dynode.nl

Above is a picture of my recently (practically ) finished project. It is a sort of weather station which measures light, temperature, relative humidity, atmospheric pressure, and of course radioactivity!

The core of this setup is the excellent DIY Geiger Counter PCB by [Brohogan]. This kit is a geiger counter circuit combined with a standalone Arduino circuit. Most people buy this kit, connect an LCD and put it in a nice box. Because the Atmega328 pins are broken out via handy pin sockets it is very easy to connect any additional components and/or sensors to this PCB.

I also have one PCB in a box, but I wanted to measure radioactivity outside to see variations with time and rainfall so I bought another PCB. I designed a housing to hold the sensors, PCB and cabling and protect it against moisture. The Stevenson screen holds the sensor PCB and is made from plastic plates attached to eachother with stainless steel bolts and nuts. It exposes the sensors to the outside air while keeping everything dry and out of direct sunlight. The whole setup is also painted white to minimize solar heating, this is especially important for measuring accurate temperatures.

The PVC tube holds the cabling (separate cables for the sensors and the geiger tubes HV supply and return) which ends up in the bigger piece of PVC tube which houses the PCB and it’s “shield”. This shield is made of perfboard, has pin headers to connect to the geiger counter PCB, and has a bunch of PCB screw mounts to connect the cable running from the sensor PCB.

Both the sensor and geiger counter PCB are wrapped in self vulcanising tape to keep everything sealed against bad weather. On the sensor PCB, the actual sensors are kept uncovered of course. The sensor board also holds two GM tubes wired in parallel to combine their output.

The “weather station” connects to my server with 10 meters of UTP which carries 5V, ground, TTL RXD and TXD signals and a reset line for remote reprogramming. Data transport seems to work fine, I still have to test reprogramming. Connected to the cable is a FTDI USB to TTL adapter which supplies the 5V, data and reset lines.

The setup is now live for testing purposes. I will later move to the roof where it will hopefully function for a long time.

Current graphs can be found at http://utr.phoropter.nl/graphs/ The light, pressure and radioactivity graphs are from the described setup.

Logging and graphing the output is done by bash shell scripts and cacti, I will try to describe them later and also include the Arduino source code.