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

    Battery-capacity-tester
    Wide-range-peak-detector
    low noise receive aerial
    Supply Voltage Indicator
    doubler voltage with ne555 schematic
    Three transistor audio amplifier
    Analog Filters for Data Conversion
    analog to digital converter pic
    12V-220V Modified Sine-wave Inverter Circuit



    Top