24 Second Shot Clock

[positive logic]

This is a circuit intended to be used in basketball shot clock.
This is a count-down circuit. To start in 24 seconds; LOAD SW and Reset SW should be push simultaneously. If not, the count will start in 99. 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.

When I do this circuit, the problem that i encounter is the pause/on switch of the counter. When the switch is turn-off and then turn-on the count will not continue from its previous number. It will jump to another number or will end to 00. I never tried to used switch debouncer but I thought it will solve the problem. If you have any idea that will solve the problem just post your comment or any suggestions.

 

[ljcox]

You need both a debounce circuit and one or more 0.1 uF bypass capacitors across the supply.

Strange results will occur otherwise

Len

 

[eeyouth]

Your circuit is working. The only problem is the real time clock. You dont show it in the circuit. I also tried it to circuit maker. The circuit performs well even in breadboard.

Maybe you should make a copyright of your circuit because others will copy it.