As i am in a process of making a UV LED lightbox these days, i was looking for a convenient timer circuit for an automatic turn-off feature. I found many simple solutions using just one 555 timer and a few components, and many elegant ones using a PIC16F84 and a 7-segment display. I decided to use this circuit that uses a 555 timer and a 4020 counter. The PCB and schematic are in the attachment. The PCB has a few differences than the schematic, but nothing to worry about. I don't have a specific reason for using this circuit, maybe because of it's versatility or something else, i just liked it when i saw it.