I then had to think about lighting so I developed an Arduino based lighting system. The Arduino samples the external lighting levels using a lDR resistor circuit, the Arduino reads the voltage on the pin and completes an A to D conversion and then automatically adjusts the led light in the nestbox to follow the external lighting levels . This system has been used for a number of years and has proven not to bother or upset any nesting birds. The only change has been to move to using encapsulated LDRs on extended cables mounted on the exterior of the nestbox.
The nest boxes are powered by 12v leisure batteries which are charged by folding solar panels. The whole systems uses 4.2 watts so the battery can easily be replenished on bright sunny days. You need enough charging power from the panel to cover the night time operation which can prove difficult with cloudy dull weather which means the system does go offline from time to time as the controller turns off the supply to divert. energy to charge the batteries