nixiedisp - nixie tube display & clock

nixiedisp in clock mode

Table of Contents


Nixiedisp is a 6-digit nixie tube numeric display, software-controlled over USB or RS232, that also functions standalone as a clock.


git repository:


Copyright (C) 2020-2021 John Tsiombikas <>

All hardware designs and software in this project are free. Feel free to use, modify, and/or redistribute under the terms of the GNU General Public License v3, or at your option any later version published by the Free Software Foundation. See the full license text for details.


nixiedisp rev2 schematics (PDF)

main schematic nixie tube drivers schematic power supply schematic
mainnixie tube driverspower supply

Printed Circuit-Board

nixiedisp rev2 gerbers (for PCB manufacturing)

PCB front copper layer PCB back copper layer
front copperback copper

Bill of Materials

The BOM is available in CSV or open document spreadsheet format.

I have included mouser product ids to make it easy to order the components. Simply upload bom.csv to the mouser BOM tool, designate the quantity and mouser-id columns, and add everything to the cart. It's worth going over every item and changing the quantity to something that makes sense though. Mainly to have spares, but also because buying a single 0805 resistor is ridiculous.

#DescriptionFootprintMouser ID
1CR2032 battery holderSMD battery holder Keystone 1060534-1060TR
150.1uF capacitorSMD 0805581-08055C104K
222pF capacitorSMD 080580-C0805C220K1HACTU
12.2nF capacitorSMD 0805187-CL21B222JBANNNC
51uF electrolytic capacitor (RS232 option)SMD electrolytic 4x5.4710-865060640001
20.33uF electrolytic capacitorSMD electrolytic 4x5.4710-865230640003
1220uF low-ESR electrolytic capacitorSMD electrolytic 8x10667-EEE-FP1V221AL
110nF capacitorSMD 0805187-CL21B103JBANNNC
12.2uF 250V electrolytic capacitorThrough-hole radial647-UVR2E2R2MED1TD
11N4148 diodeSMD SOD-323 (0805)750-1N4148WS-HF
1MUR160 diodeSMD DO-214A (SMB)821-MUR160SR5G
1DB9 male connector (RS232 option)Through-hole DB9 male523-L717SDE09P1ACH
1Micro-USB connectorUSB Micro-B Molex-105017-0001538-105017-0001
1AVR programming header2x3 male pin header 2.54mm pitch710-61200621621
1DC barrel jackbarrel jack 2mm center pin490-PJ-202A
1Hour-separator LED connector1x3 female socket 2.54mm pitch538-90147-1103
1power jumper/switch header1x2 male pin header 2.54mm pitch538-22-28-4112
1220uH inductorSMD inductor 14x18.3652-SDR1806-221KL
2MMBTA55 PNP transistorSMD SOT-23863-MMBTA55LT1G
66MMBTA42 NPN transistorSMD SOT-23863-MMBTA42LT1G
410k resistorSMD 080571-CRCW080510K0JNEAC
6647k resistorSMD 0805652-CR0805FX-4702ELF
6160k resistorSMD 0805660-RK73H2ATTD1603F
31 ohm resistorSMD 0805603-RC0805FR-071RL
21k resistorSMD 080571-CRCW08051K00JNEAC
624k resistorSMD 0805660-RK73H2ATTD2402F
1475k resistorSMD 0805667-ERJ-6ENF4753V
13.32k resistorSMD 080571-CRCW0805-3.32K-E3
1Right-angle tactile buttonSMD right-angle113-TA34W2VTR
1Atmega328PB-AU microcontrollerTQFP-32556-ATMEGA328PB-AU
674HC4514 demuxSOIC-24 wide771-74HC4514D-T
1MAX232 level converter (RS232 option)SOIC-16595-MAX232DR
174HC126 3-state bufferSOIC-14595-SN74HC126DR
1DS1302Z+ RTCSOIC-8700-DS1302ZT&R
1MC34063AD switching controllerSOIC-8595-MC34063ADR
17805 voltage regulatorSMD TO-252-2 DPAK863-MC7805CDTRKG
1MCP2221AxSL USB interface ICSOIC-14579-MCP2221A-I/SL
374HC164 shift registerSOIC-14771-74HC164D-T
114.7456MHz crystalSMD crystal ECS CSM3X 2pin 7.6x4.1mm815-ABLS7M-14.745B2T
132.768KHz crystalSMD crystal 2-pin 2x1.2mm (alt.footprint Y3)815-ABS0632768KHZ61T
132.768KHz crystalThrough-hole crystal 3x8mm (alt.footprint Y2)695-CFS-20632768EZBB
2Amber 3mm LED (hour sep.)Through-hole 3mm LED859-LTL-1CHA
6IN-14 nixie tube

You don't need both of the 32.768kHz crystals in this list. They are just alternative footprints. You should only populate one or the other.

Also, all items marked as (RS232 option) can be omitted if you don't need the serial port, in which case skip them, and also install a 10k pull-up resistor across the J7 pads (marked usbpwr on the silkscreen). The opposite (having only the serial port and no USB) should also be possible by leaving the USB connector and the MCP2221 chip unpopulated, but that's currently untested. Let me know if you try it.

With current (Feb 2021) prices, without the nixie tubes, these components cost around 30 euros.

ИН-14 (IN-14) nixie tubes obviously cannot be purchased through electronics distributors in the 21st century, but they usually go for around 10-15 euros each on ebay, desoldered from old equipment. Make sure the left-side decimal point wires are intact, because nixiedisp uses them. Some sellers have tubes with the decimal point wires cut very short.


The git repository contains only source code. If you want pre-compiled firmware images, you should download one of the official release archives.

To program the AVR microcontroller with the nixiedisp firmware, you'll need an in-system programmer with the standard AVR 6-pin programming header.

Host-side Software

Under the sw/ directory of the project you will find various programs and scripts that can be used to manage the nixie display through USB or a serial port. Among them is a graphical tool called nixiedisp-gui which can be used to configure device settings, set the time and date for the clock mode, and more.


The git repo contains only source code, but you can download one of the release archives, which includes pre-compiled binaries for various systems.

3D-printed enclosure

A partial 3D-printable enclosure is included (base.stl), which covers the bottom of the PCB where most of the potentially dangerous high-voltage parts of the circuit are located, and also acts as a base for the device. Only a very small area of the top of the PCB has high voltage present, for extra safety a small cap which clips into the side of the enclosure is also included (hvcover_cap.stl).

If you intend to use the board without the bottom cover, an alternative version of the top-side high-voltage cap is provided which protrudes slightlty and clips onto the side of the PCB instead (hvcover_pcbclip.stl).

Download nixiedisp rev2 enclosure: contains OpenSCAD source code for the main part, Blender file for the top-side HV-cap, and pre-generated ready-to-print STL files for both parts.

enclosure CAD view enclosure photo