The setup consists of a Logic Board and a separate 230VAC Power Board.
This board uses a rotary encoder and the 7-segment display + LED as userinterface. The ATtiny84 handles the timing, userinterface and switches the relais on the power board with a transistor.
This board is mounted isolatated inside the case. It supplys a regulated 5VDC voltage for the logic board out of a 230VAC mains voltage using a LM2940 low-dropout regulator circuit. A 5V relais switches the current for the uv-lamps. A microfuse protects the ciruit.
Little milled coutouts in the pcb should prevent potiential surface leakage between the small contactspacing of the little relais.
The time period can be set between 1 second an 60 minutes. Seconds can be set by rotating the encoder, minutes can be set by press-rotating the encoder.
The count-down timer can be started and stopped by a short press on the encoder. The relais and LED will be controlled accordingly.
A longer press on the encoder starts the count-up timer without switching off the lamps.
A long press stores the time period to the EEPROM for the next exposure and will be loaded on start of the device.
Userinputs are confirmed with little display animation and a tonesequence.