Sun Tracker

This is something my son and I used as a sun tracker. The basic idea is that you hot glue four light sensors (we used photo-resistors) in each quadrant, and as the light moves off-center it casts shade on the opposite side. So maximizing the value of all the sensors will have it point to the brightest spot.

The design includes slots to drop in the sensors and allow the leads to go out the back. It also includes a hole down the center, which can be used to calibrate. (The light coming down the center hole will project a circle when pointed directly at the light.)

I've built it at various heights. A taller one is more sensitive to tiny changes in angle, but can cause a lot of "seeking", while a shorter one is more forgiving but less sensitive. Black filament works best to avoid reflections.

I've also included my Arduino sketch which may be a bit of a naive approach, but worked for our purposes. (This sketch and typical photoreceptors causes quite a bit of "seeking"