Geiger Counter + Display

Backside of Geiger Counter board

I finally managed to hook up a cheap Nokia display to my Geiger counter. I built that Geiger Counter myself @28C3. Kits are still available from MightyOhm – good stuff.

This week I got this nice little display from here (thanks Lenni). It’s easily controlled – there is even an Arduino Tutorial. Interestingly its a graphic display – so there are plenty of logging options – in theory. Because the Geiger Counter runs with a ATtiny2313 – which has 2k of Flash. And most of that Flash is already used by Geiger Counting code. So the Ardunio Tutorials Character Set takes about 350 % of the ATtinys Flash.

I created my own tiny font (5×3 pixels = 15 bit ~ 2 bytes per character). Well – the “M” is not really well depicted in 5×3 pixels – as you can see in the images: first line says: “26 CPM S”. All the serial output code was kicked – and display code fitted in. Luckily there are also plenty of unused pins on the ATtiny. I reused ISP pins and the unused pins – so the display is connected to just Port B which makes things even easier. After some solder work the display was nicely connected.

Geiger counter with working display

The output was buggy first – I finally found out, that the moving average buffer some got corrupted in the upper bytes – reducing it’s size to 30 bytes = 30 seconds resolved that issue.

Code is available at github.

Todo:

• Calibrate the thing – hopefully I can convice my medical physicist to help me…
• Correct for Dead time
• enable PWM for backlight – in order to dim backlight and safe energy
• switch/dim backlight via button
• log max values
• Graphs!