Turning a phone into a Geiger counter


We’re no stranger to radiation detector builds, but [Dmytry]’s MicroGeiger prototype is one of the smallest and most useful we’ve seen.

The idea behind the MicroGeiger comes from the observation that just about every modern smartphone can provide a small bit of power through the microphone jack. Usually this is used for a microphone, but with the right circuit it can be stepped up enough to power a Geiger tube.

[Dmytry]’s circuit uses a hand-wound transformer but keeps the part count low; there’s only a few dozen caps, resistors, and diodes in this build, making the circuit much smaller than the Geiger tube itself.

Since [Dmytry] is powering a Geiger tube with a phone, it only makes sense that he should also record clicks from the tube with an Android app. Right now, the entire project is still in the prototype stage, but everything works and his app can detect radiation from one of [Dmytry]’s sources.

The code and schematics for the MicroGeiger are available on GitHub, with a video of the project in action below.

10 thoughts on “Turning a phone into a Geiger counter

    1. Good grief… As trndr pointed out it’s that phone that’s counting when a particle causes the GM tube to conduct. Yes the phone powers the tube, but this is not a project that where the phone proved the power & and other additional circuitry displays the results.

  1. Far out. In the event things really go to hell this may be feature built into every phone, a step towards to a tricorder for everyone. In the mean time I’d settle super bright LED to use a flashlight on every cell phone.

  2. Didn’t somebody make his iPhone to a scintillation counter by putting some stuff before the lens of the camera?
    That would’ve really been using the phone as a detector. This is “just” amplification, but nevertheless still pretty cool think! Didn’t know that u can step up that much to drive an Geiger tube.

  3. Hi guys. Glad you like my circuit. I have written a page documenting the project here: http://dmytry.com/electronics/microgeiger.html . It is also possible to go without winding your own transformer (pretty much), by winding those low turn count primary winding onto a 3.2 mH inductor salvaged from a compact fluorescent lightbulb (the one that uses a pair of E cores), but then you will need extra multiplier stages (2 extra diodes and capacitors) and it will be somewhat bigger… I have an earlier prototype that works fine in such a manner – perhaps I should post a variation of the base circuit which uses that. Though, winding your own transformer is really easy at that size – you can use a power screwdriver. I’d say that winding the transformer was one of the easiest parts of the project.

    Also, there’s a minor error in the circuit diagram that is shown in the video (and used in the title post) – the 3.3M resistor should connect to the microphone jack. Mixed up this stuff when transcribing the circuit to computer.

    Also, about me: I am a videogame / 3D special effects developer.

    1. Ohh, and the electronic component count is 18 exactly, including the transformer. If you are feeling adventurous, it can be brought down to 16 with a slight tweak to the transformer (I could eliminate the voltage doubler but then it’d just barely make enough voltage and may not work well at high CPM), 15 with a 400v Zener in place of 2x 200v Zeners, 13 if you twist a wire around tube anode wire instead of the C6 and R6 but that’s cheating and might be bad for your phone (it worked like this in one of the earlier prototypes though), and 12 if you tweak the R4 to obtain 400v with your phone without the Zeners, but then it may likely work incorrectly with other phones and/or fail to provide enough voltage at high CPM.

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