Picture of Single digit numitron clock

Numitrons are neat display devices similar to nixie tubes but designed for much lower voltages. Numitrons are basically incandescent displays in which filaments create the segments.

They have a retro look that i liked so much. I bought 6x IV-9 russian numitrons in ebay, they were about 3$ each, they're pretty cheap!
At that time i didn't know what to do with them, but then i thought about a clock. Using software from a single LED display clock i made this impressive numitron clock.

Step 1: Program the PIC

Picture of Program the PIC

The original purpose of the software was to drive a single common-anode LED display rather than a numitron, but either way works.
The software was modified to flash the digits so the HHMM LEDs wouldn't be necessary. Also the software was modified so if the tens of hours is 0 then it is not displayed.
Moreover, the software does not check the input values so entering the wrong time such as 67:85 would be accepted, but eventually the clock will start resetting the digits correctly.

The clock operates off a PIC 16F84A using a program written by David Tait (software is further down this page). The crystal oscillator for the clock is a 4MHz crystal.

I think another microcontroller such as PIC16F628A could also work fine.

edb19841 year ago

Hey there, nice guide -did you got the idea from Jon Stanley's website Electronixandmore? - on there if you read a few of his posts the accuracy of the crystal is addressed with two 24pf capacitors to ground.

if you want to make a watch why not try my design? its made from the same schematic you are using but forgeting the idea of a PCB. runs from one 18350 with a boost circuit to bring it up to 5v. it has the option to turn the LED's on and or off. with LED' on the battery will last about 20 hours, with them off it lasts about a day and a half. please note its not finished yet, and if your wondering the case is 3D printed.

pinomelean (author)  edb19841 year ago

Yes, the software and schematic came from there, i also forgot to use capacitors, but in the secod version (a pocket watch) i've added them an it keeps time a lot better.

You can comment using the "i made it" button, Nice watch though.

My new one is smaller, only 2x3.5x4.5cm with battery and case :)

Cool, did you get anywhere with trying to program it to show the time at the press of a button?

pinomelean (author)  edb19841 year ago

I need to learn a bit more about programming, i'm new in this.

i slightly modded the board so now it is a proper watch :) i added a different button and capacitors to the crystal as mentioned in a comment below

here is a link to a 3d model of the board

pinomelean (author)  The nerdling1 year ago

I'm planning to make a second version, a pocket watch with a battery and so, i'm editing the software so it only shows the time when you push a button, to save energy. It will also use tiny incandescent bulbs instead of LEDs.

Maybe i'll post an instructable about it, but i need time.

Meanwhile you can take a look to the files below, they could be usefull for you!

Mechromancer made it!12 days ago

Great Instructable!

Finally got around to it and decided to make a steampunk watch out of it.

I went with OSHPARK to make me the board. $10.50 for 3 boards, professionally made and with a solder mask. Made the job soooooooo easy. I also opted for SMD LEDs.

I'm using a 3.6v AA Li-Ion rechargeable battery and a micro 5v voltage booster to get the filaments a little brighter.

Looking forward the next version that mention in this thread. Hopefully, it will have a memory back up so you can turn the clock/watch on/off and not lose the time. Or can you add that to this clock somehow??


DuaneJ11 month ago

Hi, I was wondering, with the new numitron w2.brd & .sch will the old hex work with the new design? If not could I get a copy of the new .hex program. Thanks & your projects are really cool.

pinomelean (author)  DuaneJ11 month ago

Sorry, but i ended up not using that board design.

I've made a new one with it's own software, which i'm still testing, but i'll probably post soon.

ma35tr0 made it!5 months ago

I made it and it perfect works! Thank you! But I have one wish - can you add 1Hz blinking led out PIN12 (RB6) ?
I'm used one 7seg led with AC. Dimensions 40x62mm. Powered by one li-ion 3.7v/2200mAh battery. Here is my PCB photos:

mikoto093110 months ago

Thanks for detailed instruction. And I wonder if I can get .hex file that allows to display time when only a switch pressed, not periodcally.

pinomelean (author)  mikoto093110 months ago
I'm currently working ond that and many other upgrades to make a numitron watch.
I will probably publish an instructable when i finish it.
Ploopy1 year ago


florinc made it!1 year ago

I made a similar one, using Arduino Pro Mini:


ihart1 year ago

Awesome project!

pewtu1 year ago
In reply to g4ipz in UK you can get a free non restricted schematic and pcb drafting software Designspark given away by RS components. Are the files available for the redesign which includes the 2 extra capacitors and new layout?
pinomelean (author)  pewtu1 year ago

The .SCH and .BRD files are available in ''The circuit'' and ''PCB design'' steps, you can edit them and modify all you want, but that, without comercial purposes :)

g4ipz1 year ago

Hi Pinomelean. A nice little instructable.

Out of interest which schematic diagram and PCB drafting software do you use for your designs please as I like the end results better than what I use at the moment.

pinomelean (author)  g4ipz1 year ago

I use cadsoft eagle, with this softare you can open and edite the schematic and board files.

Thanks for that but I just checked the price and even the hobbyist version is well out of my price range. Thanks anyway.

pinomelean (author)  g4ipz1 year ago

If you mean the hobbist version of eagle, it's free!

That's why i use it.


This page shows $169 bucks, $69 for the "light" version...

pinomelean (author)  Culito1 year ago

Enter in the ''download'' tab and click on download eagle, choose your os and when you've intalled, choose the free version, it has limitations, but for hobbists is enough.

Id say it more retro than steampunk but its a very cool project. Id like to to see make a case and turn it into a watch

pinomelean (author)  shizumadrive1 year ago

Yeah, a case would make it look better, as i said to the nerdling (comments) i'm designing a pocket clock, just like this but with mini incandescent bulbs, portable with battery and much more features.

zaphodd421 year ago

Had to vote! Had to print it and put it in my "to-do" folder! Great 'ible! Thanx for the work!

When you say single digit, does that mean it gives the time serially? Flashing min, then tens of min, then hours, then tens of hours?

pinomelean (author)  luckylulujoe131 year ago

I flashes tens of hour, then hours, then tens of min, then min. Just like reading the time from left to right.

The LEDs indicate the digit being displayed.

uhclem1 year ago

I am surprised the micro is able to sink/source enough current to light the filaments.

pinomelean (author)  uhclem1 year ago

The PIC16F84A can source or sink 25mA per I/O pin.

But each port has a limit:

Maximum current sunk by PORTA-80 mA

Maximum current sourced by PORTA-50 mA

Maximum current sunk by PORTB-150 mA

Maximum current sourced by PORTB-100 mA

With this clock it isn't a problem since each segment draws 20mA.

I LOVE this watch!

pewtu1 year ago
Gaining 3 minutes a day seems quite a bit. How about putting a couple of 22pf capacitors, one from pin 15 to ground and the other from pin 16 to ground to load the crystal an see if it helps. Like the neat layout.

Says one minute every three days, not three every day; though the latter is still more accurate than the average non-professionally-adjusted mechanical clock mechanism.

pinomelean (author)  pewtu1 year ago

Thanks, i will try it in future projects.

I like it!!


pinomelean (author)  kyle brinkerhoff1 year ago

Thanks, when i discovered them (and nixies) i couldn't think in LEDs anymore, retro displays rule!