Introduction: IN-12 Nixie Clock

Picture of IN-12 Nixie Clock

Ever since i discovered nixies i wanted to make a clock with them, but all the designs i found were for 4 or more nixies, required a custom power supply and a complicated driving system.

As the cheap guy i am, i didn't want to buy lots of nixies or components to make such complicated circuits. And after ages looking for a simple clock design i came up with this page.

This clock uses a single chip which i've already used before, the PIC16F84A. The circuit is also pretty simple since it uses a single nixie, driven by discrete transistors and doesn't need a powerful HV supply.

In the page only the schematic and code are provided because this guy builds his circuits on veroboard, But i wanted to make a good-looking clock so i decided to design and make a PCB.

The tube i've used is an IN-12A, but a B variant can be used as well (or any other nixie tube with the proper circuit modifications). The high voltage supply uses components from a disposable camera, so it also costs almost nothing.

The clock displays the time periodically flashing the digits from tens of hours to minutes.

To set the time you have to push the button when the digit you want to change is being displayed, it will increase each time you push and cycle from 0-9.

If you hold down the button during power on, the clock will rapidly cycle trough the digits. It is useful to kill off some "cathode poisoning" on nixies that have not been used in a while.

Step 1: The Main Board

Picture of The Main Board

The main board contains all the components except the high voltage power supply, so anyone can build a different HV circuit without changing this board.

The .brd and .sch files are available so you can modify the circuit as you please

The PDF file is linked down so you can make your own PCB.

The components needed for this board are:

-The IN-12 tube (4$ on ebay)

-A PIC16F84A

-10x high voltage SMD transistors (I've used the MMBTA42)

-13x 0805 resistors

-A 4MHz crystal

-2x 22pF capacitors

-A push button

-2x 2pin female headers + 1x 2pin 90º male header

-Fine soldering skills

Step 2: High Voltage Supply

Picture of High Voltage Supply

This high voltage supply uses components salvaged from a disposable camera (only the transformer, the diode and the output capacitor). T reverse-engineered the camera circuit and made this one with the same design.

I've changed the original trough-hole transistor for a SI2302 mosfet and reversed the diode for a positive voltage output.

The LM317 lowers the 5v imput to the 1.5v the circuit needs. The copper fins keep it cool during operation.

To use this same circuit, you should check if the transformer you use is connected in the same way to the rest of the components (has the same pinout).

If you use a different mosfet, make sure it has a low on-resistance so it doesn't dissipate much heat.

Step 3: Program the PIC

Picture of Program the PIC

To program the code into the PIC, you'll need a programmer circuit and software for it. I used a chinese k150 programmer with the software it came with. You need to load the .hex file into the program, and burn the chip with it.

Some of the program features are:

It keeps time very accurately.

Works in 24h format.

If you set a wrong time (like 26:72) it will eventually autoreset.

There is a chime logic pulse output on pin 2 (RA3). The logic output will give a number of pulses in accord to the hour when the minutes turn to zeros. For instance, there are 8 logic pulses from pin 2 when the time turns to 8:00. The output is not an audio frequency, it is a simple logic pulse, so one would need an tone or chime generator for the audio.

Holding down the time set switch while the clock is first powered up will set it in a test mode that cycles through all the digits. It is useful to kill off some "cathode poisoning" on nixies that have not been used in a while.

If you programmed it correctly, the first time you power it up it should start at 10:00 (unless you hold down the button)

Step 4: Ready to Work

Picture of Ready to Work

The finished clock could fit in a 35mm (1.38 inch) sided cube. It can be powered with a li-ion battery or an usb cable (3-5.5v) and consumes about 150mA

I would have made a case for it but i didn't find any suitable material, i hope i could 3D print an enclosure.

If you decide to build this clock, remember that it uses high voltage (up to 400v). The HV supply i used isn't capable of killing anyone, but that doesn't mean it can't shock the hell out of you.

If you have any doubt about the instructable or need any help, fell free to ask it in the comments.

Also, you can vote me for the Make it glow contest.


CyberpigsotJ (author)2017-10-12

Will the circuits and high voltage supply work with an IN-17 nixie?

Mesopexia (author)2017-08-05

Hey! I made the circuit on a breadboard with a 555 based power supply. When testing, the PIC runs about 10 times faster than it should. I checked every connection, every part (including the crystal). Any ideas what might be the cause of such issues?

CK101 (author)2014-12-16

Did you use a IN-12 a or b ? Is there a difference

Kyerohtaron (author)CK1012015-11-16

The only difference is that the IN-12B has a decimal point in the lower right corner. That's all!

SławekD1 (author)Kyerohtaron2016-11-24

Can I use in-4 instead of in-12?

FLotSam made it! (author)2016-04-13

Many thanks for the instructions!

This is my short video:

DuaneJ1 made it! (author)2015-07-06

Thanks pinomelean for all your advice and posting this project. I've opted to used this for the power supply, so voltage is all standard 3.7V. The total current is about 50mA so I am going to have two separate batteries 1 for the clock side and 1 for the HV side. Thanks!

A suggestion for the battery idea, but you might as well use a RTC module to keep the time between power cycles.

p8662 (author)2015-12-10

I have no experience in these stuff, planning to build one. I have question that confused me a bit.

I've noticed copper fin is gone in the final product. Was it useless?

I see on step 2 picture +5v, GND ,GND, HV+ have male pin. is it pulled from male header?

What are those files brd,sch,hex,asm files are used for?

I Hope I don't get answer after a year ha ha

p8662 (author)p86622015-12-10

Additional question, on step 1 is the red line on purple pcb board wire?

p8662 (author)p86622015-12-10

More questions, what part do I need to connect batttery and this invention, how to recharge the battery

If you look online, you can find Li-ion chargers that you can connect the battery to. The one I had (before I fried it accidentally) could be plugged into with a mini usb cable.

pinomelean (author)p86622015-12-11

The red lines are jumper wires if you're making a single layer PCB.

p8662 (author)pinomelean2015-12-11

thanks I'll look forward your answers

dudalsdjaak (author)2016-02-12

what kind of 0805 resistor you used on main board?

pinomelean (author)dudalsdjaak2016-02-13

The cheapest i could find o ebay.

dudalsdjaak (author)pinomelean2016-02-13

lol thank you

DuaneJ1 (author)2015-06-06

Really cool project, I've never programmed a PIC before how did you work out the program. Do I need to use the .hex and .asm files to write to the PIC? What can I use to do that? Sorry I as I've said I'm a newbie. Thanks.

pinomelean (author)DuaneJ12015-06-07

The .hex file is the one you have to program to the PIC

FLotSam (author)2015-05-26

It's such a cool thing. I really want to repeat it. But I have a problem with the power board, I do not know what a transformer, a diode and a capacitor you have used and from which it took the camera. Tell please for more details about these and write their characteristics. I need your help, please help me.

pinomelean (author)FLotSam2015-05-26

I've got no clue of what transformaer that is nor i know the diode. All i've done is take a dosposable camera, reverse-engineer the circuit and replicated it. I used smd resistors but i could have used the original ones.

Not all camera circuits are the same, most transformers have different pinouts even though they share the same windings.

That's why i made the HV supply on a different board, so everyone can make a different one, with different components. Just get your camera and replicate it's circuit.

leomiranda (author)2015-01-29

Nice project! This is what I was looking for!!! I have all electronic pieces, except the crystal with the value you used. I have with 16000 Hz (M16000). Programming is not my favorite cup of tea. Could you help me showing what I have to change in the code to use the crystal I have? Thanks

pinomelean (author)leomiranda2015-01-29

I'm begining to program PICs and i don't have much experience or knowledge, but i know enough to tell you that changing the oscillation frequency is going to be a mess.

Since the whole program is about timekeeping, you would have to change a lot of things and it would require lots of work.

I really recomend you buying a 4MHz crystal, they're not expensive and will save you the headache.

snoop911 (author)2015-01-02

Just curious why did you choose the 16F84A? I've noticed that same PIC on similar projects... is there something particularly well suited for this application as opposed to other PICs in the low-cost line (16F1936, etc)?

pinomelean (author)snoop9112015-01-03

I used the 16F84A because the original project used it and i only modified the code a little.
I usually work with the 16F628A which is the upgraded modern version of the 16F84A.
They both have 18 pins which was the right amount for this project and are pretty common and available.

The 16F628A has a good amount of memory, two 8bit ports and lots of other features that i don't even know about.

CK101 (author)2014-12-14

How do you make pcb I'm a rookie with this stuff and have no Idea what do so with the pcb or the other board
Help please

pinomelean (author)CK1012014-12-15

There are a lot of ways to make a homemade PCB and there are a lot of instructables that explain how to do it.

If you don't feel like making your own, you can always order them to pages like oshpark, dirtypcbs and a lot more

Bob1560 (author)2014-12-14

Clever idea and nice design. I am not able to download any of the files, please tell me how this is done. Thanks!

pinomelean (author)Bob15602014-12-14

If you can't download them with a left click, try right-click, "save link as" and select the folder you want to save it into.

Bob1560 (author)pinomelean2014-12-15

Got it, thanks! A right click, then "Save link as" yielded a file to save.

Bob1560 (author)pinomelean2014-12-15

Got it, thanks! A right click, then "Save link as" yielded a file to save.

CK101 (author)2014-12-14

I also need help with the hv part I don't understand what I must do there . I got the link for the the pcb though .

emil.godjaev (author)2014-12-06

Interesting design. I got few questions: will it work with IN-4 or 14 after a changing a contact pad, and could you write a characteristics of transformer?

pinomelean (author)emil.godjaev2014-12-06

With both IN-4 and IN-10 it should work the same, they have similar operating current and voltages.

About the transformer, i have no idea how it works or what it characteristics are. I just got it from a disposable camera and copied the circuit it was in so it would work.

nodcah (author)2014-12-01

That circuit board is soooo well designed!!

It would probably save a lot of battery if you only saw the time when the button was pressed (interrupt based sleep?) But great project! =)

Ruedi_68 (author)2014-11-26

Looks great, how long does the clock runs whith the Batterie you use?

pinomelean (author)Ruedi_682014-11-26

I tested the clock run time with two batteries, a 650mAh and a 4000mAh one.

The first one was just the size of the clock PCB, but it provided 4h run time.

The other one dured almost a whole day but it's enormous.

(photos with the 650mAh battery)

FyreHawk18 (author)2014-11-25

Is it possible to change the display to LED?

pinomelean (author)FyreHawk182014-11-26

I have another instructable about a numitron clock in which you can use a 7-segment LED display instead of a IV-9 numitron.

mk2001 (author)FyreHawk182014-11-25

Yes but I think the entire point of the project is he's using a Nixie display

dzenizo (author)2014-11-25

Nice approach, and nicely done!

Many years ago in the 70's I built a similar concept hardware-only clock for my father, following instructions from an electronics magazine. It was based in a 2314 clock chip with some discrete circuits to decode each digit in sequence.

I later built some other designs using fluorescent and LEDs displays because nixies were scarse.

Congratulations on your design

pinomelean (author)dzenizo2014-11-25

Thanks, sir!

jphipps (author)2014-11-25

Would it be possible to code this to where the circuit is modular and expandable. Such as the bell pulse also having a PWM digital synchronizing signal within the pulses. Then connect that pin2 to the pin2 (or another blank pin if there is sorry I'm on my phone and couldn't see the pcb) or maybe replace the push button's pins on the second third ect tubes as a daisy chain in/out or just signal in. This way if one wanted to use your simple design we could make a 2/4/6 digited display. Heck depending on yours or someone elses programming skills these could be sold and marketed as modular universal displays for anything.

pinomelean (author)jphipps2014-11-25

It probably could be done, and drive more nixies just by adding a transistor for each nixie and switching between them fast enough to not apreciate it. But you would need another PIC because this one lacks the pins to do so.

(you would need an extra pin for each nixie you add)

Anyway, that is a grat idea and totally worth exploring.

dougstrickland (author)2014-11-25

This is a nice physical design. Very modular and adaptable to various power sources, plus incredibly compact. Well done!

mscheyhing (author)2014-11-25

This is awesome and inspiring! I'd like to do stuff like this when I'm retired. (Unfortunately I don't have the time now between day job and honey-do's).

MarcusAvery (author)2014-11-25

LOVE nixie tubes!

iam_maker_leo (author)2014-11-23

Wow... Cool....

I love it.... and want to have it.

it is very looks good nixie clock...

dpizetta (author)2014-11-23

Woou, this is amazing!

About This Instructable




Bio: I love electronics and all about DIY.
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