In 2024 I’ve made a small model of a construction site light tower and generator. I forgot to make a post about it here, so here it goes.

At first glance it looks like a rather simple scale model, just with fine details. However, the light tower is functional, and has a trick up its sleeve - it only turns on when you "attach" a generator to it.

The generator is, in fact, just a magnet, and the tower contains all the power and logic. The power supply is a small Li-Ion battery (from TWS headphones), and the "logic" is a reed switch that turns on when the magnet is close. The size of the magnet is chosen so that it triggers the switch when placed on one side of the tower, but on the other.

The idea is that these models should be transported by an RC truck across the diorama, unloaded on site, and then the operator could turn the lights on, all remotely, using only a manipulator crane.

Further idea is to use magnetic sensor IC instead of a reed switch, for footprint reduction. The sensors are available in SOT23 package, for example. You can read more about those in this post.