Q$.4(15\text{'})$ You are provided with a currency counting machine. People feed bank notes into the slot. An optical sensor $($LED$-$phototransistor pair$)$ is placed to detect when the notes pass through the slot. Each time the note passes by the sensor$,$ the $7414$ Schmitt trigger inverter provides a single pulse to a counting circuit. The output of the sensor is high when its beam is interrupted; otherwise, it is low.

Design a counting circuit to measure and display the number of notes passing through the slot satisfying the following requirements:

Display the count value on $7-$segment LED displays with maximum number of $99($suppose we use decade counter$)$; and the counter value can be cleared either when there is an over flow or manually.

Solution: