Combined timer, counter & frequency meter

摘要

This circuit provides an up/down timer, an up/down counter and a frequency meter in one package. It is based on an AVR ATmega8 and a 16x2 alphanumeric LCD. The timer and counter share an alarm system consisting of a speaker which can play a melody and a blinking alarm LED (LED2). Each function can be selected by operating its associated switch (S3-S7).