1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Audio Perimeter Monitor

Discussion in 'Electronic Projects' started by ElectroMaster, Jul 27, 2002.

Thread Status:
Not open for further replies.
  1. ElectroMaster

    ElectroMaster Administrator

    Joined:
    Jul 5, 2002
    Messages:
    2,059
    Likes:
    127
    Location:
    Broadbeach, AU
    Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area. The cable can be buried in a hosepipe or duct and is concealed out of sight. The mic is an ordinary dynamic mic insert and should be housed in a waterproof enclosure with the rest of the circuit.

    The mic output is amplified by the two transistors, the output is fed down the cable via the 220u capacitor. Here, it has a dual purpose of preventing the DC supply from upsetting the bias of the circuit, and also allowing the smaller ac audio output to pass down the line. At the power supply, the audio is recovered by the 10k preset and 220u capacitor. It is used to feed a small audio amplifier (such as the 2watt design) shown earlier on this site.

    [​IMG]
     
Thread Status:
Not open for further replies.

Share This Page