A simple PIR (Passive Infra Red) motion detector
Basic motion sensors are surprisingly small and fiddly. They need to be connected to GPIO pins on the Raspberry Pi which you can do using simple leads that push into place, or you can solder joints for a more permanent connection. Soldering is also fiddly.
Once you have your wiring in place (ensuring that you get the connections correct to avoid power surge and subsequent sensor meltdown) you can write some python code to interrogate the status of the GPIO pins and find out if the sensor has sensed anything. If it has – bingo, you are on your way. What would you like to do with this information? Now you are back on terra firma and *just* have to do some creative coding that responds to the movement. Game on.
The sensors that I tried were only moderately or intermittently sensitive. Sometimes it seemed as though you could dance a waltz in front of them and nothing would happen, other times the merest twitch would set them off. This made it difficult to generate consistent responses for even relatively simple scenarios, such as the presence or absence of a viewer in front of the sensor. For more complex scenarios, such as detecting when the viewer is moving away from the sensor, the success rate was lower still.
