# Using Nixie tubes as a part of a logic clock?

#### Rocky_circuits

Joined Nov 1, 2011
57

For my intro to electronics class I have to make a clock using a logic circuit. I'm sure some of you have seen posts about it before, it appears to be a common project for early electrical engineer students.

While I may need help with the circuit in the future, my first question is more of how to make a much more exciting logic clock using Nixie Tubes instead of boring old 7-segment displays. There are a ton of nixie tubes I've been looking at, I can't quite seem to find which one would be the best looking.. If you happen to have any suggestions on what you personally would think would look the best I would love to know Preferrably between 10-20 dollars per tube. They have gotten expensive!
I found this site but it's half german. Atleast it gives me a good list of possible tubes: http://www.tube-tester.com/sites/nixie/trade01-nixie-tubes.htm

So now there real question: How does one go about setting up one of these tubes compared to a simple 7segment LED. Primarily because VFD (vacuum flourescent displays) use much more voltage (around 60v's). Nixies take about 170 volts.. Which I'm not 100% sure how I would set up a booster for that. Which leaves me wondering if the clock pulse on them should be that high or is there a heater terminal on them that will take a constant 60v/170v and wait for the 5v pulse from my logic circuit.
My circuit is running off of 5 volts, and was thinking of boosting the voltage with something like this:

Adapted to 170vdc if I use nixie, which I most likely will. I hope this all makes sense. A quick recap on the question at hand, How in tarnation can I setup nixie tubes as my display for a logic clock with a 5 volt power supply. Am I on the right track? How might I change the above circuit to step up 170vdc from 5vdc?(just a bigger inductor?)

#### Wendy

Joined Mar 24, 2008
23,396
Welcome to AAC! There are several clock schematics around, one of our other members basically finished a nixie tube model not to long ago using 4017's. I'll allow him to introduce himself if he so chooses.

I've got a clock for an instructional course half finished for the AAC book in the Feedback and Suggestions forum (I put it there because it will end up being in the AAC book).

BG Micro has some clocks on a chip for sale for around \$2.95 or so. You have to provide the display drivers and 60Hz, and it is ready to go. How about a clock with 1' high digits?

http://www.bgmicro.com/mk50250nlegacyclockchip.aspx

Since this is basically a school project you probably need to design it yourself, but it is always nice to be able to see other approaches.

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#### SgtWookie

Joined Jul 17, 2007
22,230
You're asking a bit much. Getting ~25mA @ 170-180v from 5v in requires a heck of a lot of current.

180V @ 25mA is 4.5 Watts.
Let's say an inverter circuit to boost the HV is 80% efficient, which is really quite good; perhaps overly optimistic. That would require ~5.625 Watts of power in, so at 5v that would be an average of 1.125A input current.

I have a schematic for a 180v flyback converter that runs from 12v, but it won't work for 5v; nor will most other easy-to-build circuits.

Magnet18 has built a few Nixie clocks using 4000-series CMOS ICs; his design operates from 12v. You might do a forum search for Nixie clock.

Ronald Dekker's site will be a great resource for you.
http://www.dos4ever.com/
Scroll down to the Nixie clock section. Check out his "Flyback converters for dummies" section first; it is a very well-done page and a great help for a layperson to learn about boost regulators and flyback converters.

His Nixie I is a real beauty!

Please do NOT attempt the mains-powered supply idea in the FAQ; you must use a transformer to ensure that your circuit is isolated from the mains.

#### Wendy

Joined Mar 24, 2008
23,396
Please do NOT attempt the mains-powered supply idea in the FAQ; you must use a transformer to ensure that your circuit is isolated from the mains.
This piece of information is critical if you use this site to help with your project. It is one of the hard core rules here, because it is a major safety issue.

#### Rocky_circuits

Joined Nov 1, 2011
57

It definately appears that 5 volts won't work for this. So I will most likely operate the clock using two different power supplies.

Aaah, with so many potential circuits to make, it's hard not to follow these circuits for my own clock.. But that would be cheating and wouldn't do me much good now would it. Excluding something like the flyback converter where it would be important I carefully do that circuit correctly as to not blow something up like I did in my dorm room the other day...

So for my class we have been commonly using 7xxx series chips. I'm sure we could use 4xxx series too (remember I'm new to the engineering world so I don't have all the lingo down). But that oh so tempting BG micro clock chip looks so wonderful but I think that would be cheating.. Not that the guidelines say anything about what I can or cannot use, just that I need to make a functional clock circuit.

This should porbably be posted under projects if anyone can move it.
I think I'm going to use Burroughs B-5853 tubes since they are relatively easy to come by. Except its data sheet. I can't find the bloody thing! arrrrrgggg

#### Wendy

Joined Mar 24, 2008
23,396
Don't sweat it either way. Relax, and allow this to be a fun project.

I've currently got a half build CMOS clock I'm designing for the AAC book. The clocks seconds and minutes are working, as is the crystal time base.

I mentioned this on your other thread, but it would be silly to design everything from scratch. The crystal oscillator in my clock, for example, came straight out of a data sheet.

More than half the art of design it matching blocks together anyhow.

#### magnet18

Joined Dec 22, 2010
1,227
Hello Hello, welcome to the club!! Where do you go to college?

I would strongly recommend 2 power supplies. 1, 5V is pretty low to pull 170V from, as wookie said. 2, it will make it easier to keep your supply rails well behaved. If you want to keep it simple, you can use one 12V supply leading into the clock, and then use it to both power the tubes and step it down to power your logic. Or you can use 12V chips. It makes life easier in the long run. Up to you though.

My personal favorite for tubes in the IN-14, though many people prefer the IN-16, pretty similar, but smaller and cheaper. As for the datasheets, they can be kinda hard to find, in english anyway. If you google "IN-14 datasheet" the first couple results should be useful. Some tubes are impossible to find information on.

As for other circuitry, As they said I used the 40xx logic chips, primarily the 4017 decade counters for the logic with a crystal for time, though if you wanted I'm sure you could derive the time from the mains frequency. (remember to use galvanic isolation and whatnot, bla bla, etc etc, safety junk)

To drive the tubes I used MPS-a42 transistors, look into them.

last post has a zip, should have all the junk in it.
I would also strongly recommend reading this site from top to bottom- http://www.mcamafia.de/nixie/ncp_en/ncp.htm
It's what I based my design off of and pretty much walks through all the logic.

Also, keep in mind that I'm just a high-schooler, so you could probably improve on my design if you wanted. And don't just copy my schematics, that would be lamesauce. (if you do, you'd better tell me what grade they get!!!)

Have fun with it, and at some point in the near future, you WILL fry something with 170 volts (and you'll probably shock yourself once or twice too), so I'm preemptively telling you not to let it get you down.

Best of luck and stuff!!!

editing, also, look at this- http://www.sphere.bc.ca/test/nixies.html

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#### Rocky_circuits

Joined Nov 1, 2011
57
Ah! Magnet18, I've looked through some of your stuff on the forums already and they are quite informative. Did you happen to make your PCB through multisim? I can't seem to find a plugin for it for nixie tubes. But we are also using version 5.1.... from the 90's.

Let me recap how I had most this planned out so far:
11-26 (maybe an old PC power supply. Plenty of current for 12v) volt power supply that is converted to 180v with something like this if I don't make it myself: http://www.allspectrum.com/store/ni....html?osCsid=c3579c3f3633a6633d59d48f45f01024

Then using the 5v power supply I built with a 7805 regulator, I would power a circuit made of 74161 4 bit binary counters. I know everyone says it would be much easier to use to use a 4xxxx like the 4017 you used, but I'm tellin you, there's nothing wrong with binary! I already have that circuit made in multisim, but I'm not at school so I don't get a picture of it till later

The binary counters would feed into the 74141 decoder. At this point I become a little confused. I've looked at a lot of circuits but still don't see how it works. I understand that the chip connects to 0-9 cathodes, and when you want say 5 turned on, you short that cathode. But how is it being shorted? When I looked at the logic diagram, it looks like it would simply send 5 volts through and not ground anything.. I've looked around but can't find how it works. Unless the GND on the IC is meant for the 180v ground, then it would make lots of sense.
My guess is that maybe you put transistors between the cathode and the pin outs of the chip. So when logic high is presented to the transistor, it turns on and allows the cathode to be shorted to ground. My understanding of transistors isn't very high though so I could be wrong. I looked at the transistor you mentioned, if my knowledge of transistors is correct, then that would work great. Just means I need 60 of them.. D: But then I would still be confused as to why the chip would need to be able to handle 60 volts..

And finally the 180 volt power supply attached to the anode of each tube with a yet to be determined resistance. With one of the pages you linked I calculated 5kohm but that seems lower than what I've seen in other nixie circuits.
Oh and I got to the University of Colorado at Boulder

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#### magnet18

Joined Dec 22, 2010
1,227
Ah! Magnet18, I've looked through some of your stuff on the forums already and they are quite informative. Did you happen to make your PCB through multisim? I can't seem to find a plugin for it for nixie tubes. But we are also using version 5.1.... from the 90's.
I did it once in express PCB, then again in Eagle. Both times I made custom parts.

Let me recap how I had most this planned out so far:
11-26 (maybe an old PC power supply. Plenty of current for 12v) volt power supply that is converted to 180v with something like this if I don't make it myself: http://www.allspectrum.com/store/ni....html?osCsid=c3579c3f3633a6633d59d48f45f01024
I bought one of those. It works, but I would recommend not wasting money, and building your own. I can vouch for this design -https://docs.google.com/viewer?a=v&...4yGQ9t&sig=AHIEtbRe3B8BhBgGLeRBB6j1JOYhXuUZhA
Then using the 5v power supply I built with a 7805 regulator, I would power a circuit made of 74161 4 bit binary counters. I know everyone says it would be much easier to use to use a 4xxxx like the 4017 you used, but I'm tellin you, there's nothing wrong with binary! I already have that circuit made in multisim, but I'm not at school so I don't get a picture of it till later

The binary counters would feed into the 74141 decoder. At this point I become a little confused. I've looked at a lot of circuits but still don't see how it works. I understand that the chip connects to 0-9 cathodes, and when you want say 5 turned on, you short that cathode. But how is it being shorted? When I looked at the logic diagram, it looks like it would simply send 5 volts through and not ground anything.. I've looked around but can't find how it works. Unless the GND on the IC is meant for the 180v ground, then it would make lots of sense.
My guess is that maybe you put transistors between the cathode and the pin outs of the chip. So when logic high is presented to the transistor, it turns on and allows the cathode to be shorted to ground. My understanding of transistors isn't very high though so I could be wrong. I looked at the transistor you mentioned, if my knowledge of transistors is correct, then that would work great. Just means I need 60 of them.. D: But then I would still be confused as to why the chip would need to be able to handle 60 volts..
Your guess is correct, the transistor is used to pull the 180V cathode to ground, allowing the tube to light. It makes more sense to think about the electrons coming from the negative end, and being pulled to the 180V anode.

I don't know where you're getting the 60V number from, and you only need 44 of them.
And finally the 180 volt power supply attached to the anode of each tube with a yet to be determined resistance. With one of the pages you linked I calculated 5kohm but that seems lower than what I've seen in other nixie circuits.
27K is a better number, how did you calculate 5?
Oh and I got to the University of Colorado at Boulder

#### Rocky_circuits

Joined Nov 1, 2011
57
The site you linked to read top to bottom is where I got the 5k resistor from. I just didn't put in the current value correctly is all.

The 60 volts is what the 74141 chip is rated to handle. Just doesn't make sense to me considering it never sees that high of voltage.
44 transistors does make sense doesn't it.. Considering you're not using all 10 pins on each tube.
I'm pretty sure I have it all worked out, I just need to really draw the circuit out. Main problem being is that my clock circuit that I thought was good to go doesn't really work anymore. blahh. I just need to redo it in the 4017 chip instead of these 74161 binary counters.. But at that point it leaves me wondering what the point of the 74141 chips would be/
Do you mind if I throw a few questions at you through a PM?

#### SgtWookie

Joined Jul 17, 2007
22,230
It's best if you carry on conversations in a thread. That way you don't miss input that someone else might have provided, but the big thing is that the conversation has continuity. If it's in PM's, it can get jumbled up in a hurry. Also, it's good to share what has been discussed; keeping it in a thread leaves the decision to review up to the viewer.

#### Rocky_circuits

Joined Nov 1, 2011
57
Alright, I'm cool with that

Are you sure that the 74141 chip's ground is not the 180v ground? Considering it claims to handle 60 volts (after the tube voltage drop) it only makes sense that this chip is meant to connect its 0-9 pins straight to the 0-9 cathodes. The GND on the chip would then be meant for the 180volt ground.
This part is confusing me to no end. Do I need transistors or no? I feel like I shouldn't, but it also somewhat makes sense that I would....
Here is a picture of my clock circuit that I fixed.. and is working now (minus having the ability to set it, not sure how to do that yet)

Now if you can imagine it, I plan on taking the output of each 74161 chips QA-QD and putting them into A-D on the 74141 chip. Then the 0-9 on those chips would connect to a High Voltage Transistor's base (if I do need to use the transistors) and the transistor would correspondingly attach the Input to the cathode of X number and output to the 180v ground.

At which point I would imagine everything works. What do you think?

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#### magnet18

Joined Dec 22, 2010
1,227
well, I've never used a 74141 before, I'll try to look through the datasheet at school today and get back to you.

also, fwiw, i have nothing against pm's, but it is better to ask most questions on the forum, that way more people can look at it and help. No one person knows everything.

#### magnet18

Joined Dec 22, 2010
1,227
OK, I looked at the datasheet, and from what I could gather, when the output is high it is outputting 60V, preventing the cathode form lighting. When low, it drops to 2.5 V, and the tube lights. It is a kind of a confusing datasheet, if someone else wants to look at it to verify I would appreciate it.

#### Rocky_circuits

Joined Nov 1, 2011
57
Yeah that's what it seems like... I suppose. But doesn't it have to tie to the 180v negative terminal somewhere?
Ugh this chip is bloody confusing. I definately want to use it though, I just would like to understand it first. Everything I read about it doesn't really explain it. I emailed someone who posted a project of their nixie clock and hopefully he replies.

#### SgtWookie

Joined Jul 17, 2007
22,230
The 74141 has open collector outputs. It doesn't source anything; it can only sink current.

As I mentioned before, the outputs are only rated for 60v. If you decide to go higher than that, it's up to you - I advise against it.

#### Rocky_circuits

Joined Nov 1, 2011
57
Ok, I think it is starting to make more sense then.. I did not know what an open collector was, but wiki explained it pretty well.

So how this is shown, I would would connect the Open collector, being a pin 0-9 directly to the cathode of the tube. Then the GND on the 74141 chip will be grounded to the 180v ground. This way I do not need any external transistors. Don't worry about the voltage though, the voltage after going through the tube will be 60 volts or less.
So if that is the case, this is great and will be pretty darn simple!

Which makes me wonder how the 5v Vcc input pin works since it isn't being grounded in its 5volt circuit in this chip then.

#### magnet18

Joined Dec 22, 2010
1,227
Ok, I think it is starting to make more sense then.. I did not know what an open collector was, but wiki explained it pretty well.

So how this is shown, I would would connect the Open collector, being a pin 0-9 directly to the cathode of the tube. Then the GND on the 74141 chip will be grounded to the 180v ground. This way I do not need any external transistors. Don't worry about the voltage though, the voltage after going through the tube will be 60 volts or less.
So if that is the case, this is great and will be pretty darn simple!

Which makes me wonder how the 5v Vcc input pin works since it isn't being grounded in its 5volt circuit in this chip then.
I believe you to be correct. Though I wouldn't assume that the voltage will be less than 60V, it might be more, you should check this. I believe it depends on the tube.
You seem to be confused about the grounding, make sure that the tube power supply has the same ground as the IC, otherwise you sill have problems.

#### Rocky_circuits

Joined Nov 1, 2011
57
I believe you to be correct. Though I wouldn't assume that the voltage will be less than 60V, it might be more, you should check this. I believe it depends on the tube.
You seem to be confused about the grounding, make sure that the tube power supply has the same ground as the IC, otherwise you sill have problems.
Well for the IN-8, the data says that it runs at a nominal 180v (nominal means I should run it at that voltage right? For the longest life atleast). It also says it has a voltage drop of 150 volts. leaving only 30 volts that will run through the IC. I still don't know why the 74141 has a Vcc for 5 volts if it doesn't have a ground for it. buut I will just test it out and see how it works. So Magnet18, with the site you linked me featuring that calculator, it says I do not need a resistor if the voltage on my supply matches with the anode voltage I want.. I don't think this is correct. If it is not, how do I find out how big of a resistor I need?

#### magnet18

Joined Dec 22, 2010
1,227
Well for the IN-8, the data says that it runs at a nominal 180v (nominal means I should run it at that voltage right? For the longest life atleast). It also says it has a voltage drop of 150 volts. leaving only 30 volts that will run through the IC. I still don't know why the 74141 has a Vcc for 5 volts if it doesn't have a ground for it. buut I will just test it out and see how it works.
Yes it does, everything has the same ground.
So Magnet18, with the site you linked me featuring that calculator, it says I do not need a resistor if the voltage on my supply matches with the anode voltage I want.. I don't think this is correct. If it is not, how do I find out how big of a resistor I need?
I don't thing you'll need a resistor, try hooking it up without one, and seeing what happens.
It's easy to tell if somethings wrong just by looking at the tube.

You could also increase the supply voltage by 10 or 20 volts, and then drop it.
Inefficient, but simple, and guaranteed to work.