Digit Brightness, Classic Rev6, IN-8 Tubes

I agree Jim, a short video could well help. Maybe there's just something that is getting lost on the way.

And Jedidiah, do you really have to wear those welding goggles indoors?

On one hand brightness is indeed subjective. On the other hand this isn’t his first clock. www.tubeclockdb.com/forum/12-arduino-nix...-wi-fi-not-available

A video of normal operation AND a video of healing mode are what I’m wishing for at the moment.

Those pictures are fake! Nobody keeps their bench that clean.

Kidding.

But seriously, those are pictures of an UNO All In One shield but per the thread title I've been under the impression the whole time that we were dealing with a Classic Rev 6. It shouldn't make much difference, but still... what's up?

This is not a software issue. I promise. If the software was defective why wouldn't there be a whole bunch of people complaining of dim displays? And why aren't my own clocks dim? Your waveforms and voltages are pretty much the same as mine and my clock isn't (to my eye at least) dim. If your software and mine were acting different the waveforms / timing should differ.

I've been testing a few things. Based on how my clock behaves I don't agree that changing the anode resistor to 1.5K does nothing. I rigged something with a switch so I can switch one tube between 3K and 1.5K quickly and I see a very definite increase of brightness at 1.5K. The tube that's on 1.5K is is visibly brighter than its neighbors. It's not glaringly brighter but it is definitely brighter.

You won't ever get a full 2.5mA thru the tubes. 2.5 * 6 = 15mA (the pulse current needed to give a tube 2,5mA avg) which is slightly more than the optos can source. IOW if you replaced the 3K with a wire jumper either the opto would limit to ~14mA or the opto would fry - not sure which. I'm basing this statement on what Ian told us about the optos HERE

At this point I'm kinda stuck. Hopefully Ian or Jim will come up with something I haven't thought of. Or maybe Torsten will drop by and offer his opinion. I've been over and over that drive circuit and I can't see any way changing an anode resistor would not change brightness, at least a little bit. That's just plain weird,

IAN - Why am I seeing ~60VDC on the anodes that are "off"? Verified my reading using healing mode so this is not a MUX / meter artifact. Is this because the EL817s are operating above collector-emitter breakdown voltage? It doesn't seem to affect anything but I'm curious about the unexpected voltage.

Oh BTW, those app notes I linked yesterday show some characteristic curves for some Burroughs Nixies. Shouldn't be drastically different from Russian tubes. The curves seem to show that a Nixie is not a purely resistive device. Its apparent resistance varies depending on voltage or current so in effect we are chasing moving targets. This helps explain some of the weirdness we are seeing... the tubes apparently behave in a somewhat non-linear manner.

Or IOW - a 10% change (for example) in anode resistor doesn't necessarily produce a 10% change on current or brightness.