Monday Kids Analog Circuit Theory Learning Kits - Use Resistors Capacitors Transistors to Build a Sound Control Logic Circuit

Clap switch kit is composed of a number of resistors, capacitors and transistor amplifier circuit. Circuit is simple, welding easy, inexpensive, and can be widely used in voice-activated switch.

This circuit mainly by the audio amplifier circuit and a flip-flop circuit.

VCC: Connect 5V power supply positive (according to the relay voltage)

1. Characteristics

Operating voltage: 4.5 ~ 5V
PCB size: 28 * 49mm

2. Circuit theory

This circuit is mainly assembled by the audio amplifier circuit and a flip-flop circuit.
Q1 and Q2 form a secondary audio amplifier, an audio signal received from MK1 C1 is coupled to the base of Q1, the amplification is fed directly from the collector to the base of Q2, the collector of Q2 to obtain a negative square wave with to trigger the bistable circuit. R1, C1 limit the frequency response of the circuit for the high sensitivity range of about 1kHz. When the power is turned on, the state of the bistable circuit is off Q4, Q3 saturated, D3 does not shine. When MK1 generates a control signal output after the two-stage amplification of a negative square wave, after the differential processing by the negative spike D1 added to the base of Q3, the circuit rapidly inverted, D3 is illuminated. When MK1 again received control signal, the circuit took place flip, D3 extinguished. The board reserved for external control devices connected to terminals J2, can be a voice for other devices connected via J2 relay. (When connected to both ends of the relay coil relay to be anti and a diode)

This circuit uses a DC 4.5 to 5V power supply, turn off the machine when the LED current of 3 mA, the LED lights up the whole current of 6mA.

4. Component list: