This counter can be used to switch on an electrical appliance (or other loads) for a preset duration. The ranges are : 1 ~ 99 sec. or 1 ~ 99 min. (Note : 99 min = 1 hour 39 min.).
Timing unit of SEC. or MIN. can be selected. Pressing the "Start" button the relay is on and the counter starts to count down.
The 7-segment shows remaining time. When the display reaches zero, the relay is off and buzzer sounds
Applications : Darkroom timer. Egg timer, .... PIC 16C54 datasheet