My DIY scrap Geiger Counter radiation detector: Another writeup

Since my last writeup on a project went over well, I'd like to write about another one of my projects on hackaday. This will be on the homemade Geiger counter I pieced together last winter to serve as a crude backup to my CDV-700 counter. This device costs around $15 to make and can reliably detect X-ray, gamma, and high-energy beta radiation with somewhat usable sensitivity. In short, it will pick up most mildly radioactive objects, such as uranium samples, Am-241 smoke alarm sources, and sketchy negative-ion-radiation-blocking-stickers-that-totally-don't-contain-thorium on Ebay.

Once again, this project is actually pretty simple. I have the tendency to mess up tiny things on big soldering projects and then get distracted and never finish the project, so I used a lot of salvaged components instead of going on Digikey and making a circuit from components.

The heart of the device is a SI-3BG geiger tube, sourced from Ukraine. Mass-produced at the end of the Soviet Union, they are now about $5 on Ebay. These tubes aren't that great, but they do work well and at a bargain price. A geiger counter works by applying high voltage (400-800V typically) to a tube of pressurized gas, which then allows pulses of current to pass through the tube when ionizing radiation strikes and ionizes gas inside the tube.

I used a disposable camera flash circuit to power the tube. You may have seen these used to create really bad stun guns in the past. The flash circuit produces around 300V off of a 1.5V battery. The tube didn't work on 300V, so I added another battery to double the output voltage (thankfully not damaging the circuit) and removed the large bulk storage capacitor to prevent some very painful electrical shocks. The result is a somewhat steady 600V power supply small enough to fit in your hand (not recommended). Applying this to the tube worked as expected, and after running the output signal through a transistor to trigger a surge of current to an audio jack port I found in a dollar store speaker, the device can actually detect radiation! Invisible particles such as beta/gamma radiation from radioactive decay and atmospheric muons generate clicks in whatever set of headphones you plug into the counter.

I packaged the whole thing up in a metal power supply box I pulled out of an old printer and used way too much hot glue to hold everything down. I also clamped the switches on the HV supply down and added my own switch to the front. The final result is a dirt-cheap, extremely-crude-but-working geiger counter (far cheaper than you could buy online) that can output audio to any headset. I've used it to detect a wide variety of radioactive sources. I run it on 2 AA batteries from the dollar storage, so power is easy to obtain and cheap to use. If you need something to pick up radiation and have very little money to spend, this could work. If you want a real reliable detector, I recommend the CDV-700 (used on Ebay of course).

Expect more project posts soon as I have just finished a very heavy quarter at university. Read more about this project here: https://hackaday.com/2017/01/18/a-no-solder-scrap-bin-geiger-counter-for-15/

If you'd like to contribute to my radiation/high-voltage experiments, my various crypto addresses are posted below. I appreciate any donations!

ARK: AXQN61RkAPsJXAkv17YipQKk4MQZCMAUJF

BTC: 1MV7pvR9PGzYBMbSpAyRQbMBonJxZyBnrT

VTC: Vi9o5HMgzwqDEnhVZTksCNRy3JxeatNkQr

Thanks for reading!