Finding your tent in a large festival or campsite can often be pretty tricky! Miles upon miles of similar looking tents, dark paths between them and as often as not (for me at least) a beer inside you to fuddle your tent finding prowess.

Enter the festival tent finder! This super simple circuit, when strapped to a mobile phone, detects the illumination from a mobile phone backlight and turns on a small battery powered relay. This relay can be used to turn on a set of battery powered LED lights fastened to your tent.

All you need do to find your tent, is phone it! When the phone in your tent rings, the lights will turn on. Easy!

This project is a collaboration* between Kiteman and myself.

(*Kiteman adds: I had the basic idea ("Wouldn't it be cool if you could phone your tent to find it?"), but Jayefuu did the actual work designing and building the circuit. I had something much less elegant, and more expensive, in mind.)