A touch screen Geiger counter without a Geiger tube

geiger

We’re assuming [Toumal] was desperately bored one day, because in the depths of the Internet he found some really cool components to build a solid state Geiger counter.

The Arduino and touchscreen are rather standard fare [Toumal] picked up on eBay for about $30. What really sets this project apart from all the other geiger counter builds we’ve seen is the solid state geiger counter [Toumal] used. This device uses a specially-made photodiode made by First Sensor to detect gamma emissions from 5 to 1000 keV.

[Toumal] put all the software for his Arduino touch screen radiation detector up on github. To be honest, we’re really impressed with the rad sensor [Toumal] used for this project, so if you ever decide to pick one of those up, he’s got your back with an Arduino library for it.

A very tiny gamma ray detector

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When you think of a radiation detector, you’re probably thinking of a Geiger tube and its high voltage circuitry. That isn’t the only way to measure gamma radiation, though, and [Alan] has a great circuit to measure even relatively weak radiation sources. It uses a very small photodiode, and draws so little power it’s perfect for projects with the smallest power budgets.

The detector circuit uses a miniature solar cell and a JFET wired up in a small brass tube to block most of the light and to offer some EM shielding. This, in turn, is attached to a small amplifier circuit with a LED, Piezo clicker, and in [Alan]’s case a small counter module. The photodiode is actually sensitive enough to detect the small amounts of gamma radiation produced from a smoke alarm americium source, and also registers [Alan]’s other more powerful radioactive sources.

The circuit only draws about 1mA, but [Alan] says he can probably get that down to a few micoAmps. A perfect radiation sensor for lightweight and low power applications, and gives us the inspiration to put a high altitude balloon project together.

Gamma-ray scintillation probe in a paint can

gamma.ray.scintillation.probe.in.paint.can

The [Prutchi] family sounds pretty cool. [David], the father, is a well educated engineer, has 70 patents, and has written two books. On his off time, he has a passion for making experimental physics accessible to the average Joe. His daughter [Shanni] is a high school student who co-authored one of those same books, and helps conduct research in the fields of Radio-Astronomy and Quantum Physics. Together, they came up with an affordable, yet very sensitive, gamma-ray scintillation probe for their customized Civil Defense V-700 radiation survey meter. Sweet.

They decided to use parts that were low cost and readily available so others could easily follow in their footsteps. A Philips XP5312/SN photomultiplier tube (PMT) and scintillation plastic are the main components.  The enclosure for the probe is a standard paint can, lined with polyurethane foam inserts to help protect the assembly and hold everything in place.

[David] says that since the probe is very portable and has a high level of sensitivity, it is an ideal candidate for radioactive mineral surveying and scouting miscellaneous gamma-ray sources. They documented the whole process and have compiled a handy PDF file for those who are interested in creating their own.