Nixie Tube Ornament




The Nixie Tube Ornament is a homage to the light-up&motion ornaments from the early 90's. The ornament looks cool on a tree and makes a great gift. Finally, a use for IN-12/15 top view tubes!

I used an IN-15A symbol nixie in this ornament. An IN-12 works great too.

A video of the ornament alone:

A video of the ornament in my tree. (Yes, the walls are changing color. I have the si-light system in my apartment: )

Details you will find in this instructable:
1. A small high voltage power supply that runs the tube.
2. A tube carrier to mount the nixie tube in a socket so it can be changed.
3. Firmware that runs the power supply and changes the digit displayed on the tube.

Everything you need to make your own nixie tube ornament is included in the project archive:
1. Circuit board in Eagle (Cadsoft).
2. Compiled firmware HEX file, and Mikrobasic source for the free (demo) Mikro compiler.
3. This instructable in .odt (Open Office) format.

Step 1: Design Overview

The nixie tube ornament has 3 main parts:
1. A power supply – boosts 5 volts to 180 volts for the nixie tube.
2. A tube driver – changes the lighted tube digit by grounding one of the 10 tube cathodes. I used the Russian KD155-whatever.
3. A microcontroller – a PIC microcontroller ties everything together – it runs the power supply and changes the digits shown in the nixie tube through a four wire interface to the tube driver IC (see previous).

Step 2: Power Supply (Boost Converter)

Nixie tubes are powered by a high voltage source (about 180 volts). To get this voltage we use a boost converter. An induction coil is abused pump-like to fashion 180 volts from 5 volts. Cool. Everything I know about boost converters can be found in this instructable [].

The actual power supply design is taken from my attempt at a nixie watch, see it here []. The main difference between this supply and the reference supply in the boost converter instructable is a reduction of components. There are no indicator lights, no large expensive filter caps, and only one input cap. Since the ornament is a single tube, dropping a few capacitors has no functional impact.

I also dropped supply voltage calibration. In the reference design the PIC measures the input voltage and calculates the ideal charge and discharge time for the inductor given the inductor size (mA) and value (uH). I just calculated the charge/fall time for the coil based on a 6 volt supply and hard-coded these values (worst case scenario with 4 AA batteries, though I use NiMH). If the supply is lower (as with my NiMH) the coil is not being used to its full potential, but it doesn't matter because we only need a few mA of HV for a single tube. Sweet. And we saved 2 more resistors. More than 6V will probably cause over heating in the inductor/FET.

Note: There is a 5.1v zener with 1 ohm resistor to protect the uC if the supply is > 5 volts, but this isn't a problem with NiMH or a wall-wort

Step 3: Tube Carrier

The 'tube carrier' is the face of the ornament It holds an IN-12 style nixie tube socket and the KD155 nixie tube driver IC. I cut the circuit board to fit around the nixie tube socket and screwed the socket to the board. Long screws were used so that the power supply could be bolted to the back.

Assembly was a bit intense. Wires from the IC to the nixie tube socket were soldered directly into the same hole as the IC. Not a great design, but it worked and saved a lot of space. The leads connecting to the tube socket were covered with shrink tube for a more professional look (but mostly to protect against shorts).

Step 4: Firmware

The firmware is really simple:
1. First, values for the power supply are loaded into the pulse width modulator registers.
2. All the ports, timers, and what-not get setup.
4. Timer 1 is setup with maximum pre&post scalers, on interrupt the nixie digit is changed.
3. The firmware then enters an endless loop of measuring the output voltage and applying pulses to the FET.


Step 5: Ball Insertion

I saw a cool 'make your own memories' clear plastic christmas ball at the store. It twisted apart so you can put something in the middle. This project originally intended to use one of these balls, but once finished the balls were sold out. This is the next best thing available.

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    33 Discussions


    5 years ago on Introduction

    Once nixie tubes were cutting edge technology, only used in top-of-the-line test equipment, now they are forced into the shame of what hobbyists do to them. HA! They are really cool, and that circuit is really neat. I ordered some IN-12,IN15, and Z574 and plan to play with them soon! Basically do something like this!


    8 years ago on Introduction

    OOooo great. I'm from russia, and i realy surprise to see IN here=)


    9 years ago on Introduction

    Thats really cool! I like the idea of a retro tree ornament, its a shame you didnt have a job lot of these and make a set of ornaments. I think they would look great all flashing away like they do with random characters. - Tvmender


    10 years ago on Introduction

    Your nixie tube shows random characters insteard of numbers! I want this sort of nixies, too.


    12 years ago

    It seems like an extraordinarily bad idea to go stringing high voltage on your Christmas tree, plus a poor use for what must be an almost extinct type of vacuum tube. Or am I missing something obvious?

    4 replies

    Reply 10 years ago on Introduction

    this does seem like a bad idea if something were to short across the hv power supply it could set the tree on fire.


    Reply 12 years ago

    Technically, you really can’t say that high electrical voltage is dangerous because its not, electrical current is. That’s a common misconception. I don’t know what amount of current to expect from this project but from an electrical engineering standpoint, you can’t judge how dangerous something is based on voltage alone. The static electricity to hold a balloon to the wall after rubbing it on carpet a few times can create 10,000 volts easy but virtually no current. Another example is the old Van de Graaff Generators (the metal balls that make your hair stand on end). Remember the signs that say “Danger – High Voltage!” still mean “Danger”… but the “High Voltage” part was not suggested by an electrical engineer. So consult an electrical engineer before making your next sign for proper terminology ..haha, just kidding. Great instructable ian! This is some really nice work.


    Reply 12 years ago on Introduction

    I have a 5" BW battery powered TV, that most likely 5K volts inside the cabinet, safe to use unless the cabinet is opened or breached somehow. The same is true for tree ornament. I'm not so sure it's a poor use of what may be a rare device. What would a waste is for it to sit on a shelf for years and eventually tossed, because lack of demand. Ian did nice work, archiving is just as nicely. However the end product may not everybody's "cup of tee", I jut really don't see a hole lot of persons duplicating this project, thereby any depleting existing stock. I would think most persons looking to duplicate the ornament would chose an LED display


    Reply 12 years ago

    I wouldn't really consider the HV 'strung' through the tree. Its pretty contained. Also note that the 'HV' in the nixie ornament is a few mA of 170V DC, while the christmas lights are strung about the tree and are actually higher voltage at 220V AC.

    I planned to put the whole thing inside a clear plastic 'make your own memories' christmas tree ball, a sphere with two halves that snap together. Unfortunately, the store was sold out of them by the time I finished the project.

    IN-12's are really common and cheap, but yes, the IN-15 is somewhat rare. I had to track mine down for previous project I've yet to complete.

    TJ 2

    11 years ago on Introduction

    Really cool project! too bad there arnt many of those types of vacuum tubes left though or I would have made one.


    11 years ago on Introduction

    That's pretty awesome! (love the knife too, aren't they great?) Love the nixie tubes, I have GOT to pick some of those up. so much better looking then leds.


    11 years ago on Introduction

    Nice tutorial, the SI light system would be cooler if it like changed the whole color of your wall though/ your walls were like huge monitors or somethin', ('sept that'd probly cost too much...) Anyways I give this a 10/10. :)


    11 years ago on Introduction

    COool! Perhaps, you could use the tubes for turning the tree to a hifi amplifier too. ;P


    Reply 12 years ago

    Its an instructables laser etched leatherman. I won an orange one and a purple one in the first two instructables project contests.