be kept as short as possible.
Also I checked with a simple counter and the above loop (the inner one) is
executed 48 times per second. I also know that if I don't measure this it
will run much more. Right?
Thanks for your help!
Cheers,
Miguel
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Re: [time-nuts] Clock Correction Algorithm
Hi Javier! On 24/11/2011, at 15:15, Javier Herrero jherr...@hvsistemas.es wrote: El 24/11/2011 15:21, Miguel Gonçalves escribió: I am using an Arduino Uno that presumably is running at 16 MHz. I am using a 16 bit timer with a 256 pre-scaler: 1600 / 256 = 62500 Hz 1 / 62500 = 16 us 65536 - 62500 = 3036 I am setting the counter to 3036 and let it overflow after 65535. If I check the error every second I see the clock getting behind correct time and after 60 seconds it's 25 ms apart from UTC. Perhaps I should increase the initial value from 3036 to 3036+25E6/(60/16). I will make the second shorter this way. Hi! Can you check the real frequency of the oscillator? If it is too far from 16MHz, there are two options: trim the capacitors that are in the crystal oscillator circuit (I'm not familiarized with the Arduino... but I suppose they will be there), or... software trim changing the counter reload value as you suggest :) The software way is probably the best idea as it would account for small differences in different oscillators. I have 3 Arduino boards and will make 3 time displays. Does the counter needs reloading every overflow or it is automatically reloaded? depending on how you are done this, it can also provide some delays that apparently slows the clock. It's manually reloaded with the 3036 value every time the routine is called. If I load it with a bigger value I will make a faster second. If with a small value the second will be longer. Thanks for your help! Cheers, Miguel Regards, Javier ___ 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] Clock Correction Algorithm
Hi! On 24/11/2011, at 15:16, Bob Camp li...@rtty.us wrote: Hi How about simply adding 1 ms every other second? You could then fine tune it by picking a small number of seconds to not add a ms to. An idea but I am searching for a more global and elegant solution. In fact, after reading about PLL (as someone suggested) I noticed that my algorithm is a simple PLL. Cheers, Miguel Bob On Nov 24, 2011, at 7:16 AM, Javier Herrero jherr...@hvsistemas.es wrote: El 24/11/2011 13:56, Miguel Gonçalves escribió: Right! That is what I am doing. The problem is the drift between adjustments. Arduino's clock is slow 25 ms every minute and if temperature changes it will surely be different. That is more than 400ppm error, that sounds quite high. Is the clock frequency of the Arduino so drifted? I would try first to check (and correct a bit) the source of that error. If the crystal frequency is ok, perhaps there is an error in the programming of the timer that generates the timing interrupt. Regards, Javier ___ 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] Clocking a PIC16F628A from a Rubidium Standard
I've done this but don't remember the detail on the wiring. The data sheet made it clear though. One thing I did notice is that the oscillator seemed to power the chip! If I were doing it again I'd probably use some kind of powered buffer on the oscillator input so that when I power down the circuit it actually stops. -Bob On Thu, Nov 24, 2011 at 7:50 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 24 Nov 2011 14:41:24 + Stephen Farthing squir...@gmail.com wrote: I have an Efratom 101 frequency standard with a 10 MHz TTL otput. I want to use this to clock a PIC 16F628A so I can make a frequency counter with a resolution of 1 Hz. I am going to use the design by EI9GQ here http://homepage.eircom.net/~ei9gq/counter.html . What I need to know is how i should go about electronically interfacing the TTL output from the rubidium standard so that it can clock the PIC. Has anyone on the list actually done this successfully? Have a look at the PIC 16F628 data sheet, it will tell you the requirements for the clock input and there should be circuit for external clock signal listed. If it's not in the datasheet, it should be in an appnote. Usually, chips accept sinusoidal and rectangular inputs up to 0V-VDD swing. If i'm reading the schematic correctly and the PIC runs with 5V, then you should be able to just feed the Efratom output directly to the PIC. Maybe, a ceramic 100n capacitor in this line should be used to do a DC isolation (1u cermaic should do as well). Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] SDR GPS
If you want altitude and speed, I recommend the Lassen IQ. ~$25 USD receiver. Good to 18000 meters (59k feet) and 500m/s (1118 MPH). You can exceed any ONE of these specs, but not both. Not really useful for timenuttery though but used often in high altitude balloons. -Bob On Thu, Nov 24, 2011 at 5:04 AM, ehydra ehy...@arcor.de wrote: Pricey, but allows to fly on high-attitude/speed. The region where money ist not so important ;-) - Henry Poul-Henning Kamp schrieb: Has any of you played with this: http://www.sparkfun.com/**products/8238http://www.sparkfun.com/products/8238 -- ehydra.dyndns.info __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Symmetricom TimeSource 2700
Thanks for that information. I had assumed that it was obtained from the cell towers -- after all, my cellphone does show local time. I was hoping that there would be a TOD output. Still the device is very nice and useful as a frequency standard. On 11/24/2011 8:25 AM, Charles P. Steinmetz wrote: I did a little investigating, and it turns out that the TOD displayed in the BTMon windows is the local system time, NOT time received from the TS2700. Apparently, the TS2700 does not send TOD on the Craft output. ___ 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] SDR GPS
Perhaps not in the same league or with the same gee-whiz appeal as a SDR GPS receiver but how about your own DIY GPS receiver: http://dangerousprototypes.com/2011/11/24/homemade-gps-receiver/ and the authors web page: http://www.holmea.demon.co.uk/GPS/Main.htm cheers, Graham ve3gtc -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Robert Darlington Sent: November 24, 2011 11:51 To: ehy...@arcor.de; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] SDR GPS If you want altitude and speed, I recommend the Lassen IQ. ~$25 USD receiver. Good to 18000 meters (59k feet) and 500m/s (1118 MPH). You can exceed any ONE of these specs, but not both. Not really useful for timenuttery though but used often in high altitude balloons. -Bob On Thu, Nov 24, 2011 at 5:04 AM, ehydra ehy...@arcor.de wrote: Pricey, but allows to fly on high-attitude/speed. The region where money ist not so important ;-) - Henry Poul-Henning Kamp schrieb: Has any of you played with this: http://www.sparkfun.com/**products/8238http://www.sparkfun.com/products/8238 -- ehydra.dyndns.info __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] Symmetricom TimeSource 2700
Frederick wrote: Thanks for that information. I had assumed that it was obtained from the cell towers I was hoping that there would be a TOD output. Still the device is very nice and useful as a frequency standard. Symmetricom sold the TS2700 as a Stratum 1 source, so it is likely that TOD information is available from the unit -- my point was just that it does not seem to appear on the Craft output, which is used for monitoring the 2700. p.21 of the manual describes the T1 outputs: The Ensemble Timing Generator provides the timing for the T1 timing signals available at the Output Span A and B connectors in a framed, all-ones format, which is selectable in either D4 or ESF framing. SSM is available with ESF framing. p.21 also describes the 10 MHz output: The Ensemble Timing Generator provides the timing for the 10 MHz low-phase-noise timing signal, available at the 10 MHz Output connector, which can be used for local cellular frequency or testing purposes. It seems clear that Symmetricom does not consider the 10 MHz output to be the TS2700's primary output. Best regards, Charles ___ 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] Differences / Jitter Between Frequency Standard Sources
I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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] Differences / Jitter Between Frequency Standard Sources
Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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] Symmetricom TimeSource 2700
On Nov 24, 2011, at 9:25 AM, Charles P. Steinmetz wrote: I did a little investigating, and it turns out that the TOD displayed in the BTMon windows is the local system time, NOT time received from the TS2700. Apparently, the TS2700 does not send TOD on the Craft output. Hi Charles, When I first used BTMon, I wondered if that was the case. However, reading more about the TL1 messages from the Craft output, there are messages for date and time: date: This parameter is the current date in the 8-digit form -mm-dd, where is year, mm is month (01–12), and dd is day (01–31). time: This parameter is the current time in the 6-digit form hh-mm-ss where hh is hours (0–23), mm is minutes (0–59), and ss is seconds (0–59). The factory setting is GMT for local time. Assuming your investigation is connect, then system time is used in BTMon windows, but it's also documented to be present on the Craft output. For my next investigation, I need to read a bit on RS-422/485 pinouts on a DE-9 connector. I think I have a Maxim sample RS-485 transceiver I can use to look at data on the TOD output. Also, once I know the pinout, I'll know where ground is and can look for a PPS on one of the other pins. If I don't get far there, then I was thinking about looking at the 2 Hz test point and seeing if that's synchronized to a GPS PPS signal. Thanks for information! Kevin ___ 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] Low noise power supplies for time nuts circuitry
78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. Hi Attila, Would you mind recommending some low-noise regulators? Perhaps for both low and high current applications? I'm looking for 12V to power some OXCOs to be used a reference oscillator for a phase noise tester. On the higher current side, maybe to power a rubidium (or at least filter the switcher). Thanks very much, Kevin ___ 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] Low noise power supplies for time nuts circuitry
On Nov 23, 2011, at 5:50 AM, Chuck Forsberg WA7KGX N2469R wrote: How sensitive are each of a Thunderbolt's 3 supplies to noise? This doesn't break down the sensitivities to noise, but Tom shows a range of TBolt output noise for different 3 voltage power supplies: http://www.leapsecond.com/pages/tbolt/noise.htm My suspicion is the -12V is the least sensitive as I heard that it is only used for the RS-232 port. I think either the the +5V which controls the electronics (including things like comparators) and the +12V (which controls the heater to the OXCO) are both noise sensitive. I think the +5V will be the most sensitive. For the PRS10 Rb, two 24V inputs are provided. A higher current for the heater and a lower current for the electronics. To my mind, that makes it likely the electronics (+5V on the TBolt) are the most sensitive. Maybe someone will actually have data to show. Kevin ___ 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] Clock Correction Algorithm
On Nov 24, 2011, at 9:35 AM, Miguel Gonçalves wrote: The software way is probably the best idea as it would account for small differences in different oscillators. I have 3 Arduino boards and will make 3 time displays. For precision timing with a microcontroller, I've been using the 10 MHz from either a TBolt or PRS10 to be the external clock rather than compensating for the frequency offset of a crystal. The disadvantage of this is you need either a GPSDO or a Rb nearby, or cabling to your frequency reference limiting its placement and mobility. Kevin ___ 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] Differences / Jitter Between Frequency Standard Sources
On 11/24/2011 10:01 AM, Robin Kimberley wrote: Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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. actually, any digital display system would be +-1 count in the least significant position. counters, voltmeters, etc. 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] Differences / Jitter Between Frequency Standard Sources
Just as an aside, you /can /get rid of the 'dithering digit' problem if you use a counter which employs a reciprocal counting technique. I use a Thandar Thirlby TF830 locked to a 10MHz reference derived from a Tbolt, but I'm sure there must be others. David Bobbett, G4IRQ On 24/11/2011 18:01, Robin Kimberley wrote: Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ 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] Clocking a PIC16F628A from a Rubidium Standard
On Nov 24, 2011, at 7:50 AM, Attila Kinali wrote: Have a look at the PIC 16F628 data sheet, it will tell you the requirements for the clock input and there should be circuit for external clock signal listed. If it's not in the datasheet, it should be in an appnote. Usually, chips accept sinusoidal and rectangular inputs up to 0V-VDD swing. If i'm reading the schematic correctly and the PIC runs with 5V, then you should be able to just feed the Efratom output directly to the PIC. Maybe, a ceramic 100n capacitor in this line should be used to do a DC isolation (1u cermaic should do as well). Tom's picPET page http://www.leapsecond.com/pic/picpet.htm describes using a TBolt sine directly as a clock source. I'm going something similar with AVRs for an external clock. Since frequency reference sine wave can exceed Vdd, you want to current limit the external clock. For example, an unterminated TBolt puts out 0-7V Pk-Pk. Atmel, in an app note where they hook up the pins of an AVR to 220V mains, states the over/under voltage protection diodes should not carry more than 1 milliamp of current. But, you should both read the datasheet for the output voltage of the Efratom and measure Pk-Pk voltage output at the point of your PIC. To limit to 1 ma for an AVR with a TBolt, you'd want to use a 2K series resistor to drop that extra 2V (7V Pk vs. 5V Vdd) to a milliamp of current. Kevin ___ 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] Low noise power supplies for time nuts circuitry
When you design a regulator, lots of gain is not a criteria in the error amp. (Who needs microvolt accuracy?) High gain generally means two gain stages, which in turn makes it difficult to compensate when driving reactive loads. Thus most op amps are generally a bad idea for an error amp in a regulator. Noise needs to be defined. Generally it means broadband noise. But if your regulator is on the verge of oscillation when the load current or line voltage changes, who cares if the broadband noise is low? This thread is starting to baffle me. Simply dig up a low noise regulator chip. LTC comes to mind. Or troll the net for audiophile shunt designs if you are going to roll your own. What you see done in design often is dubious. Just because it is built, doesn't mean it is good. (Hey, there are doctors that give bad medical advice.) You need to evaluate existing designs for your application. It pays to read the datasheet religiously. Some of these high accuracy regulators can't handle low ESR caps on the output. -Original Message- From: Joe Gwinn joegw...@comcast.net Sender: time-nuts-boun...@febo.com Date: Thu, 24 Nov 2011 10:14:35 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry At 2:28 PM + 11/24/11, time-nuts-requ...@febo.com wrote: Message: 3 Date: Thu, 24 Nov 2011 13:22:38 +0100 From: Attila Kinali att...@kinali.ch To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry Message-ID: 2024132238.0c810b78.att...@kinali.ch Content-Type: text/plain; charset=US-ASCII On Wed, 23 Nov 2011 04:50:49 -0800 Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: How well would a pair of cascaded 3 terminal regulators do - say a 7815 feeding a 7812. 78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. What I see done in low-noise circuits is a low-noise opamp used as a linear voltage regulator to clean up the output of a 78xx or the like regulator. Joe Gwinn ___ 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] Clocking a PIC16F628A from a Rubidium Standard
One thing I did notice is that the oscillator seemed to power the chip! If I were doing it again I'd probably use some kind of powered buffer on the oscillator input so that when I power down the circuit it actually stops. That's a reasonably common problem. Occasionally it's a feature. Most digital inputs have protection diodes from the input pin to VCC and GND. They come for free in most semiconductor technologies. They damp out glitches/reflections. If VCC is open and the circuit isn't drawing a lot of power, you can get enough power from an input signal through the diode to power the whole circuit. It can be nasty to debug if you have something like VCC open to a single chip. The outputs of that chip will be a diode drop lower than the rest of the circuit. I thought about setting up a PIC to make 32 KHz from 10 MHz using power from the 10 MHz input signal but never got around to actually building it. -- It's tricky to safely connect to external signals that may be active when the local power is off. I'm not sure a powered buffer will solve the problem, at least without some more info about what type of buffer you plan to use. In the simple case, you can just insert a big-enough resistor. It needs to be big enough to limit the input current yet small enough not to distort the input signal too much. There are some families of chips made without the protection diodes. The usual application is letting chips running on 3.3V listen to signals from chips running on 5V. (I don't have part numbers handy.) -- 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] Symmetricom TimeSource 2700
Kevin wrote: reading more about the TL1 messages from the Craft output, there are messages for date and time: date: This parameter is the current date in the 8-digit form -mm-dd, where is year, mm is month (0112), and dd is day (0131). time: This parameter is the current time in the 6-digit form hh-mm-ss where hh is hours (023), mm is minutes (059), and ss is seconds (059). The factory setting is GMT for local time. Right. However, the manual does not say that these are sent regularly (every second, or whatever). Note that date and time are both reported as parameters in each Alarm and Event message. So are ocrdat and ocrtm (date and time, respectively, when the event occurred). The Craft output feeds a PC Com port -- I'd think that reading the Com port with a terminal emulator should verify whether the date and time events are sent regularly, or only with Alarms or Events. Best regards, Charles ___ 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] Differences / Jitter Between Frequency Standard Sources
Or modern counters where internally every type of measurement is reduced to a time interval measurement like the HP53132 (150pS resolution). On Thu, Nov 24, 2011 at 8:04 PM, David Bobbett d.bobb...@tiscali.co.ukwrote: Just as an aside, you /can /get rid of the 'dithering digit' problem if you use a counter which employs a reciprocal counting technique. I use a Thandar Thirlby TF830 locked to a 10MHz reference derived from a Tbolt, but I'm sure there must be others. David Bobbett, G4IRQ On 24/11/2011 18:01, Robin Kimberley wrote: Any frequency counter will have an given accuracy +/- the LSD (least significant digit), so alternating between 10.000 and 9.999 looks perfectly normal to me. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Frederick Bray Sent: 24 November 2011 17:56 To: time-nuts@febo.com Subject: [time-nuts] Differences / Jitter Between Frequency Standard Sources I have what would probably be considered to be a newbie question, so please excuse my likely ignorance. I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Thanks for any comments, etc. Fred Bray W6WAW ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Differences / Jitter Between Frequency Standard Sources
Thanks to all who replied. I thought that it was a counter artifact, but I didn't know why. Any suggestions for a reasonably priced good frequency counter that uses the reciprocal method? I saw there were a couple TF830's on ebay, but they were outside the U.S. The HP 5340A looks like it might do the job, but I have heard that there are repair issues if it fails. Thanks. Fred Bray W6WAW ___ 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] Clocking a PIC16F628A from a Rubidium Standard
I have an Efratom 101 frequency standard with a 10 MHz TTL otput. I want to use this to clock a PIC 16F628A so I can make a frequency counter with a resolution of 1 Hz. I am going to use the design by EI9GQ here http:// homepage.eircom.net/~ei9gq/counter.html . What I need to know is how i should go about electronically interfacing the TTL output from the rubidium standard so that it can clock the PIC. Has anyone on the list actually done this successfully? It will probably just work, but you need to read both data sheets to check the details. TTL isn't well defined. It may mean that it's a digital signal rather than a sine wave. It may mean that it's TTL volltage levels rather than CMOS. One common output setup is a strong CMOS driver (typically several sections of a chip in parallel) running on 5V with a series 50 ohm resistor. If the receiving end is terminated with a 50 ohm resistor you will see a 2.5V signal. Without the terminator you will see 5V and overshoot/reflections if the cable is long relative to the rise time. 2.5V is close to the old TTL signal levels. The PIC clock circuitry can run in several modes. (This from memory and I may be forgetting something or confusing it with other chips.) The data sheet or an app note should have the details. One mode is for crystals. It takes 2 pins. Internally, there is an amplifier. There may be a separate mode for slow (low power) crystals such as 32 KHz. There is another mode for an external signal on the clock-in pin. It's intended for things like this. If I was doing something like this, I'd probably start with a 50 ohm input terminator and a 10K resistor over to the clock input pin. Then I'd go check both data sheets to verify that it would work correctly. Do you have a scope? -- 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] Low noise power supplies for time nuts circuitry
The -12V in the TBolt is not used for the serial port. the HIN232 of the TBolt goes from the +5V only, it generates the + and - by the usual switched capacitor technique common to other RS232 interfaces (ADM232, MAX3221 and so on). The -12V powers the LT1014 quad precision opamp that I presume handles the EFC, so care must be taken about the -12 although the PSRR of the opamp comes to the rescue. On Thu, Nov 24, 2011 at 8:25 PM, li...@lazygranch.com wrote: When you design a regulator, lots of gain is not a criteria in the error amp. (Who needs microvolt accuracy?) High gain generally means two gain stages, which in turn makes it difficult to compensate when driving reactive loads. Thus most op amps are generally a bad idea for an error amp in a regulator. Noise needs to be defined. Generally it means broadband noise. But if your regulator is on the verge of oscillation when the load current or line voltage changes, who cares if the broadband noise is low? This thread is starting to baffle me. Simply dig up a low noise regulator chip. LTC comes to mind. Or troll the net for audiophile shunt designs if you are going to roll your own. What you see done in design often is dubious. Just because it is built, doesn't mean it is good. (Hey, there are doctors that give bad medical advice.) You need to evaluate existing designs for your application. It pays to read the datasheet religiously. Some of these high accuracy regulators can't handle low ESR caps on the output. -Original Message- From: Joe Gwinn joegw...@comcast.net Sender: time-nuts-boun...@febo.com Date: Thu, 24 Nov 2011 10:14:35 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry At 2:28 PM + 11/24/11, time-nuts-requ...@febo.com wrote: Message: 3 Date: Thu, 24 Nov 2011 13:22:38 +0100 From: Attila Kinali att...@kinali.ch To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Low noise power supplies for time nuts circuitry Message-ID: 2024132238.0c810b78.att...@kinali.ch Content-Type: text/plain; charset=US-ASCII On Wed, 23 Nov 2011 04:50:49 -0800 Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: How well would a pair of cascaded 3 terminal regulators do - say a 7815 feeding a 7812. 78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. What I see done in low-noise circuits is a low-noise opamp used as a linear voltage regulator to clean up the output of a 78xx or the like regulator. Joe Gwinn ___ 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] Differences / Jitter Between Frequency Standard Sources
On Thu, 24 Nov 2011 12:54:12 -0800, Frederick Bray wrote: Thanks to all who replied. I thought that it was a counter artifact, but I didn't know why. Any suggestions for a reasonably priced good frequency counter that uses the reciprocal method? I saw there were a couple TF830's on ebay, but they were outside the U.S. The HP 5340A looks like it might do the job, but I have heard that there are repair issues if it fails. Thanks. Fred Bray W6WAW Isn't your 5385A counter a reciprocal type ? Quote The Agilent 5385A frequency counter utilizes interpolar-enhanced reciprocal counting http://www.home.agilent.com/agilent/product.jspx? nid=-536902484.536879843.00lc=engcc=US CFO ___ 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] Low noise power supplies for time nuts circuitry - 40μV Adjustable Voltage Regulator Board
Hi All , I find it interesting that this subject came up just as I was looking into cleaning up some of my supplies that power my RB's. Anyway I just bought two of these to play with http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItemitem=130605436528 and they're based on this device... http://www.linear.com/product/LT1764 regards Tim -- VK2XTT :: QF56if :: BMARC :: WIA :: AMSAT-VK :: AMSAT ___ 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] Symmetricom TimeSource 2700
I wrote: The Craft output feeds a PC Com port -- I'd think that reading the Com port with a terminal emulator should verify whether the date and time events are sent regularly, or only with Alarms or Events. I just did this, and the TS2700 has been silent for 30 minutes (it has not had an Alarm or Event since its last power cycle, about 6 months ago, according to its log). I did not want to disturb it by creating an Alarm or Event. However, I tested the terminal emulator by switching the COM port to a TBolt, and confirmed that the TBolt is very chatty. So: I conclude that the TS2700 sends time and date information to the Craft output only as parameters in Alarm and Event messages, not as independent events (at least not more frequently than once in 1/2 hour). Best regards, Charles ___ 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] Differences / Jitter Between Frequency Standard Sources
Looks like my counter is reciprocal. Thanks for the info. Fred Bray W6WAW ___ 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] Symmetricom TimeSource 2700
On Nov 24, 2011, at 2:43 PM, Charles P. Steinmetz wrote: I just did this, and the TS2700 has been silent for 30 minutes (it has not had an Alarm or Event since its last power cycle, about 6 months ago, according to its log). I did not want to disturb it by creating an Alarm or Event. However, I tested the terminal emulator by switching the COM port to a TBolt, and confirmed that the TBolt is very chatty. So: I conclude that the TS2700 sends time and date information to the Craft output only as parameters in Alarm and Event messages, not as independent events (at least not more frequently than once in 1/2 hour). Thanks for the report on that, Charles. I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. Best, Kevin ___ 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] Differences / Jitter Between Frequency Standard Sources
I have a HP 5385A frequency counter, which I am using with an external standard. If I try to compare one 10 MHz standard against another, using one as the external standard and the other as the device being measured, the readout fluctuates between 10.000 and 9.999. This happens when I am comparing a Z3801A and the Trimble look-a-like using the same GPS antenna and identical cables (including length) between the GPS antenna splitter and the two units. I have also used identical cables between the 10 MHz outputs and the counters. Hence, cable variations shouldn't be the issue. The same thing happens comparing the Timesource 2700 against either of the GPS standards. Is this attributable to the different standards or the frequency counter? I haven't yet set up a dual trace scope to compare the various sources directly, but that will be my next step. Fred, This is normal (for both gated and reciprocal counters). Never trust a frequency counter that gives you the same number every time. In fact it is very advantages. If you log hundreds or thousands of these frequency readings and compute the mean you will get a more precise value for your long-term average frequency. It's unlikely you will get a 50/50 split between the two readings; the actual ratio between them allows you to interpolate somewhat between 9 and 0 in the last digit. Try it. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Clocking a PIC16F628A from a Rubidium Standard
Stephen, As well as limiting the input voltage swing into the PIC with a ~2k2 resistor, add an additional 4k7 or 10k resistor (AOT) across the PIC's Vcc rail to ground. This swamps the rectified DC produced by the input drive signal when the PIC DC supply is removed. I've used /tvb's PIC divider in a few projects and experienced the same it's still working phenomenon. Took a while before twigging the input protection diodes were responsible for these unintended consequences. Kit VK2LL On Nov 24, 2011, at 7:50 AM, Attila Kinali wrote: Have a look at the PIC 16F628 data sheet, snip Since frequency reference sine wave can exceed Vdd, you want to current limit the external clock snip To limit to 1 ma for an AVR with a TBolt, you'd want to use a 2K series resistor to drop that extra 2V (7V Pk vs. 5V Vdd) to a milliamp of current. Kevin ___ 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] Low noise power supplies for time nuts circuitry
Hi The Linear LT1764 is reasonably quiet / high current / low dropout. Don't count on getting all three at once. Bob On Nov 24, 2011, at 12:45 PM, Kevin Rosenberg ke...@rosenberg.net wrote: 78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. Hi Attila, Would you mind recommending some low-noise regulators? Perhaps for both low and high current applications? I'm looking for 12V to power some OXCOs to be used a reference oscillator for a phase noise tester. On the higher current side, maybe to power a rubidium (or at least filter the switcher). Thanks very much, Kevin ___ 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] Low noise power supplies for time nuts circuitry - 40μV Adjustable Voltage Regulator Board
The LTC datasheet crows about low current in dropout. Yeah, it's worth crowing about since not all chip use what is called a sat catcher circuit. High current in dropout with PNP pass devices can be a problem. I've seen Micrel regulators that are horrible in dropout. The sat catcher is yet another feedback loop, so it is best to stay out of low dropout if possible. Generally when I buy a LDO, I use the type with a P-fet rather than PNP. I'm not sure if any of these exist with low noise. [I'm usually more concerned with stability.] TI makes good ones. The P-fet pass device doesn't need a sat catcher, so there is one less loop to worry about. Having designed both types, I find the P-fet pass much easier to stabilize. Bipolar devices don't isolated as well as MOS. I'm not familiar with rubycon caps. The low ESR large value caps are organic semiconductor. OSCON is a common brand from Sanyo. Finding the ultimate cap is nearly as much fun as finding the ultimate LDO. Check out Nichicon. Or you can stick with the Rubycon. Glancing at their website, they seem to copy the Nichicon product line. On 11/24/2011 1:37 PM, Tim wrote: Hi All , I find it interesting that this subject came up just as I was looking into cleaning up some of my supplies that power my RB's. Anyway I just bought two of these to play with http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItemitem=130605436528 and they're based on this device... http://www.linear.com/product/LT1764 regards Tim ___ 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] Low noise power supplies for time nuts circuitry
On Nov 24, 2011, at 4:46 PM, Bob Camp wrote: The Linear LT1764 is reasonably quiet / high current / low dropout. Don't count on getting all three at once. Thanks, Bob! Kevin ___ 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] Symmetricom TimeSource 2700
Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ 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] Using Thyme for Stuffed Mushrooms
Stuffed mushrooms are a fine holiday treat. Begin with a box of baby Portabella (Crimini) mushrooms. You know, the ones that start out as spores in a soil of horse manure and hay in a dark, moist limestone cave. The young mushrooms dream of becoming large, but one day the cave is filled with light and men with sharp knives cut them off at the knees. That's what you buy at the store. Clean out the stems and the gills to make room for the stuffing. For ten 5 cm mushrooms, you need 15 to 20 cm of a medium carrot and a stalk of celery, finely chopped. Include some onion if you like; the mushrooms are beyond caring. Sautee them with a clove of finely chopped garlic and add a pinch or two of dried thyme. Cool, then blend with Panko bread crumbs and shredded Parmesan to taste. Stuff the mushrooms and bake at 165 C for 10 minutes, then 3 minutes under the broiler. Make time to enjoy the product with a suitable wine. This is really a great use of your thyme. Oh, wait - this isn't the thyme-nuts list. Never mind. Bill Hawkins The above was intended to entertain. Please don't be offended. ___ 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] DGPS@home
I read that for position accuracy ionospheric effects are the main source for typical single frequency receivers. So looking for DOP would be not helpful because the ionospheric way is for two 'relative' on the same position located teceivers vs. satellites position almost the same and that would cancel this error source out!? The end-effect should be better values than seen in the datasheet. I must ask again. More opinions? - Henry Azelio Boriani schrieb: Usually GPS receivers have DOP figures you can use to estimate the position precision. Maybe worth using timing receivers for position to increase the position accuracy. On Thu, Nov 24, 2011 at 1:01 PM, ehydra ehy...@arcor.de wrote: Hi all! I wonder what would be reasonable location accuracy if two cheap same type GPS modules will be several meters apart? I understand that it involves statistical numbers. Any idea? Say for a small robot. Thanks! - Henry -- ehydra.dyndns.info -- ehydra.dyndns.info ___ 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] DGPS@home
I think the accuracy could be quite good if you took advantage of the times the robot was motionless. During those times it could build up many seconds of averaging and then while moving either use dead reckoning or inertial navigation. On Thu, Nov 24, 2011 at 4:01 AM, ehydra ehy...@arcor.de wrote: Hi all! I wonder what would be reasonable location accuracy if two cheap same type GPS modules will be several meters apart? I understand that it involves statistical numbers. Any idea? Say for a small robot. Thanks! - Henry -- ehydra.dyndns.info ___ 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] Using Thyme for Stuffed Mushrooms
Happy thanksgiving bill - eric Sent from my Banana Jr.(tm) mobile device On Nov 24, 2011, at 8:55 PM, Bill Hawkins b...@iaxs.net wrote: Stuffed mushrooms are a fine holiday treat. Begin with a box of baby Portabella (Crimini) mushrooms. You know, the ones that start out as spores in a soil of horse manure and hay in a dark, moist limestone cave. The young mushrooms dream of becoming large, but one day the cave is filled with light and men with sharp knives cut them off at the knees. That's what you buy at the store. Clean out the stems and the gills to make room for the stuffing. For ten 5 cm mushrooms, you need 15 to 20 cm of a medium carrot and a stalk of celery, finely chopped. Include some onion if you like; the mushrooms are beyond caring. Sautee them with a clove of finely chopped garlic and add a pinch or two of dried thyme. Cool, then blend with Panko bread crumbs and shredded Parmesan to taste. Stuff the mushrooms and bake at 165 C for 10 minutes, then 3 minutes under the broiler. Make time to enjoy the product with a suitable wine. This is really a great use of your thyme. Oh, wait - this isn't the thyme-nuts list. Never mind. Bill Hawkins The above was intended to entertain. Please don't be offended. ___ 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] Low noise power supplies for time nuts circuitry
On Thu, 24 Nov 2011 11:45:05 -0700 Kevin Rosenberg ke...@rosenberg.net wrote: 78xx Regulators are quite noisy. You can use them to filter the noise of a cheap DC/DC converter, but i wouldnt use them feed high precision electronics. There are a lot better designs these days. Would you mind recommending some low-noise regulators? Perhaps for both low and high current applications? I'm looking for 12V to power some OXCOs to be used a reference oscillator for a phase noise tester. On the higher current side, maybe to power a rubidium (or at least filter the switcher). As Bob Camp already said, Linear has some low noise LDO's. Also Ti and Analog are worth a look. All three of them also have a lot of app notes describing how to filter power supply noise for instrumentation and PLL applications. A quick googling revealed the following guides: http://www.ti.com/lit/an/slyt201/slyt201.pdf http://www.designers-guide.org/Design/bypassing.pdf HTH Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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] Clock Correction Algorithm
On Thu, 24 Nov 2011 16:32:04 +
Miguel Gonçalves m...@miguelgoncalves.com wrote:
Hi Atilla!
On 24/11/2011, at 14:42, Attila Kinali att...@kinali.ch wrote:
I'm not quite sure i understood you correctly, and i dont know anything
about the arduino and the avr32. But usually, you set a timer to do a
certain repetition rate. Ie raises an interrupt ever x clock cycles.
Or to put it differently, you let the timer run freely, but let it call
you when it's time to do something.
It's really easy: the timer counter is increased 62500 times per
second so on each increase 16 us have passed. I set the start of the
counter to 3036 to let it run to 65535. From 3036 to 65535 one second
has passed at the 62500 Hz rate When it overflows a routine is called
that simply updates a global boolean flag.
[from another mail]
Does the counter needs reloading every overflow or it is automatically
reloaded? depending on how you are done this, it can also provide some
delays that apparently slows the clock.
It's manually reloaded with the 3036 value every time the routine is called.
If i'm guessing correctly this routine looks something like this:
void timer_routine()
{
flag = true;
load_timer(3036);
start_timer();
}
Then this is the problem. The time until the routine is called is not
zero (due to interrupt latency) and not well defined. Which means,
you get your timer, running for 64k-3036 cycles, then you lose a few
cylcles when the timer_routine is called, and you lose another few cylces
until the timer is started again.
The right way to do it, would be to set the timer into continous mode,
so that it runs freely and raises an interrupt every 64k-3036 cylces.
Then you only have to set the flag in your timer_routine:
void timer_routine()
{
flag = true;
}
This way, the timer is independent of the interrupt latency, and the
latency of the timer_routine.
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
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