[time-nuts] FE5680 GPS Disciplined Controller Update
The response has been very positive such that a $ 45 kit is doable. Working on getting at least two beta tests lined up. However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. I like to float an other idea I did attach a picture of the auxiliary board which we also use on other projects. That board along with inductors and two mini circuit transformers could be added to the kit for an extra $ 8.00. Other parts are readily available. Going forward it would make sense to have a temperature control board and a clean up loop board. We have them but they are express PCB. if members would be willing to do a Gerber version I will gladly work with them off list and than they could be added for an extra $ 4.00 to the kit. We do not have the time. Total kit would be $ 57.00 maybe $ 55.00 including four 5 X 5 cm. boards. Let me know what you think. Bert Kehren In a message dated 6/19/2014 2:56:52 P.M. Eastern Daylight Time, t...@leapsecond.com writes: - Original Message - From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, June 19, 2014 8:31 AM Subject: Re: [time-nuts] FE5680 GPS Disciplined Controller I've been working in the same thing BUT I don't want anyone who builds it to need a PCB. And I want the firmware to load over USB so there is no need to ship programmed chips or deal with external programmers. I think I can get the cost below $20. That said I doubt I'll get 1E-13 performance out of my Rb. My little Arduino based controller has been running now for a couple months and keeping a crystal in lock. The board has a pins left over for a serial port that I'll hook up to the Rb. The trick to getting the cost down is NOT to do a custom PCB. Take advantage of one of the uP development boards and then for under $5 you get the USB interface, D/A and A/D, serial ports, timers and quite a bit of logic all 1/3rd the size of a credit card. On Thu, Jun 19, 2014 at 12:57 AM, Jan Boutsen jan.bout...@telenet.be wrote: Count me in for an assembled and tested board. Great project. Jan - Original Message - From: ewkeh...@aol.com To: time-nuts@febo.com Sent: Wednesday, June 18, 2014 8:49 PM Subject: [time-nuts] FE5680 GPS Disciplined Controller FE5680 GPS Disciplined Controller With all the FE 5680 rubidium oscillators being used as door stops out there some of us decided to develop a GPSDO for it. The main question we have: Is there sufficient interest among time nuts for a discipline controller for the FE5680 to make it available? Looking at the postings over the last two years I am not so sure. The construction and preliminary testing of a Brooks Shera style GPS discipline controller for the later version (6.81e-13 resolution) of the FE5680 has been completed. We are trying to determine the number of people that would be interested in obtaining an FE5680 discipline controller (if there is sufficient interest about $45 a kit shipping included, $75 for an assembled and tested board, international orders for an additional $5) when it is released. We are also looking for three Beta testers that would be willing to purchase, assemble, and test our Beta release controller kit with their own FE5680A and GPS receiver or Tbolt and provide feedback. Please send an email to _EWKehren@aol.com_ (mailto:ewkeh...@aol.com) Subject Time-Nuts FE 5680A, if you would be interested in being one of the three Beta testers. A key requirement is the willingness to get to it right away, the board assembly takes about 30 minutes. Instrumentation to measure results is also a requirement. We obtained impressive results using a cheap ublox 6M receiver. The FE5680 GPS discipline controller is a small (2” x 2”) board using 8 DIP’s and 1 SOT23-5 package powered by +5v with 0.1” headers for all inputs and outputs. Our plan is to have the kit supplier solder in the only SMD device on the board. A GPS receiver 1PPS and 10 MHz sine from the FE5680 feed the board with two 9600 baud serial ports sending TTL level tuning commands to the FE5680 and receiving commands from and sending status data to a PC for data logging and system control via a simple terminal program. In the chip count are two opto couplers that allow the use of isolated TTL to USB conversion. These USB adapters are readily available and furnish the 5 V necessary for the secondary of the opto circuit. An option is to not use the
Re: [time-nuts] FE5680 GPS Disciplined Controller Update
However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. Can you clarify the two orders of magnitude claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report. I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 1 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover. Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference? /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.
Re: [time-nuts] FE5680 GPS Disciplined Controller Update
Tom, airflow, or changes in airflow are typically much worse for ADEV than actual ambient temperature changes in still air. In still air for example a typical Eurocan DOCXO will have a case temp of about 55C to 60C at 25C ambient. Turn on any kind of significant airflow over that part and the air temperature will be nearly the same as before, but the case of the DOCXO is now very quickly cooled to 30C to 40C by the airflow. This affects mostly TCXO and single-oven units (including Rb's etc), it does very little to DOCXO units typically because the outer oven takes the brunt of the temp change and insulates the inner oven. There are other components on the PCB though next to the DOCXO that will be affected such as the DAC, DAC reference, EFC filters, current ground loops due to changing heater-current on the ground pin, etc. This even affects TCXO's because they are typically heated by themselves and other components on the PCB, and any kind of airflow change will cause an instant temp change on the TCXO due to cooling. So in my opinion a bang-bang controlled fan near any kind of oscillator is about the worst thing one can do for short term stability. bye, Said In a message dated 6/24/2014 13:35:21 Pacific Daylight Time, t...@leapsecond.com writes: However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. Can you clarify the two orders of magnitude claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report. I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 1 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover. Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference? /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 mailing 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] FE5680 GPS Disciplined Controller Update
bang-bang servos do depend on inherent low-pass filtering by the controlled device. Don saidj...@aol.com Tom, airflow, or changes in airflow are typically much worse for ADEV than actual ambient temperature changes in still air. In still air for example a typical Eurocan DOCXO will have a case temp of about 55C to 60C at 25C ambient. Turn on any kind of significant airflow over that part and the air temperature will be nearly the same as before, but the case of the DOCXO is now very quickly cooled to 30C to 40C by the airflow. This affects mostly TCXO and single-oven units (including Rb's etc), it does very little to DOCXO units typically because the outer oven takes the brunt of the temp change and insulates the inner oven. There are other components on the PCB though next to the DOCXO that will be affected such as the DAC, DAC reference, EFC filters, current ground loops due to changing heater-current on the ground pin, etc. This even affects TCXO's because they are typically heated by themselves and other components on the PCB, and any kind of airflow change will cause an instant temp change on the TCXO due to cooling. So in my opinion a bang-bang controlled fan near any kind of oscillator is about the worst thing one can do for short term stability. bye, Said In a message dated 6/24/2014 13:35:21 Pacific Daylight Time, t...@leapsecond.com writes: However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. Can you clarify the two orders of magnitude claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report. I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 1 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover. Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference? /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 mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- The power of accurate observation is commonly called cynicism by those who have not got it. -George Bernard Shaw Dr. Don Latham AJ7LL Six Mile Systems LLC 17850 Six Mile Road Huson, MT, 59846 mail: POBox 404 Frenchtown MT 59834-0404 VOX 406-626-4304 Skype: buffler2 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.
[time-nuts] FE5680 GPS Disciplined Controller Update
Check out the temperature control code in Lady Heather. It uses a nice PID controller algorithm (from Warren Sarkison) to PWM modulate a fan to stabilize the environment around the Tbolt. It can achieve millidegree range stability... I have seen long term RMS values of the temperature plot less than a few micro-degrees. The standard Tbolt oscillator has a rather horrible tempco... I'll post some recommendations/findings about various environmental sensors I tried while I was building my weather/envionmental sensor package. Hint: the MS5611 pressure sensor chip is very nice. Has 24 bit ADCs for the pressure and temperature readings and produces very stable readings with a 100 Hz update rate. -- However it is disappointing that no one has stepped up to tackle the temperature problem. ___ time-nuts mailing 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] FE5680 GPS Disciplined Controller Update
On Tue, Jun 24, 2014 at 3:24 PM, Mark Sims hol...@hotmail.com wrote: ... However it is disappointing that no one has stepped up to tackle the temperature problem. I can post what I have. It's a uP based PWM fan controller. It is a stand alone device that does not know anything about the FE5680 but it would be easy to add into any GPSDO using the GPSDO's existing uP provided there were enough extra analog pins available. It uses the Arduino software environment but I built it using a bare 8-pin DIP. The problem with it is I do not have a good temperature sensor, The ones I tried are noisy. SO I'm looking forward to your sensor info. My first controller used a comparator chip. Then I figured the uP was the same cost and same 8-pin package but could do things like PID, data logging, led status blinking and whatever. This is a start on the code that works just like the comparator and uses a pot for the user to adjust a set point. If you see a way to make this better post the changes. Some things I will do are (1) use better sensor, (2) use PID library, (3) measure ambient air temp. FanController.ino https://dl.dropboxusercontent.com/u/28915695/FanController.ino BTW is there any design info on the FE5680 controller. Schematics of source code? -- 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] FE5680 GPS Disciplined Controller Update
Again we are talking past each other I am talking about temperature compensation with the DDS that ideally should be removed. Those steps upset any loop. Bert In a message dated 6/24/2014 6:38:48 P.M. Eastern Daylight Time, hol...@hotmail.com writes: Check out the temperature control code in Lady Heather. It uses a nice PID controller algorithm (from Warren Sarkison) to PWM modulate a fan to stabilize the environment around the Tbolt. It can achieve millidegree range stability... I have seen long term RMS values of the temperature plot less than a few micro-degrees. The standard Tbolt oscillator has a rather horrible tempco... I'll post some recommendations/findings about various environmental sensors I tried while I was building my weather/envionmental sensor package. Hint: the MS5611 pressure sensor chip is very nice. Has 24 bit ADCs for the pressure and temperature readings and produces very stable readings with a 100 Hz update rate. -- However it is disappointing that no one has stepped up to tackle the temperature problem. ___ time-nuts mailing 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] FE5680 GPS Disciplined Controller Update
Hi If: 1) You are after better than 1.0 x 10^-13 accuracy 2) You are getting 1 to 9x10^-9 at one second ADEV out of your GPS 3) You have a telecom Rb with 1 to 5x10^-10 temp coef over a 70C delta 4) Your Rb self heats 20 to 30C in still air Here’s some math: You will need at least 10,000 seconds to get a single frequency estimate and likely 100,000 seconds. You are likely to go through temp cycles in a room at a 30 to 90 minute rate. (1800 to 3600 sec). Your room temp swings are *way* outside your likely loop. The Rb will have to deal with them by it’s self. —— Your Rb is “sort of” compensated in the temcom units. It’s more like a TCXO than an OCXO. 1x10^-10 over 50C would give you 2x10^-12 per degree C. That may be better or worse than the sample you have. The “worse” really comes in when you have one that’s a parabola or third order temp curve. At least around here a room swing of 2 to 4 C is pretty normal with the heat or air-conditioning turned on. That gets you into the 4 to 8x10^-12 swing range. In a typical garage you are at 10C and 2x10^-11. If you want that to be *below* your 1x10^-13 goal, you have to knock it down by about 100X. —— Is the goal rational? Well this is Time Nuts …. It is roughly the sort of goal Bert has said they are after. Most of the lightweight Rb’s have a major ADEV hump when the temperature compensation cuts in. Without *good* temperature stabilization, you will not disable this correction. There’s no real way to know what the ADEV is without this hunting until you do it. Because of the self heating (and gradients), it’s not a real easy thing to do. If you are using an ensemble of parts to get the ADEV, temperature likely will correlate between them. You will not get the “group vote” to suppress it the way you some other sources of ADEV. —— Yes, I’m sure Bert can cross the T’s and dot the i’s better than I can, but that’s a pretty good outline of the problem. Bob On Jun 24, 2014, at 4:34 PM, Tom Van Baak t...@leapsecond.com wrote: However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. Can you clarify the two orders of magnitude claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report. I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 1 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover. Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference? /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 mailing 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] FE5680 GPS Disciplined Controller Update
Lets be clear the 1 E-13 is a totally different project and does not relate to the FE 5680 A. Yes most likely we will use the same universal controller but with different code, same board. GPS crosses the 1 E-13 line at 10 seconds little more than a day. I whish it was just temperature as I mentioned we are able to hold the back plate of a FRK at 0.01 C. But that is the easy part. Bert Kehren In a message dated 6/24/2014 8:06:52 P.M. Eastern Daylight Time, kb...@n1k.org writes: Hi If: 1) You are after better than 1.0 x 10^-13 accuracy 2) You are getting 1 to 9x10^-9 at one second ADEV out of your GPS 3) You have a telecom Rb with 1 to 5x10^-10 temp coef over a 70C delta 4) Your Rb self heats 20 to 30C in still air Here’s some math: You will need at least 10,000 seconds to get a single frequency estimate and likely 100,000 seconds. You are likely to go through temp cycles in a room at a 30 to 90 minute rate. (1800 to 3600 sec). Your room temp swings are *way* outside your likely loop. The Rb will have to deal with them by it’s self. —— Your Rb is “sort of” compensated in the temcom units. It’s more like a TCXO than an OCXO. 1x10^-10 over 50C would give you 2x10^-12 per degree C. That may be better or worse than the sample you have. The “worse” really comes in when you have one that’s a parabola or third order temp curve. At least around here a room swing of 2 to 4 C is pretty normal with the heat or air-conditioning turned on. That gets you into the 4 to 8x10^-12 swing range. In a typical garage you are at 10C and 2x10^-11. If you want that to be *below* your 1x10^-13 goal, you have to knock it down by about 100X. —— Is the goal rational? Well this is Time Nuts …. It is roughly the sort of goal Bert has said they are after. Most of the lightweight Rb’s have a major ADEV hump when the temperature compensation cuts in. Without *good* temperature stabilization, you will not disable this correction. There’s no real way to know what the ADEV is without this hunting until you do it. Because of the self heating (and gradients), it’s not a real easy thing to do. If you are using an ensemble of parts to get the ADEV, temperature likely will correlate between them. You will not get the “group vote” to suppress it the way you some other sources of ADEV. —— Yes, I’m sure Bert can cross the T’s and dot the i’s better than I can, but that’s a pretty good outline of the problem. Bob On Jun 24, 2014, at 4:34 PM, Tom Van Baak t...@leapsecond.com wrote: However it is disappointing that no one has stepped up to tackle the temperature problem. how many have looked at the temperature attachment and clicked on the N5TNL link. Let me make it clear that yes the GPSDO will work but there will be one or two orders of magnitude degradation without active fan temperature control unless the internal temperature compensation is disabled. Can you clarify the two orders of magnitude claim? That's hard for me to believe, I think, without seeing the ADEV plots or actual lab report. I mean, even a cheap XO or TCXO or OCXO can be disciplined against GPS and achieve superb results. Temperature (or rather, temperature rate of change) has little effect short-term. Temperature also has little to zero effect long-term. So it's only in the, what, tau 100 to 1000 or maybe 1 second range that temperature even matters. As long as the LO is locked to GPS; I assume you're not talking about holdover. Obviously you'd want a slightly shorter loop time constant for a non-temperature-controlled Rb than a fancy temperature-controlled Rb. But does this really make a one or two *orders of magnitude* difference? /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 mailing 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.
