Flickering on Wemos Nixie display (IN-12 tubes.)

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2 months 1 day ago #11304 by BobM
I've just finished building a 4-digit Wemos clock using IN-12 nixies. The clocks work well - almost. There is an annoying flicker which appears randomly. The nixies never extinguish, but their brightness alters slightly for a fraction of a second. All tubes are affected.

My first thought was that there is an HT problem so I've changed both the inductor and C13. No improvement.. Additionally, I've checked for dry joints around the HT circuit.

There does appear to be some noise on the HT line but I'm not sure if this is normal given the method being used to generate the 170 volts.

Any suggestions gratefully received.

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2 months 1 day ago #11308 by Ty_Eeberfest
This is definitely one for Ian to answer. But let's clarify a few things:

1) When the brightness alters does it always decrease momentarily or does it increase sometimes?

2) Do you have the Use LDR option turned on in the configuration? If so turn it off and let us know if the problem changes or goes away.

3) Is it truly random or is the time between "glitches" somewhat consistent?

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

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2 months 1 day ago #11310 by BobM
Many thanks for taking the time to reply. In answer to your questions:-

1) It's surprisingly hard to tell, but I'm almost certain that the displays are dimming fractionally.
2) Turning off the LDR makes no difference to the problem.

3) The glitches seam to appear at random.

Could this be a multiplexing issue? The reason I ask is this. I've been looking at the waveform on pin 3 of the opt-isolators. Running my scope on a fairly slow time base (100ms/div) I can see distinct, apparently random, glitches. I assume that these glitches might cause a flicker in the nixie brightness. Incidently, I'm making these observations with the LDR turned off.

Thanks again for your help.

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2 months 1 day ago - 2 months 1 day ago #11311 by BobM
Duplicate post - removed by author.
Last edit: 2 months 1 day ago by BobM. Reason: Duplicate post

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2 months 1 day ago #11312 by Ty_Eeberfest
Thanks for that info. Please try putting the scope on Pin 1 instead of Pin 3 of the opto and see if you still can see the glitch. Reading Pin 3 (high voltage side) of the opto doesn't distinguish between a glitch in the multiplexing or a glitch in the HV supply. Reading Pin 1 (low side) takes the HV supply out of the equation and just shows what the multiplex signal is doing.

Also, are you pretty confident that the glitches you see on your scope coincide with the glitches you see on the tubes?

I tend to agree that multiplexing is the likely culprit considering that the HV supply is essentially a "stand alone unit" that typically either works fine or doesn't work at all. But lets see what you find on Pin 1 of the optos.

Might as well ask now: are you sure you have the latest firmware running on your Wemos? Running version can be seen on the Status page, current version is 4. Updated firmware, if needed, is here:
www.nixieclock.biz/Downloads/4-Digit-ESP-Firmware-V4.zip

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

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2 months 23 hours ago - 2 months 10 hours ago #11313 by BobM
Thanks again for the reply. The glitches are present on pin 1 of the opto-isolators.

With regard to the firmware, yes I am using version 4.

Picture of scope screen looking at pin1 attached. All pin 1s display similar results. All I can safely say at the moment is that when there is no flickering on the display there are no glitches showing up on the scope.

Attachments:
Last edit: 2 months 10 hours ago by Ty_Eeberfest. Reason: Put the image inline

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