Nixies: stupid questions.

No problem. Also, 666 posts cowjam. 8)

the number of the beast ]:smiley:

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 ]:smiley:

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. :stuck_out_tongue:

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 :slight_smile:

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.

Wow-lots of wires! Thankfully, the IN-14s I'm using (as soon as USPS feels like delivering them, they've been in the US since at least the 26th) come with long leads, so hopefully it will just be plug-and-play.