[Andy] demonstrates building an ultrasonic anemometer using a cheap after-market parking distance sensor kit and an Arduino. Demo video after the break. Aside from the price, these kits have the ...

The system is controlled by a pair of sensors in the paper which serves as the parking lot ... gate this completes a circuit instructing the Arduino that there’s a vehicle in position.

I recently had to build an infrared close proximity sensor that could tell if something was dropped in a parcel delivery drop box. After some searching, I ended up using a microcontroller ... Here is ...

Of course you can use multiple sensors and outputs to trigger different effects depending on your needs. The Arduino is capable of driving small loads like an LED without extra components.