Sunday, October 16, 2011

Homemade Geiger Counter - Part 2 -- The hardware

Homemage Geiger Counter - Part 2 -- Hardware build

The main objective here is cheap and some what accurate.

Allow me to clarify this point. Reversed biased PN junctions(avalanche photo-diode et el) are very desirable as a Geiger counters
* They are cheap to mass produce using common manufacturing processes.
* If the circuitry and PN diodes are well chosen then the counter can be more accurate and faster than a Geiger tube or even scintillation crystals.

The problem is post Fukushima Geiger counters where in such high demand that anything that ticks in the presence of radiation was acceptable. Basically all of these are PN junction based devices, that are badly slapped together devices rushed out to a sellers market. What is worst is that these cheap devices where selling up of 500 USD a pop shortly after the event. A quick check of amazon shows me that the same models are now selling at around the 200 USD mark after having peaked at around 1500 USD!

I figure if I going to get crap it may as well be crap i have created for 1/15 of the price. So the device I have is around the 100 USD mark with usb and networking capabilities.

I used a Kited setup that the Tokyo hacker space member Akiba put together.

It involves an Ardiunio base board called Chibi(bottom in the picture). And a second shield they called a NetRAD(top in the above), which is basically a board with a LAN networking chip and the Geiger counter circuitry.

The final shield is an LCD and button. As you can see it was just hacked together with a cheap a prebuilt 600yen LCD board and a pull up switch.

The NetRADs specs are here And the Dev history of the board is here. It makes for a very interesting read.

A fuller set of picture are visible here

I was hoping to do a full tear-down of the device but I simply can't seem to get the time.

I have also noticed the device seems to have a wide working range, a series of readings can vary by any thing upto 100% from the average. If this is due to the nature of radioactivity or something iffy in the Geigers power supply I don't know. Besides this the device is still excellent. The readings still average out to a stable reading over a 10min period.

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