SURI - Radiation Measuring Robot

SURI (Sugárzásmérő Robot, or Radiation Measuring Robot) is a LEGO Mindstorms NXT based robot that measures radioactivity. Its sensor is a Geiger-Müller tube from a handheld Geiger counter we took apart. The beats from the tube go into its own circuit and from there through a small amplifier into one of the NXT’s sensor inputs, where an NXT-G program counts them for a minute. The tube sits on a gear driven by one of the motors, so it can be swung around a horizontal axis: pointing forward to measure a room from different angles, or pointing at the floor for mapping. Because two NXTs can talk over Bluetooth, the counts can also be sent to a second NXT, so the person measuring can stand tens of metres away from wherever the radiation is high.

Getting the numbers into a computer was the tricky part. The NXT has no port a PC can read easily, so we built a LEGO-compatible optocoupler, an LED and a photoresistor stacked inside bricks, from a motor output to the game port. The second NXT receives the robot’s measurements and sends the value bit by bit as a binary number. The MSW Logo program on the other end collects them in a list and draws charts from them.

We did three kinds of measurements with SURI: one focusing on how the radiation changes with the angle of the tube, one comparing different building materials, and one drawing a radioactivity map of an area from a central point. István Nickl built the robot and I wrote the NXT-G and MSW Logo programs, after school, mentored by our teacher Ágota Lang. We entered national high school competitions with SURI and won first prize at the TUDOK conference of the Hungarian Research Student Association and first prize of the Metropolis award of the Természet Világa (World of Nature) journal.