Amplifier timer / Mohd Hanafi Zaidin and Azrel Assuad Arbai

Zaidin, Mohd Hanafi and Arbai, Azrel Assuad (2003) Amplifier timer / Mohd Hanafi Zaidin and Azrel Assuad Arbai. [Student Project] (Unpublished)


This circuit turn-off an amplifier or any other device when a low level audio fed to its input is absent for 15 minutes at least.
Pushing PI the device is the switched-on feeding any appliance connected to SKI. Input audio signal is boosted and squared by IC2 A & B and monitored by LED D4. when D4 illuminates, albeit for very short peak, IC3 is reset and the restarts its counting. Pin 2 of IC3 remains at the low state, the to transistor are on and the relay operates. When, after the 15 minutes delay, no signal appeared at the input, IC3 end 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 SKI, C5 & R9 reset IC3 at the power on. P2 allows switch-off at any moment.


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