Lab number five.
op-amp sound activated switch
components:
1) B1: 9 volt battery
2) R1: 100 ohm resistor
3) R2: 100 k ohm potentiometer
4) R3: 470 ohm resistor
5) R4: 3k resistor
6) R5: 100 ohm resistor
7) C1: 0.1 uF capacitor
8) LED1: light emitting diode
9) T1: 2n3904, NPN transistor
10) Mic1: Electret Microphone
11) IC1a:LM393n op-amp
notes:
1) R2 and R3 create a voltage divider as a reference voltage for the op-amp to compare to the mic. The microphone has a low positive charge with no sound, and a spike of higher voltage when receiving sound. Using R3 we set the reference voltage just below the microphone's base charge.