Suggestions for debugging a dead nixie (Wemos 4 digit clock)

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4 months 1 week ago #11602 by Ian
I wonder what they are really meant for? Are they "spark gap" in the sense of "electrical overvoltage protection"?

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4 months 1 week ago #11604 by Duane
Ian,
That is exactly right. I originally bought them to use in my solar powered telescope observatory. I was having some trouble with lightning and static induced faults in the electronics. I had the positive and negative cables from the solar panels running underground to the observatory. At the observatory end, I placed a spark gap device from each power line to ground (which was a copper rod driven into the ground.

The idea was that normally, the devices did not conduct and had no effect on the power. If a nearby lightning strike occurred and induced a high voltage spike on one or both of the power leads, the devices would start to conduct at 200v and limit the spike getting into the electronics by shunting the spike to ground.

After the spark gaps, and at the electronics I had MOVs and other ESD protection to handle the remaining lower voltage spike.

I am not sure if they are any better than just using neon bulbs like a NE2. One issue is that these devices conducted at 200v, so worked well for the US 115v power lines, where neon bulbs would already be conducting. I guess if you put 2 or 3 NE2s in series it might work as well.

Conversely, there might be some interesting application of these devices replacing NE2s in circuits like marx high voltage generators or some other neon bulb based thing.

Not sure if they ever really worked, as I was never using the telescopes during a lightning storm :), but I always thought it would be cool to see them sparking and glowing during a storm. Sort of a mini-Frankenstein lab!

- Bill

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4 months 1 week ago #11606 by Duane
Ian and Ty,
I just wanted to let you know that after replacing the bad Nixie, and replacing the spark-gap devices with neon bulbs, the clock is running great. Thanks to both of you for your help.

I am getting some flickering of the lower neon bulb, so will probably try replacing that bulb to see if the problem goes away.

I really like the on-board ESP8266 web server for managing the clock. It is really a great merge of old and new in one device.

- Bill

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4 months 6 days ago #11608 by Ty_Eeberfest
Thanks for following up. Good to know it's working.

If the neons persist in flickering you might consider changing the series resistors to slightly lower values. I'm of the opinion there's no one size fits all resistor value since the characteristics of neon bulbs vary. Trial and error may be your best bet.

Look into it later when the dust is clearing off the crater.

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3 months 2 days ago #11767 by Duane
Hi Ty,
Just wanted to let you know your suggestion worked. I dropped R10 and R12 from 220K to 180K and the flickering is gone.

Thanks, - Bill
The following user(s) said Thank You: Ty_Eeberfest

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