This timer was initially designed for the UV-Exposure Unit. However, it proved to be extremely useful for providing controlled "on" times for other equipment such as photo-enlargers, developers, small heaters, incandescent lamps, fluorescent lamps, etc.
3 - Digits Count Down LED Display
"On" -Time adjust potentiometer
"On" - Indicator - LED
"Idle" - Indicator - LED
1-SPDT Relay / 1A-250V
1 Digital Input Port - which optionally can be connected to a "safety" switch. This input triggers the auto pause of the timer for safety reasons.
Power Supply: 9-15V / 100mA
0-999 sec Timer electronic schematic
Firmware (hex file)
The Printed Circuit Board details and the Source Code in C for this project (paid-downloads)