Re: [time-nuts] GPS for Nixie Clock
Cesium.... this IS time nuts after all... <big grin>
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
On 7/15/2016 8:55 PM, Bob Camp wrote:
Hi
As this is going, it’s not a clock at all. It’s a GPSDO with a Nixie display on it
and now with IRIG timing output.
Do we put an Rb in it or go straight to a Cesium?
Bob
HI
Cesium beam or cesium fountain?
This can go on and on …. :0
Bob
On Jul 15, 2016, at 10:06 PM, Clay Autery cautery@montac.com wrote:
Cesium.... this IS time nuts after all... <big grin>
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
On 7/15/2016 8:55 PM, Bob Camp wrote:
Hi
As this is going, it’s not a clock at all. It’s a GPSDO with a Nixie display on it
and now with IRIG timing output.
Do we put an Rb in it or go straight to a Cesium?
Bob
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
On 7/15/16 5:25 PM, Bob Camp wrote:
Hi
You can do a pretty good job with a high speed photo diode. They are not cheap, but
you can get fast ones if your Visa card is up to it.
The next layer will be that at the relatively low strike voltages normally used, Nixie’s don’t
light up consistently. You either need to compensate for temperature and ambient light / then
calibrate each segment or sense each one as it turns on. Either way … it’s a major learning
experience just to get it into the microseconds range. You can get to nanoseconds, but that
may or may not be possible with conventional Nixie’s.
Preionize the gas with a radioactive source. If it works for Krytrons,
it can work for Nixies. You could also use a pulsed ion source that
turns on slightly before the "top of the second" to irradiate and
prepare the Nixie.
A true time-nut won't let such thing stand in the way of perfection.
Once you have them turned on, you go back through something similar when you turn them
off. It takes a bit of time for all the little gas molecules to go back to rest state. The data I have seen
on that sort of thing suggests a “many microseconds” to millisecond decay process depending
on the gas and how it was driven.
Turning an ionized gas off is always harder than turning it on. Perhaps
a tailbiter type circuit or a negative pulse generator?
Seriously, it does not matter how long it takes to turn a nixie tube
on or off. You measure it and then compensate. Likely would need to
continuously measure and adjust the compensation. This is doable
and is the only hard part of the problem as it is new while the rest
has been done 1000 times.
You'd need some kind of light sensor to measure the tube's response
but you might also connect that sensor to an extra tube that is
hidden. Possible you glue a phototransistor to the face of a nixie
tube then wrap the assembly in light proof black tape. Well this
assumes all the tubes act alike. Perhaps not and perhaps it takes one
number longer than another and you have to measure every cathode on
every tube we don't know and I doubt this data exists.
In any case a nanosecond correct nixie tube would require some kind of
optical feedback loop. and THAT is the engineering chanange
On Fri, Jul 15, 2016 at 8:40 PM, jimlux jimlux@earthlink.net wrote:
On 7/15/16 5:25 PM, Bob Camp wrote:
Hi
You can do a pretty good job with a high speed photo diode. They are not
cheap, but
you can get fast ones if your Visa card is up to it.
The next layer will be that at the relatively low strike voltages normally
used, Nixie’s don’t
light up consistently. You either need to compensate for temperature and
ambient light / then
calibrate each segment or sense each one as it turns on. Either way … it’s
a major learning
experience just to get it into the microseconds range. You can get to
nanoseconds, but that
may or may not be possible with conventional Nixie’s.
Preionize the gas with a radioactive source. If it works for Krytrons, it
can work for Nixies. You could also use a pulsed ion source that turns on
slightly before the "top of the second" to irradiate and prepare the Nixie.
A true time-nut won't let such thing stand in the way of perfection.
Once you have them turned on, you go back through something similar when
you turn them
off. It takes a bit of time for all the little gas molecules to go back to
rest state. The data I have seen
on that sort of thing suggests a “many microseconds” to millisecond decay
process depending
on the gas and how it was driven.
Turning an ionized gas off is always harder than turning it on. Perhaps a
tailbiter type circuit or a negative pulse generator?
time-nuts mailing 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
From: Bob Camp
To get a time resolution of 10 ms (yes 10X 1 ms), you don’t really need the
pps. The timing of
the serial string is probably “good enough”. That assumes you don’t have all
sorts of other
messages turned on as well. In the case of a wall clock, it’s not clear why
anything other
than a basic timing message would be enabled. A sub $10 module likely will
do everything
you need to do.
Bob
I'd second Gary E. Miller's comments. Serial typically isn't good enough
for 10 ms, and may have a significant offset.
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
I, for one, will be following your progress...
I think it would be cool as heck having an ultra-accurate clock with a
Nixie display... It'd be cool to make it flexible enough to output the
time sync to other equipment...
Clay Autery, KY5G
---==========
If you don't mind an LCD display instead of Nixies .....
http://www.satsignal.eu/raspberry-pi/DigitalClock.html
73,
David GM8ARV
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Yes, I was planning on using a high speed photo diode to actually
measure the turn on time of the digits. I hadn't thought of the turn OFF
time, do I want the old digit to be turned off before the new one lights
up or for them to be overlapping? I have been thinking about what
threshold to use, 50% intensity is probably about as good as any other.
It might turn out that different digits turn on differently, so I will
have to calibrate each one separately.
John S.
On 7/15/2016 4:57 PM, Chris Albertson wrote:
If you are going for the sawtooth correction then you also might want
to add some kind of forward correction for the delay in the tubes and
the drivers. Your MOSFET gates the nixie tube itself have capacitance
and switch times that will delay the switch of the display and of
course the digital processing in the FPGA takes some number of
nanoseconds. I think you might need some way to actually measure all
of these as any estimate might be your single largest source of error.
I don't know how to measure it. Perhaps a pair of phototransistors
one aimed at a PPS LED and one at the nixie tube. This unknown delay
is likely larger than the sawtooth correction. at this level you
might have to define when a digital is actually "on" as there is
likely some thermal constant and the numbers don't light up instantly.
I'd bet the turn on time is larger than the sawtooth correction.
What is "on"? 50% brightness?
It gets hard when you start caring about tiny increments of time. I
have a mechanical clock, about 14 inches in diameter that is slaved to
NTP. The designer took a big short cut. Time is kept internally at
the hundreds of microseconds level and the pulse goes off to the
stepper motor at the correct time well at least at the 100+
microsecond level but the hands don't move instantly because (1)
slight gear backlash and (2) they have mass. I can actually SEE the
delay with my eyes. The designer must have forgotten that a "move"
command requires some milliseconds to execute (I'm thinking about
100ms or more). I don't care but it's fun to think the actual display
is 10,000 times less accurate then the internal timekeeping. You
don't want this to happen to happen nixie clock
BTW I did not build my mechanical NTP clock. I got a free broken
clock and had to fix it, cut and soldered a few traces, fixed some
cracked parts and learned how it works in the process.
Finding which PPS to use is easy, you can do that by eye. Compare the
serial data stream to the time on your NTP sync'd computer. A full
second off problem is easy to see.
On Fri, Jul 15, 2016 at 3:53 PM, John Swenson johnswenson1@comcast.net wrote:
Yep, that is theory. The fun part is going to be getting the right edge for
the new PPS. Half the time it will the one before the PPS from the GPS and
half the time it will be the one after. From the sawtooth data I should be
able to figure out which is which to align it to the new LO.
John S.
On 7/15/2016 3:17 PM, Bob Camp wrote:
Hi
If you are going to go “full boat” then you probably should get the
sawtooth correction out of
the GPS and feed that into your control loop. You will need something you
can run out at the
“few hundred seconds” sort of time constant.
Bob
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.
Yes, I was planning on using a high speed photo diode to actually
measure the turn on time of the digits. I hadn't thought of the turn OFF
Or just measure the anode/cathode current of the tube. The plots are non-linear and wonderful.
At this point, consider moving over to the excellent NeoNixie-L group (was yahoo, now googlegroups) for all the rest of your nixie questions. You'll find plenty of digit response time discussions in the archives, as well as hundreds of messages about using WWVB and GPS to set and/or drive the clocks.
Thanks,
/tvb
----- Original Message -----
From: "John Swenson" johnswenson1@comcast.net
To: time-nuts@febo.com
Sent: Saturday, July 16, 2016 12:08 AM
Subject: Re: [time-nuts] GPS for Nixie Clock
Yes, I was planning on using a high speed photo diode to actually
measure the turn on time of the digits. I hadn't thought of the turn OFF
time, do I want the old digit to be turned off before the new one lights
up or for them to be overlapping? I have been thinking about what
threshold to use, 50% intensity is probably about as good as any other.
It might turn out that different digits turn on differently, so I will
have to calibrate each one separately.
John S.
On 7/15/2016 4:57 PM, Chris Albertson wrote:
If you are going for the sawtooth correction then you also might want
to add some kind of forward correction for the delay in the tubes and
the drivers. Your MOSFET gates the nixie tube itself have capacitance
and switch times that will delay the switch of the display and of
course the digital processing in the FPGA takes some number of
nanoseconds. I think you might need some way to actually measure all
of these as any estimate might be your single largest source of error.
I don't know how to measure it. Perhaps a pair of phototransistors
one aimed at a PPS LED and one at the nixie tube. This unknown delay
is likely larger than the sawtooth correction. at this level you
might have to define when a digital is actually "on" as there is
likely some thermal constant and the numbers don't light up instantly.
I'd bet the turn on time is larger than the sawtooth correction.
What is "on"? 50% brightness?
It gets hard when you start caring about tiny increments of time. I
have a mechanical clock, about 14 inches in diameter that is slaved to
NTP. The designer took a big short cut. Time is kept internally at
the hundreds of microseconds level and the pulse goes off to the
stepper motor at the correct time well at least at the 100+
microsecond level but the hands don't move instantly because (1)
slight gear backlash and (2) they have mass. I can actually SEE the
delay with my eyes. The designer must have forgotten that a "move"
command requires some milliseconds to execute (I'm thinking about
100ms or more). I don't care but it's fun to think the actual display
is 10,000 times less accurate then the internal timekeeping. You
don't want this to happen to happen nixie clock
BTW I did not build my mechanical NTP clock. I got a free broken
clock and had to fix it, cut and soldered a few traces, fixed some
cracked parts and learned how it works in the process.
Finding which PPS to use is easy, you can do that by eye. Compare the
serial data stream to the time on your NTP sync'd computer. A full
second off problem is easy to see.
On Fri, Jul 15, 2016 at 3:53 PM, John Swenson johnswenson1@comcast.net wrote:
Yep, that is theory. The fun part is going to be getting the right edge for
the new PPS. Half the time it will the one before the PPS from the GPS and
half the time it will be the one after. From the sawtooth data I should be
able to figure out which is which to align it to the new LO.
John S.
On 7/15/2016 3:17 PM, Bob Camp wrote:
Hi
If you are going to go “full boat” then you probably should get the
sawtooth correction out of
the GPS and feed that into your control loop. You will need something you
can run out at the
“few hundred seconds” sort of time constant.
Bob
time-nuts mailing 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.
Hi
On Jul 15, 2016, at 11:40 PM, jimlux jimlux@earthlink.net wrote:
On 7/15/16 5:25 PM, Bob Camp wrote:
Hi
You can do a pretty good job with a high speed photo diode. They are not cheap, but
you can get fast ones if your Visa card is up to it.
The next layer will be that at the relatively low strike voltages normally used, Nixie’s don’t
light up consistently. You either need to compensate for temperature and ambient light / then
calibrate each segment or sense each one as it turns on. Either way … it’s a major learning
experience just to get it into the microseconds range. You can get to nanoseconds, but that
may or may not be possible with conventional Nixie’s.
Preionize the gas with a radioactive source. If it works for Krytrons, it can work for Nixies.
Your typical Krytron does not get used a lot (limited switching life). A rad stabilized neon bulb is probably
a better thing to compare to. They are more repeatable than a normal bulb. They still drift as they age.
Bob
You could also use a pulsed ion source that turns on slightly before the "top of the second" to irradiate and prepare the Nixie.
A true time-nut won't let such thing stand in the way of perfection.
Once you have them turned on, you go back through something similar when you turn them
off. It takes a bit of time for all the little gas molecules to go back to rest state. The data I have seen
on that sort of thing suggests a “many microseconds” to millisecond decay process depending
on the gas and how it was driven.
Turning an ionized gas off is always harder than turning it on. Perhaps a tailbiter type circuit or a negative pulse generator?
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Holy crap there's a lot of information there... I'll be on that site
for a while!
Thanks!
Clay Autery, KY5G
MONTAC Enterprises
(318) 518-1389
On 7/16/2016 2:06 AM, David J Taylor wrote:
If you don't mind an LCD display instead of Nixies .....
http://www.satsignal.eu/raspberry-pi/DigitalClock.html
73,
David GM8ARV