Nixie Tube Clock: Retro Display Build Guide India

The Nixie tube clock is the ultimate retro electronics project — glowing orange digits floating inside glass tubes, powered by 1950s technology. This guide covers the complete build process, from sourcing tubes in India to safely handling the 170V DC power supply.

What Are Nixie Tubes

Nixie tubes are cold-cathode gas discharge tubes. Inside each tube, 10 metal cathodes shaped like numerals 0-9 are stacked. When energised at approximately 170V DC, the surrounding neon gas glows warm orange.

• Operating voltage: 140-180V DC
• Current draw: 2-5 mA per tube
• Lifespan: 200,000+ hours (over 20 years continuous)
• Aesthetic: Nothing compares to the warm analogue glow

Sourcing Nixie Tubes in India

Nixie tubes are no longer manufactured. Options in India:

• IN-12 and IN-14 (Soviet): Most common. Rs.300-600 per tube from surplus dealers.
• Indian surplus: Check Lamington Road (Mumbai), Lajpat Rai Market (Delhi), SP Road (Bengaluru).
• eBay/AliExpress: Matched sets of 6 for Rs.2,000-4,000.

Always buy matched sets from the same batch for consistent brightness.

High Voltage Power Supply Design

Generate 170V DC from safe 5V/12V input using a boost converter:

• NCH6100HV module: Purpose-built. Input 5V, output adjustable 100-200V DC. Rs.300-500.
• Custom boost converter: MC34063 or NE555 + MOSFET + inductor + diode.
• Pre-built 12V to 170V modules: Safest option for beginners.

Driver Circuits: SN74141 and K155ID1

You need a Nixie driver IC to switch 170V:

• SN74141: Original BCD-to-Nixie decoder. Rare and expensive today.
• K155ID1 (Soviet equivalent): Widely available, Rs.100-200. Functionally identical.
• HV5122/HV5222: Modern high-voltage shift register — no multiplexing needed.

Arduino Control and Multiplexing

Arduino Nano controls the clock with multiplexing:

void setDigit(int tube, int digit) {
  digitalWrite(ANODE_PINS[tube], HIGH);
  digitalWrite(BCD_A, digit & 1);
  digitalWrite(BCD_B, (digit >> 1) & 1);
  digitalWrite(BCD_C, (digit >> 2) & 1);
  digitalWrite(BCD_D, (digit >> 3) & 1);
  delayMicroseconds(2000);
  digitalWrite(ANODE_PINS[tube], LOW);
}

Multiplex at over 100 Hz for flicker-free display. Add DS3231 RTC for accurate timekeeping.

Building the Clock Step by Step

1. Design the PCB with tube sockets, driver ICs, Arduino Nano header, boost converter
2. Build and test the power supply for stable 170V under load
3. Test each tube by cycling through all digits
4. Programme the clock with time display, date display, transition effects
5. Build the enclosure — walnut, acrylic, or 3D-printed cases look excellent
6. Add auto-brightness (LDR), anti-cathode-poisoning routine, alarm function

Safety Precautions for High Voltage

170V DC is dangerous. Safety rules:

• Never work on the circuit while powered
• Use a discharge resistor (10k ohm, 1W) across the high-voltage rail
• Cover all HV connections with heatshrink tubing
• Keep the finished clock in a sealed enclosure
• Use proper insulation between HV and LV sections

Modern Alternatives: Nixie-Style LED Displays

For a safer alternative, build a retro-style clock with these modern components: