Ten count buzzer
74HC00, 74HC02, 74HC191
How would you like to make a buzzer that sounds only if you press the key 10 times, not 8 times or 12 times. You need to press the key exactly 10 times to make this buzzer sound, and we'll find out why in this project.
This buzzer is a ten count buzzer that counts the number of pulses using the counter IC. You can see by the schematic that the pulses are generated by S1 and U1 "a".
IC2 is a counter that generates an output from "b" after receiving 10 input pulses. S2 is a reset switch for resetting the count to zero. "c" is a circuit that causes the buzzer to sound for the preset time when the output is produced, "d" is an oscillator which generates the buzzer sound. Its output signal is amplified by Q1 and activates the speaker.
Let's see how the project works. Turn power ON and press S2 to reset the counter. Now you can check the buzzer performance. Press S1 10 times. Do you hear a buzzer sound from the speaker?
Be sure to press S2 if you want to use this project again.