Sound controlled flip-flop/ Farah Syahida Mohd. Kamal and Noor Shazana Idris

Sound controlled flip-flop can be use such as remote switching on, activating a camera, tape recorder, burglar alarm, etc. The purpose for this project is to identify that when the microphone pick up the sound, it will directly switch on the LED and the buzzer. IC LM324 offers a good gain to enable sound pick up upto 4 metres. It is because the two-stages amplifier built around a quad op-amp IC. The third op-amp is configured as a level detector whose noninverting terminal is fed with the amplified and the filtered signal available at the output of second op-amp. The inverting input of the third op-amp is given a reference voltage from a potential divider consisting of a 10k resistor and 4.7k preset. By adjusting the preset, we can control the sensitivity of the circuit. The sensitivity control helps in rejecting any unwanted sounds. The lOOmF capacitor also helps in bypassing noise. The output of the level detector is square pulses. The circuit operates at 4.5V, so it can easily incorporate in digital circuit. Transistor T! & T2 will switch on when Q output is logic 1. While T2 & T2 conduct when Q output is logic o. Current through the LED & buzzer will changes it direction when the flip-flop is toggles.