Acoustic Sensor

Posted on Feb 5, 2014

This acoustic sensor was originally developed for an industrial application (monitoring a siren), but will also find many domestic applications. Note that the sensor is designed with safety of operation as the top priority: this means that if it fails then in the worst-case scenario it will not itself generate a false indication that a sound is de

Acoustic Sensor
Click here to download the full size of the above Circuit.

tected. Also, the sensor connections are protected against polarity reversal and short-circuits. The supply voltage of 24 V is suitable for industrial use, and the output of the sensor swings over the supply voltage range. The circuit consists of an electret microphone, an amplifier, attenuator, rectifier and a switching stage. MIC1 is supplied with a current of 1 mA by R9. T1 amplifies the signal, decoupled from the supply by C1, to about 1 Vpp. R7 sets the collector current of T1 to a maximum of 0. 5 mA. The operating point is set by feedback resistor R8. The sensitivity of the circuit can be adjusted using potentiometer P1 so that it does not respond to ambient noise levels. Diodes D1 and D2 recitfy the signal and C4 provides smoothing. As soon as the voltage across C4 rises above 0. 5 V, T2 turns on and the LED connected to the collector of the transistor lights. T3 inverts this signal. If the microphone receives no sound, T3 turns on and the output will be at ground. If a signal is detected, T3 turns off and the output is pulled to +24 V by R4 and R5. In order to allow for an output current of 10 mA, T3`s collector resistor needs to be 2. 4 k. If 0. 25 W resistors are to be used, then to be on the safe side this should be made up of two 4. 7 k resistors wired in parallel. Diode D4 protects the circuit from reverse polarity connection, and D3 protects the output from damage if it is inadvertently connected to the supply.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    DC Supply
    200 watt Audio amplifier with STK4050
    800 To 1000Mhz Scanner Converter Circuit
    Telephone Ringer Circuit
    Door Lock Wiring
    200W MOSFET Power Amplifier Schematic Diagram
    shortwave radio receiver circuit project
    Transmit Infrared Signals Through Walls
    2002 Chevy Cavalier heater/AC temp control wont light up at nite
    CD47 (Rodan) Nixie Tube Clock
    AD594 to 597 basic application circuit b
    5W Valve RF Transmitter circuit