Amplifier Timer Circuit Schematic


Posted on Feb 6, 2014

This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared by IC2A & IC2B and monitored by LED D4. When D4 illuminates, albeit for a very short peak, I


Amplifier Timer Circuit Schematic
Click here to download the full size of the above Circuit.

C3 is reset and restarts its counting. Pin 2 of IC3 remains in the low state, the two transistors are on and the relay operates. When, after a 15 minutes delay, no signal appeared at the input, IC3 ends its counting and pin 2 goes high. Q1 & Q2 stop conducting and the relay switches-off. The device is thus completely off as also are the appliances connected to SK1. C5 & R9 reset IC3 at power-on. P2 allows switch-off at any moment.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Zener Oscillator circuits
    Robot eyes
    Remote control by mobile phone
    H-Bridge Motor Driver using MOSFETs and Transistors
    video turret
    circuit transistor tester
    Kapanadze 2
    Astable Flip-flops
    IF processing - video detector circuit
    The basic circuit diagram of a constant current source mirror



    Top