This topic presents one of the counter applications that can change its state in either direction, under control of a falling edge and raising edge. Given here can count numbers from 0 to 9999 in up and down modes depending upon the state of the selector in the software. It can be used to count the number of rotations per second in a motor i.e. speed. It can also be used as a metal detector and it can also be used at gates of parking areas and other public places.
This circuit divided in two parts: sensor and counter display. The sensor would detect the Metal and provide an input to the controller which would run the counter in raising edge / falling edge mode depending upon the selector setting. The same count is displayed on a set of LCD through the controller.