One object I could not find last June in Friedrichshafen Ham Radio fair is a Geiger-Muller counter. What for? Mainly for curiosity of measuring if my home is radiation free given the amount of surplus around. And a Geiger counter can be re-sold easily afterwards. Failing my purchase, I started an online quest for an alternative.
First I came across a small dongle that plugs into a smartphone earphone/mike hole. It is made in Korea and costs about 30 EUR/USD, with an accuracy of ~30%. Few days of thinking later, I remembered an article on Hack A Day blog about an Android and iPhone app that acts as a Radioactivity Counter (that's the app name). It works by counting how many pixels of an obscured camera sensor turn white because of a high energy particle passing through (beta and gamma).
That's cool! Just need to cover the camera sensor area with thick black paper and let the app run. Fine. Almost no readings around home. It is a good sign, but I need a proof that it works when there is a radiation going on.
So, I have been looking for something that you would never want to find in your life: a beta/gamma radiation source. It is a paradox: you look for something and you hope to never find it! Granite, dangerous energetic jewels, ... all something that I would have to dispose properly afterwards. Then I came up with a different approach.
The most easy way to expose a smartphone to ionizing radiation is to get it X-rayed at some security checkpoint. I realized it when entering the Milan Expo 2015, but the lens was not covered (this "source" is even written on HaD post, right on top!). Too late. Next chance would be an airplane trip to Berlin.
Been there, done it.
Results in the next post!