Using UV exposure technology is common way of building PCB at home. If you tried this, you probably know that exposure timing is very important to get precise image on photoresist. Overexposure or underexposure always lead to failure. So it is best to leave timing for timer. If you built your own UV box, then you should also build a timer.
Diyfan suggests simple PIC16F628A based timer project. It is really simple – 2×16 LCD displays time and status. Three push buttons allows to select time, start timer and stop timer. It also has speaker to play sound alarm when time runs out. Circuit simply send signal to a pin which can be connected to relay of your choice which then controls the lamps. Of course it can be used for other purposes including motor drive for some time, water sprinkler and other.