[time-nuts] GPS for Nixie Clock
jimlux at earthlink.net
Fri Jul 15 23:40:20 EDT 2016
On 7/15/16 5:25 PM, Bob Camp wrote:
> 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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