24 Second Shot Clock

Circuit : Milardo de Guzman - Philippines
Email : Milardo de Guzman

Description:
This is a circuit intended to be used in basketball shot clock. The timer will count down from 24 seconds and lamp and buzzer will be activated at the end of the timing period
24 second shot clock circuit

Notes:
To start in 24 seconds; 24s LOAD SW and Reset SW should be push simultaneously. If not, the count will start in 99. Pulse input can be connected to 555 astable multivibrator but must be calibrated for real time clock. The PAUSE SW must have a Switch Debouncer so that the counter will count normal when counting is paused and then turn-on.

When the count reach 00, the NOR gate will have an output of logic1 that will turn on the two transistor. The buzzer will rung and light will turn on. The two transistors are continuously turn-on not until LOAD SW and Reset SW is push. All have a +5v power supply.