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Topic: Nixies: stupid questions. (Read 9495 times) previous topic - next topic

CowJam

I googled for it.  Not sure I had a datasheet for my actual nixies, but I got the datasheet for the chips (which came with the nixies) by googling, and this is it: http://cowjam.co.uk/arct/k155id1.pdf

I've got some IN-35s which are just neon bulbs and they run fine at 180v (or whatever my circuit is running at) and ran fine with or without a 33k ohm resistor.
These ones: http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=390206146006&ssPageName=STRK:MEWNX:IT#ht_864wt_905

Federico

We bought nixies from the same vendor :-)
Mine are those
http://cgi.ebay.it/ws/eBayISAPI.dll?ViewItem&item=400174245756&ssPageName=STRK:MEWNX:IT
I am going to try to drive them at 170v and see...
After reading about your experience I was thinking that multiplexing and optocouplers should be the safest way...
Federico - Sideralis
Arduino &C: http://www.sideralis.org
Foto: http://blackman.amicofigo.com

CowJam

Yeah, optocouplers are the way to go! 

If I figure out what happened I'll report back on here.

wyager

#18
Jan 29, 2011, 08:31 pm Last Edit: Jan 29, 2011, 08:34 pm by wyager Reason: 1
BTW guys, small neon bulbs should have at least 100K resistors (some use 200K) at 170+V or else they could burn out themselves or your circuit. I am able to multiplex them at 170v with a 100K resistor. Remember that the gas inside them will change its resistance until the voltage across the lamp is the sustaining voltage. A 200K resistor (which is probably better for long life) makes them look a little sputtery.

My A1As regulate themselves at 60V, which means that 110V gets dropped over the anode resistor. 110V/100000?=1.1mA. Almost twice the recommended amount, but I figure since I'm multiplexing... Still probably not healthy.

Federico

wyager, thanks a lot for the advice. I am going to follow it!
Federico - Sideralis
Arduino &C: http://www.sideralis.org
Foto: http://blackman.amicofigo.com

CowJam


wyager, thanks a lot for the advice. I am going to follow it!


This ^ !

wyager

No problem. Also, 666 posts cowjam.  8)

Federico

the number of the beast  ]:D

By the way i see that you (wyager) use a lot of transistors for driving your project. Don't you have a 74141 off hand?

ps. the optocouples i need, TLP627, are damn expensive  :smiley-eek-blue:
Federico - Sideralis
Arduino &C: http://www.sideralis.org
Foto: http://blackman.amicofigo.com

wyager


the number of the beast  ]:D

By the way i see that you (wyager) use a lot of transistors for driving your project. Don't you have a 74141 off hand?

ps. the optocouples i need, TLP627, are damn expensive  :smiley-eek-blue:


I was basing my project off parts I could get from digikey and I couldn't find any HV nixie drivers. The MPSA42s were only like 5 bucks for 25 IIRC, so I just went with those. I suppose after the shift registers and resistors and perfboard, the 74141s off ebay would have been cheaper, but it was a learning experience anyway.  :P

BTW, are the optocouples to protect the rest of the circuit from high voltage?

CowJam

I don't know if this will have contributed to the burnout, but I have discovered that I'd got the pins all muddled.

The power and ground pins were fine, but I had misinterpreted the position of the nixie pins so that I had the number sequence reversed.

I had also failed to spot the utterly confusing layout of the logic pins on the IC.  If you look you'll see that the pins are labelled A, D, B, C (in that order).  The logic chart is labelled D, C, B, A. 

I will have undoubtedly sent things to the IC that it wasn't expecting, though the logic chart says that should merely have resulted in no output.

Federico


BTW, are the optocouples to protect the rest of the circuit from high voltage?


I need them for multiplexing the nixies. If I connect all the cathodes to the nixie driver IC then I need a way to switch on the 170v anodes. I am experimenting the tlc5940 but I can't let it manage the high voltage. That's way I tought about optocouplers connected to the high voltage anche my TLC to open and close the gate.


I had also failed to spot the utterly confusing layout of the logic pins on the IC.  If you look you'll see that the pins are labelled A, D, B, C (in that order).  The logic chart is labelled D, C, B, A. 

So the datasheed is wrong?? Anyway it looks like a strange way for burning an IC...
Federico - Sideralis
Arduino &C: http://www.sideralis.org
Foto: http://blackman.amicofigo.com

CowJam

No, the datasheet is fine. I hadn't read it properly.

CowJam

Another question: Ground sharing.

Do I share the ground for the 180v and 5v circuits?

Federico

Just in time, I was going to ask the same question. I think that no, for what I can understand for driving for example the neon bulbs you have to ground them to the arduino with the high voltage mpsa42 transistor, right?
Federico - Sideralis
Arduino &C: http://www.sideralis.org
Foto: http://blackman.amicofigo.com

CowJam

I hope someone answers soon, I'm about to run another set up (using a shift register) and I don't to kill anything else.

Thing is, the 74141 has one ground pin and runs 5v and high volt so that must share a ground, right?

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