[time-nuts] GPS for Nixie Clock

Chris Albertson albertson.chris at gmail.com
Sat Jul 16 01:04:54 EDT 2016

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 at 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?
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Chris Albertson
Redondo Beach, California

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