Light Dependant Nest Box Lighting.

The white LEDs in nest box are switched during the day on by a mains timer. However these have proven unreliable and to prevent the lights accidentally coming on at night (the bird will leave the next box) the followingcircuit was developed that only allows the lights to be on when its bright outside. The (free) TinyCAD file is here in case you want to modify it (and you could email me any improvements!).

One fail safe feature is that if the LDR becomes disconnected the lights will go off.