[time-nuts] GPS for Nixie Clock

Bob Camp kb8tq at n1k.org
Sat Jul 16 08:41:36 EDT 2016


Hi


> On Jul 15, 2016, at 11:40 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.

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?
> 
> 
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