Countdown timer can count fro m1 second up to 99 minutes and 59 seconds. Ideal tool for PCB maker when need to control PCB exposure with ultraviolet light. Timer is equipped with alarm when countdown finishes.
Timer has it own power supply unit, so you can plug it to AC outlet and start counting. The counter is based on old good PIC16F84 which counts time and drives 4 seven segment LED displays. Timer can be controlled by three buttons. One Starts/Stops timer, second sets time for each of digits, and last button allows to select preset times from EEPROM-convenient for quick time select. Project files are available for download.