UV Timer
My UV exposure frame for making PCBs did not have a timer, so I built a little one and included it in the housing.
It simply turns off the light after a certain time. Of course nowadays PCBs can be ordered for a couple of bucks online making it widely available for hobbyists even with small budget.
I used some old mechanical encoders to set the time. It seemed the most practical because you can see the settings without energy being applied (e.g. a 7-Seg display).
The circiut was then built into the frame with a status LED.
