condenser mic and control the appliance at the output through a relay. The input is amplified for better sensitivity and supplied to a counter. This counter is configured to give alternate high and low pulses to the relay which in turn controls the device connected to it.
condenser mic converts the sound signal sensed from the surroundings and converts them into the weak electrical signals and the transistor amplifying circuit amplifies the weak signals. Refer sound amplifier circuit for more details.
to provide pulses to the counter IC 4017. An optocoupler is a 6 pin IC which contains a led, optically coupled to a phototransistor.
The 4017 is a decade counter IC. The output pin Q0 is connected to a red LED. Pin 2, which is the output Q1 is connected to relay as shown in the figure. The appliance is connected between the NC and common pins of the relay. The output Q3, pin 7 is connected to the reset pin 15 of the IC.
Filed Under: Electronic Projects