Stackable 8x8 neon indicator bulb display

What is it?

The NeonMatrix 8x8 matrix uses common neon indicator bulbs to display simple graphics.
They can be chained and controlled directly via SPI.

Operating voltage is about ~70V AC.
The circuit is pretty dangerous, all neon bulbs have high voltages on their legs, the 74HC595 shift registers are floating at mains/AC potential.


PCB, with 8x8 neon bulbs PCB, with 595 shift registers, ESP32 next to it

Hack: Audio amplifier inverter

To generate a (mostly) safe high voltage neon supply, a 50 Hz mains transformer can be connected (in reverse) to the output of an audio amplifier. By playing a 50 Hz sine tone, the transformer outputs a variable high voltage:

audio amplifier, connected to a reversed mains transformer