Simple user-adjustable DIY Nixie Clock

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As first instructable of the year I managed to finally complete my age-long nixie clock project.
Nixies are neon valve tubes, where ten cathodes have shape of digits and are lighted up by plasma when high voltage flows through them. I love these old era displays, which have been employed in last century before I was born.
In last year I've been slowly collecting components and knowledge to build some nixie clocks as Max Pierson's beautiful creation, I like the old style, the roundness of glass tubes, the rough wood case, the simplicity of the design. That clock has definitely inspired my project. Even though I really love vertical digits arrangement I keep that original feature for my next clock.

Therefore this first born is a six digits horizontal wood desk clock, with six big round Russian IN-4 nixie tubes, no dots, no visible buttons, no LED illumination, only a big massive rosewood block and the power of plasma ;-)
I have to explain you what the title means:

simple because it can be entirely built with common tools and from common components, you only have to order six IN-4 nixies and one nixie driver

user-adjustable because it's predisposed for many external sensors and additional features (as neon dots between digits, alarm, etc.)

DIY since you neither have to buy external shields or to pay for pcb manufacturing, just follow my instructable ;-)

WARNING: this circuit raises the voltage to deadly 300V so you must avoid to touch contacts while working, I'm not kidding, please BE CAREFUL!

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akirk1123 days ago

Andrea, GREAT writeup! I'm planning on building this on a breadboard rather than a pcb. I just wanted to clarify a few things before I start ordering parts. I'm going to run it on 9V input only, so I can do away with C9, C10, D3, the 12-35V/9V selector switch, and the L7809? I'm not seeing on the schematic where to pipe in the 9V battery for a backup. Pin 1 on the ATMEGA, listed as PC6_(RESET, has a reset lead coming off of it in the second schematic, but doesn't go anywhere on the first. On the first schematic, pin 12 coming off of the 74141N driver shows it goes to "CND" before ground. I'm still a noob to this, so what the heck is "CND"? Do you also have the updated schematic to use the third position of the on/off/on switch to use as a sleep mode? Thanks in advance!

Hello. i may not be the author, but i can answer your questions ^^

The L7809 block only serves to regulate excess voltage from a big supply to a suitable 9v. if you are using a 9V supply you can safely omit it except for C10 which serves to clean the power a bit...which you probably want.

Regarding the 9v Battery. it can be attached to just the 9V line. Although a slight warning is that the 9v will be depleted in record speed as the project does not seem to be capable of intelligently turn of the Nixie without a external power-source and 9v batteries are not designed to give the kind of power the nixie needs...atleast not for long.

I think you are misreading CND for GND (ground). the reason its double is cause one is a Symbol (which connects to all others symbols on a schematic) and the other is a pin.The reset goes to one of the 2 switches in the upper-right of the schematic with the driver and power-supply. Remember if you click on a image on instructable you will get a better view...if its bigger then the browser can show you can click on it again to download a full-resolution picture! ^^

I thought C10 might serve a cleaning function. As far as the "CND" I was looking at the high res. Still wasn't quite high enough to make it out. I figured it was a ground, but I'm still pretty green at making electrical components. Thank you for the clarification.

andrea biffi (author)  akirk119 days ago

Hi! Actually I don't suggest you to make the circuit on a breadboard, remember you have to do with high voltage, so it's very dangerous, you don't want a wire to disconnect and touch your nose when you are looking the beautiful nixie glow closely!

The battery will work good, but you have to implement a code with an automatic sleep function. Anyway, if you look my second nixie clock ( you will find the updated schematic with 3rd position as sleeping mode, and also you will find a new pcb ready for battery connections. When you connect battery the power-socket disconnects the wall-plug line.

Good luck!

I'm not terribly worried about the electricity. I've been zapped with mains power, 100,000v high power ignition coils, and others I care not to mention. I like the way breadboards look when I put them together. I found your other schematic after I had submitted my first comment. I'll be using that one to build mine. Looking forward to seeing more code implementation that you alluded to in another comment.

Nighter3D10 days ago

Ah i love nixie clocks. Working on a couple of tube clocks myself. Kinda doing a "1 of each". Got a working Nixie prototype (Direct driven through multiple drives and a few shift-registers), Made a design for a tiny Numitron clock (They are the most beginner friendly. writing a instructable on them) and am already expecting some VFD tubes (again to be given a instructable as i work on it. Seem to be very few off)

May i make a suggestion though?

Look up the MC34063. Its a very popular "jellybean" Switching power-regulator often used to design high-efficiency step-up/down power-supplies (also very popular for Nixie supplies!). the only issue i have with your design is namely the Linear regulator used to convert power to 9v. if planning to convert a large voltage like 35v to such a low power that is going to power tubes its kinda innefficient...scratch that HORRIBLY INEFFICIENT (25-30%). Its a shame to have made a highly efficient Nixie switching supply, but to have it fed by a linear supply that is horrible inefficient... also makes for ways to make your own efficient energy-boosters/converters. Heck you can even invert power for Vacuum tubes or make a VFD power-supply.

Personally i avoid the IN-4. The IN-4 and IN-1 are quite known for lacking the Mercury within its gas mixture that most other tubes have. this shortens the life a bit compared to some other Nixies i have around. IN-1 is know to live for months at most and the IN-4 is know to last a year or so. You can see if mercury is present due to a blue hue within the Nixie glow.

andrea biffi (author)  Nighter3D9 days ago

yes, particularly the IN-1 has a very short life, but if you implement a good code to make the clock turn on only when you need it, it will last for 100 years, I'm working on it.

Yeah many tubes can live long beyond their rating if done properly. Especially russian tubes of which the lifespan ratings are quite conservative(e.g. Worst case). a tube rated for 5000h can last for years and those with mercury like the IN-12 can last decades in a well-programmed clock. I pity those planning to use the clunky IN-1 tubes.

andrea biffi (author)  Nighter3D9 days ago

Right, but with my design you are not obliged to use a 35V psu, you can use a 12V one, or even use a 9V power source and bypass the 9V regulator. Good luck with your projects, we look forward to see them as instructables!

janisalnis1 month ago

You could add to improvement list: "Use optocouplers to switch anodes instead of many transistors." Saw this workin on one Ebay board.

andrea biffi (author)  janisalnis1 month ago
Yes I know that possibility, but it's not a real improvement, it's just another way to proceed, but it's much more expensive.
If you are interested you can find the schematic with the TLP627 optocoupler here.
mm0bef2 months ago

awesome looking clock. Been going to build a nixie clock for some time but couldn't decide on style. This is it. Just need to get someone to etch the boards for me and im good to go.



andrea biffi (author)  mm0bef2 months ago

great! I have some spare pcb (new version, see my other nixie clock) so contact me if you need one. I don't have other tube shields but those are much more simple to etch (or you can simply wire the tubes)

SpectrHz5 months ago

What a gorgeous looking clock! I absolutely need to make a project like this eventually :) I really like the wood you used, the nice warm orange glow against that dark wood looks amazing.


andrea biffi (author)  SpectrHz2 months ago

thanks! :)

salexandridis5 months ago


Yesterday I finished the project and I tested it. All nixies lit up apart from the first hour nixie. After some measurements, I found out that one MPSA42 transistor was burned out, so I will replace it soon.

Now, the problem is that when I powered the circuit again this morning I noticed that all nixies would display the digit 2 and the digit they are supposed to display (have a look at the attached photo). Keep in mind that I have already tried disconnecting the K155ID1 pin that controls digit 2 (which is pin 8). Digit 2 turned off on all tubes, but when it was time to display this digit, the nixie would go crazy and a fade "red-ish shadow" would appear around each digit. Do you have any idea about what might be wrong?

Thank you in advance,


andrea biffi (author)  salexandridis5 months ago

Ouch... that's very strange. I would say that there is an high voltage across all anodes when no signal goes to transistors. I found out that there is actually an interference between hv circuit and transistor, but the effects were not so evident in my clock. I designed a new pcb where voltage is constant on all anodes, I'll post it soon here.

ps: you forgot to attach the photo

Thank you very much! What's more peculiar is that yesterday it was working just fine (except for the nixie on the left), but today I got this problem... Anyway... I' m looking forward to new PCB.

Oops! It seems that I did forgot to upload the photo! Here it goes!

andrea biffi (author)  salexandridis5 months ago

new pcb design updated (attachments to step2)!

And here are some more photos!

andrea biffi (author)  salexandridis5 months ago

salexandridis, that toroidal choke in the picture is not good for this high voltage circuit, when I tested it the mosfet, the coil and other parts got very hot! Use a radial inductor as this.

andrea biffi (author)  andrea biffi5 months ago

I updated the guide with this info (step3)

imperio5 months ago

just say, it's nice .... not enough ... this item is rejuvenating!

Imperio from Florence

andrea biffi (author)  imperio5 months ago

Grazie Imperio!

TheFruktus6 months ago

Can i use IN-14 For this project?

andrea biffi (author)  TheFruktus6 months ago

Yes of course, I'm also improving the circuit to remove a magnetic interference between traces, and I'll design an IN-14 clock too.

To use IN-14 you have to change tubes' pins arrangement on the tubes shield.

yeah i figured this out, i was just curious if the voltage will work. Thanks :)

andrea biffi (author)  TheFruktus6 months ago

Yes, this circuit could supply a wide range of voltage, just set the pot to have the voltage needed.

artRiot6 months ago
Awesome, great job man. I love nixes, so cool. I found a good place to buy them back when I was doing a project in school. Check it out
andrea biffi (author)  artRiot6 months ago

cool, tube are also cheap there, but no IN-4 ;-)

no...but a very good friend of him...we talked about you today.... if you have Facebook you can look on my site Titus Timeless

andrea biffi (author)  Titus Timeless6 months ago

Titus your projects are awesome! Please post at least an instructable here :-)

zacnotes6 months ago
Andrea- Great build, the finished product looks fantastic. I have a nixie tube racquetball scorecard that turned out nicely, but it was my first project with any sort of meat to it at all, and i learned a lot that i intend on implementing in my next project, a nixie clock. I will be using the IN-4 tubes as well, but i am finding designing a pcb around them in Fritzing to be difficult. Would you mind making your Diptrace IN-4 part available?
andrea biffi (author)  zacnotes6 months ago

Hi zac, thanks. I'll pm you about the IN-4 part.

Awesome, thanks
valveman6 months ago

Andrea this is so retro I love it! I'm kicking myself for giving away older nixie tube HP equipment.

andrea biffi (author)  valveman6 months ago



Great Job...greetings from Aeon Junophor

andrea biffi (author)  Titus Timeless6 months ago

Are you incognito, Aeon? ;-)

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