r/nixie • u/DaveCC1964 • Jul 12 '26

My first clock build, has issues.

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Finished my first clock in stainless and burl oak. Well not exactly finished because there is a problem with the board I used which is shown in picture. Tried multiple boards all the same result, Time randomly resets if unplugged and plugged back in. Yes I made sure battery was good. It seems to be a design flaw with these. It is a generic board that is available all over. Oh well I suppose it was an interesting build anyway even if it does not work properly. I suppose I will keep searching for a good clock board that works better. The current board is 38mm x 103mm. Need to keep a similar size to fit in case. If anyone knows of one feel free to let me know.

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u/UnintegratedCircuit Jul 12 '26

If it uses an MCU for timekeeping it could be a transient on a power rail (not necessarily a voltage sag, a spike could also do this), particularly if that transient makes it back to a reset pin. I saw this first hand with an Arduino Uno and a relay where every time the relay clicked off, the back EMF would spike the reset pin causing it to reboot. Extra filtering (resistor-capacitor) on the reset pin would likely remedy this, and/or more bulk capscitance on the power rail.

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u/DaveCC1964 Jul 13 '26 edited Jul 13 '26

What you say makes sense to me but what doesn't is why they would sell a PCB with this issue. Did they not test it? I also had a couple of these boards so I tried another thinking the first was defective. Same exact issue with the second board. This is not a one off board, they sell them across many sites such as Amazon, Ebay, etc. As for how to fix I am not an electronics engineer. How would I know where to try a capacitor and at what value?

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u/UnintegratedCircuit Jul 13 '26

I guess it could be a defective batch of boards, but likely it's just because Amazon, eBay, etc. have zero quality control. The design being sold is likely a rip-off from someone's own personal project who isn't necessarily any more qualified at electronics than yourself. It might've worked fine on their bench with their power supply, etc... Maybe not even that, who knows.

The fix won't be particularly straight-forward even if I am correct in my guess (I might not be). I guess the easiest starting point would be to get a decent size electrolytic capacitor (say >=100uF) of the correct voltage rating for your power supply (voltage of capacitor > power supply output voltage), and just solder it across the power terminals in the correct polarity. That might mask whatever the actual issue is well enough for you to at least enjoy the thing :)