Nixies: stupid questions.

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

This ^ !

No problem. Also, 666 posts cowjam. 8)

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 :fearful:

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 :fearful:

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?

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.

wyager: 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.

CowJam: 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...

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

Another question: Ground sharing.

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

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?

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?

In the 74141 there are transistors on each pin... I am waiting for hints too ^_^

My shift register is running with shared ground.

When I say “running” I mean the nixie lights up and changes and the arduino hasn’t caught fire. It isn’t doing what I expected in the slightest though.

Edit: Working properly now. I’d not paid enough attention again. Missed one of the ground pins for the 595 and had hooked the 74141 up to shift register pins 1-4 instead of 0-3.

Time to add a second nixie.

CowJam: Another question: Ground sharing.

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

Yes. Ground must be shared between all circuits, just be sure never to share VCC. I suppose you could, theoretically, make separate circuits with optoisolators, but for what we are doing that makes no sense. I have had no problems sharing ground between all of my circuits, just keep the high voltage separate from low voltage through transistors, driver circuits, whatever.

Edit:oops, didn't see there was another page. Glad you figured it out. As you can see from my schematic (I think I posted that here) I'm just driving a bunch of MPSA42s from a shift register.

Are the Mps42A switching the anode?

Federico: Are the Mps42A switching the anode?

Why do you want to switch the anode?

If you're using 74141s sending an out-of-range command (ie, all four pins HIGH) then the nixie doesn't display anything.

Progress report: I've set up four 74141s and two shift registers (595s), but am running two nixies so far, and a bulb. I'm using a spare PC PSU for power, the arduino is the one I fried so it needs to be powered from USB. I'll be adding a USB plug to the PSU as soon as I've been to maplin to buy a male type B plug.

Here's some pics: Nixies: Click for Big.

The rig (using a bit of Meccano to make a gantry to hold the nixies):

Top view:

At the top is the 12v - 180v PSU. Coming in on the right is a 5v line and a 12v line from the PSU. The breadboard is 74141, 74141 and 595 (in use) and the same again waiting to be hooked up and an IN-35 bulb. The arduino is sat on a bit of polystyrene and attached to the gantry. The nixies are in sockets suspended from the gantry.

CowJam:

Federico:
Are the Mps42A switching the anode?

Why do you want to switch the anode?

I am getting a bit confused.
You guys said that optocouplers are not necessary if I am going to multiplex the nixies.
In your setup aren’t necessary because you hook up the anode and use a 74hc595 with two 74141 for 2 nixies. So if you have 6 nixies you have 3 595 and 6 74141, at least.

But, if you, for example, connect all the cathodes of your nixies together to a single 74141 you need to switch the anodes with the 595, in high voltage multiplexing them and using persistence of vision. I supposed that this was the meaning of the transistor, for dividing the high voltage of the nixies from the low voltage of the IC’s and the arduino…

Fede

I understand, it's my mistake. Sorry for confusing you!

Federico: Are the Mps42A switching the anode?

MPSA42s to switch the cathodes, and MPSA42+MPSA92s to switch the anodes. Look at the bottom of http://sites.google.com/site/willyager/nixie-clock .

Cowjam, I'm glad you've gotten it working. Looking very cool!

Wow, I thought mine was complicated! I've just finished adding the second two nixies, using a breadboard and jumper wires is a nightmare. It's like playing kerplunk in reverse.

I've also added a rotary encoder for changing the numbers.