He started out using an open source multichannel analyzer (MCA) called Theremino. This connects through a sound card and runs on a PC. However, he wanted to roll his own and did so with some simple circuitry and an Arduino.

The tube detects very faint light in the crystal so they need to be in a light-tight enclosure. The Arduino needs a little help to read the pulses from the tube in the form of a simple circuit. The circuit acts as a peak detector and the peaks last only about twenty microseconds. The post doesn’t have the schematic for the peak detector but the video, seen below, does.

If you want a run down on spectrometer projects, check out Hacklet 122. Admittedly, most of the ones we see rely on visible light.