How to control a Nixie Tube with Arduino

In this tutorial, you will learn how to control a nixie tube with an Arduino.

Nixie tubes were the only way to display numbers back in the 50s, before VFD and seven segments displays. Today they are highly sought after for their retro / steampunk look.

Using nixies with Arduino is fairly straightforward, but you’ll need a few exotic parts. Read on!

Parts needed

• A nixie tube. In this tutorial a Soviet era IN-14 (ИН-14) is used but it can be substituted for any other tube.
• A Nixie driver IC (KM155ID1, SN74141, 7441, etc. etc)
• 12V power supply
• 12V to 170~180V Nixie Power Supply
• A 20k resistor
• Arduino Uno or any other 5V Arduino
• Multimeter
• Lots of jumper cables

Step 1: Getting started with a Nixie tube

Before you get started, you need to get acquainted with the Nixie tube. Each digit of the tube has an ending pin at the bottom of it. If any of these leads are connected to the ground, the digit will glow; provided the anode of the tube is supplied with 170 to 180 volts. This “ignition voltage” differs for each tube but is generally in this range.

You can easily locate the anode of the tube as it is generally situated at the back, and it’s structurally reinforced. This makes it very distinguishable from the other pins.

WARNING: Do not ever connect your tube between a high voltage source and the ground. 170V+ is very high voltage. Always connect a current limiting resistor between the anode and your power source. 20k is a good value for the IN-14. In any case, proceed with caution!

TIP: A typical female 0.1″ jumper cable should be a tight fit around the Nixie leads, so you can use them to run your initial tube tests.

Step 2: power source

For most nixie tubes, you need a 170V power supply. eBay or Aliexpress should have readily available modules for this.

They are good enough to get started in the Nixie tube hobby but they are generally poor quality and might die very early. Boosting 12V to 170~180V is very taxing on electronic components (MOSFET, magnetics, etc. etc.) and the cheap power supplies are just not reliable enough. Speaking from experience: three of them died from regular usage.

I highly recommend you invest in a quality power supply, such as the one I design and sell on Tindie:

Link to the store: https://www.tindie.com/products/tonyp7/170v-high-voltage-nixie-power-supply/

These kits usually require an input voltage between 5 to 12V, and incidentally 12V is a good value to power your Arduino from the barrel jack and onto the integrated 5V voltage regulator. From a single 12V power source you can therefore power both your Arduino and the Nixie, while maintaining the same ground level. 12V is a popular value for a lot of consumer electronics so chances are you have one of these wall warts hanging around in your home.

Step 3: The Nixie driver

Many companies produced Nixie drivers, but today they are no longer on their catalogs. That being said, you can easily find “new old stock” on eBay or any other place. These chips are 5V logic and transform a 4 bit input (0000 to 1111) into a given output pin. They are more or less a typical BCD to decimal decoder that you can buy today for 7 segment displays; except that they are built in with high voltage transistors.

The pinout is as following:

Known nixie drivers include:

• Texas Instruments SN74141
• MSI DM74141
• USSR K155ID1
• … And many more. A complete list can be found here if you are interested in these chips.

Truth table is as following:

Input	Output
D	C	B	A
0	0	0	0	0
0	0	0	1	1
0	0	1	0	2
0	0	1	1	3
0	1	0	0	4
0	1	0	1	5
0	1	1	0	6
0	1	1	1	7
1	0	0	0	8
1	0	0	1	9

Step 4: Putting it all together -the schematics

Connecting it all together should be an easy task. The difficulty here is the amount of wires: it’s easy to mix up input A, B, C & D of the driver chip since they are in a completely random order (A, D, VCC, B, C –who thought that was a good idea?); and the output to connect to the nixie don’t seem to make any more sense. Proceed with care and you’ll have a working circuit in no time!

Key points on this schematic:

• Connect Arduino pins 10, 11, 12 & 13 to the pins A, B, C & D of the nixie driver.
• You can connect the 12V source directly on the Arduino by using the “VIN” pin and any ground pin.
• Use the same 12V source to power the step up converter.
• Use the 5V pin of the Arduino to power the nixie driver.
• Don’t forget the 20k resistor on the anode of the nixie!

Step 5: uploading the code

Upload this code on your Arduino. Don’t forget to disconnect it to the 12V source first! Having two source input (from the USB and from the external 12V) might damage your Arduino.

uint8_t currentValue = 0;

//Use pins 10, 11, 12 & 13 of Arduino
//Connect to pins A, B, C & D of your SN74141 Nixie driver chip
#define A 10
#define B 11
#define C 12
#define D 13

void setup() {
  pinMode(A, OUTPUT);
  pinMode(B, OUTPUT);
  pinMode(C, OUTPUT);
  pinMode(D, OUTPUT);
  nixieWrite(A, B, C, D, 0);
}


void nixieWrite(uint8_t a, uint8_t b, uint8_t c, uint8_t d, uint8_t value){
  //D is most significant bit
  //A is least significant bit
  digitalWrite(d, (value & 0x08) >> 3);
  digitalWrite(c, (value & 0x04) >> 2);
  digitalWrite(b, (value & 0x02) >> 1);
  digitalWrite(a, value & 0x01);
}

void loop() {
  delay(1000);
  currentValue++;
  if(currentValue > 9) currentValue = 0;
  nixieWrite(A, B, C, D, currentValue);
}

The pins chosen (10, 11, 12, 13) are completely arbitrary and of course can be substituted by the pins of your choice.

One interesting bit about the code is the “nixieWrite” function: it transforms a decimal number into its individual bit components by isolating the bit with a bitwise and operation; then the result is shifted according to the position.

Take number 9 for instance, or 1001 in binary. The result will be:

• D: 1001 AND 0x08 (1000) = 1000. 1000 shifted 3 bits: 1
• C: 1001 AND 0x04 (0100) = 0000. 0000 shifted 2 bits: 0
• B: 1001 AND 0x02 (0010) = 0000. 0000 shifted 1 bit: 0
• A: 1001 AND 0x01 (0001) = 0001. no need to bit shift this one.

Wrap up

… That’s all there is to it! Nixies are fairly easy to use provided you have all the components needed and the patience to painstakingly wire everything one by one. As a single nixie requires at the very least 17 wires (10 for the digits, 6 for the driver’s input including VCC and GND, and one for the 180V anode), it can get rapidly messy.

As a matter of fact, without the IC driver it gets even more messy. You can drive nixie with high voltage transistors such as a BF259 “Bipolar (BJT) Transistor NPN 300V 100mA 90MHz 5W”; but you will need one for each digit!

That being said, there is nothing quite like this amazing orange glow; and all this work will definitely give a unique look to your projects!

Credits

This tutorial would not have been possible without these other great resources:

• http://www.tube-tester.com/sites/nixie/data/in-14/in-14.htm
• http://www.tube-tester.com/sites/nixie/74141-NDT/74141-NDT.htm
• http://www.csgnetwork.com/anoderescalc.html
• http://www.instructables.com/id/How-to-Control-a-Nixie-Tube-with-an-Arduino