Circuit schematic

In my latest version of my 6 digit Nixie tube clock I decided to use a few different ICs to give some advanced functionality.

I decided on an esp32-wroom-32e as the micro controller, planning on implementing Bluetooth functionality, as well as more processing power for other features.

I added an AM/FM radio IC to give the clock an authentic analog radio experience, as well as a dedicated DAC and amplifier which is more powerful than the inbuilt DAC on the esp32.

I started by designing the circuit schematic using KiCAD 9, I’ve since added/tweaked some parts of the schematic but these were purely for circuit routing. The schematic can be found below:

The power supply is powered by USB type C which is configured to provide 5V 3A. To power the esp32, a 3.3V voltage regulator was added, as well as an LM2577 circuit to produce 12V as the first stage to be passed to the high voltage power supply. The high voltage power supply provides 180V DC using a MAX1771 IC.

The main schematic shows the esp32 and the Nixie tube driving circuit. The esp32 has a USB to UART IC to enable programming the clock from the same USB port as the power circuit, as well as a GPIO extender since the circuit uses more I/O than the esp32 can provide.

The Nixie tubes are driven by a single K155N1 IC and are multiplexed using transistors driven by the esp32. This was done to save on circuit complexity and board space, as 6 tubes + 4 bulbs can be a lot of wiring!

The final sheet of the schematic shows peripheral devices and special features such as the AM/FM radio circuitry, 2x rotary encoders for user input to control the volume, channel, and settings, and 6x addressable RGB LEDs (1 for each Nixie tube).

All in all this circuit schematic should hopefully produce a well rounded Nixie tube clock with a wide range of features. I’ll be sharing the PCB design later.

If you have any questions about how I designed this circuit please reach out and I’ll be glad to have a chat.