Amplifier Timers

Published:2013/7/30 20:45:00 Author:muriel | Keyword: Amplifier Timers | From:SeekIC

Parts:R1,R8 1K 1/4W ResistorsR2,R3 4K7 1/4W ResistorsR4 22K 1/4W ResistorR5 4M7 1/4W ResistorR6,R9 10K 1/4W ResistorsR7 1M5 1/4W ResistorR10 100K 1/4W ResistorR11 15K 1/4W ResistorR12 10M 1/4W ResistorR13 1M 1/4W ResistorR14 8K2 1/4W ResistorR15 1K8 1/4W ResistorC1 470µF 25V Electrolytic CapacitorC2,C3,C6 100nF 63V Polyester CapacitorsC4,C5 10µF 25V Electrolytic CapacitorsD1 Diode bridge 100V 1A D2,D7 1N4002 100V 1A DiodesD3 Red LED 5mm.D4 Yellow LED 5mm.D5,D6 1N4148 75V 150mA DiodesIC1 78L12 12V 100mA Voltage regulator ICIC2 LM358 Low Power Dual Op-ampIC3 4060 14 stage ripple counter and oscillator ICQ1 BC557 45V 100mA PNP TransistorQ2 BC337 45V 800mA NPN TransistorJ1 RCA audio input socketP1 SPST Mains suited PushbuttonP2 SPST PushbuttonT1 220V Primary, 12V Secondary 3VA Mains transformerRL1 10.5V 270 Ohm Relay with SPST 5A 220V switchPL1 Male Mains plugSK1 Female Mains socket Circuit operation: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 IC2 A & B and monitored by LED D4. When D4 illuminates, albeit for a very short peak, IC3 is reset and restarts its counting. Pin 2 of IC3 remains at 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. Notes:Simply connect left or right channel tape output of your amplifier to J1.You can employ two RCA input sockets wired in parallel to allow pick-up audio signals from both stereo channels.The delay time can be varied changing R13 and/or C6 values.Needing to operate a device not supplied by power mains, use a double pole relay switch, connecting the second pole switch in series with the device's supply.



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