- Long Delay Timer Circuit: 35 Minute Battery-Powered Design
- Build Your Custom 3-9 Minute Beep Timer Circuit
- Build Your Amplifier Timer Circuit – 15 Minute Delay
- Timed Beeper Circuit: Build Your Precise Timer!
- Build Your 30-Minute Bedside Lamp Timer Circuit
- Time Delay Circuit: Build Your Appliance Protector
- Midnight Security Light Circuit: A 1:00 AM Intrusion Defense
- Delay Relay Circuit: 12V, 15s
- Build a Powerful 1300W Space Heater Circuit Diagram
- Building a 1-Second Delayed Pulse with the 555 Timer
- 555 Timer Mono Stable Circuit Design & Build Guide
- Build Precise Time Delays with a 12-Stage Binary Counter
- Time Delay Circuit: 5A Output from Low Voltage Batteries
- Build a Powerful 1300W AC Heater Circuit Design
- Build Your 9-Second LED Timer & Relay Circuit 9V
Amplifier Timer Circuit Diagram 15 Minute Auto-Off
Deactivate the amplifier when idle for 15 minutes.
Powered by amplifier tape-output
Circuit diagram
Parts:
- R1,R8 1K 1/4W Resistors
- R2,R3 4K7 1/4W Resistors
- R4 22K 1/4W Resistor
- R5 4M7 1/4W Resistor
- R6,R9 10K 1/4W Resistors
- R7 1M5 1/4W Resistor
- R10 100K 1/4W Resistor
- R11 15K 1/4W Resistor
- R12 10M 1/4W Resistor
- R13 1M 1/4W Resistor
- R14 8K2 1/4W Resistor
- R15 1K8 1/4W Resistor
- C1 470µF 25V Electrolytic Capacitor
- C2,C3,C6 100nF 63V Polyester Capacitors
- C4,C5 10µF 25V Electrolytic Capacitors
- D1 Diode bridge 100V 1A
- D2,D7 1N4002 100V 1A Diodes
- D3 Red LED 5mm.
- D4 Yellow LED 5mm.
- D5,D6 1N4148 75V 150mA Diodes
- IC1 78L12 12V 100mA Voltage regulator IC
- IC2 LM358 Low Power Dual Op-amp
- IC3 4060 14 stage ripple counter and oscillator IC
- Q1 BC557 45V 100mA PNP Transistor
- Q2 BC337 45V 800mA NPN Transistor
- J1 RCA audio input socket
- P1 SPST Mains suited Pushbutton
- P2 SPST Pushbutton
- T1 220V Primary, 12V Secondary 3VA Mains transformer
- RL1 10.5V 270 Ohm Relay with SPST 5A 220V switch
- PL1 Male Mains plug
- SK1 Female Mains socket
Circuit operation:
This circuit disables an amplifier or any other device if a low level audio signal absent from its input for at least 15 minutes. Activating P1, the device is energized, supplying power to any device connected to SK1. The audio signal is amplified and squared using IC2’s A and B channels and monitored by LED D4. When D4 is illuminated, though briefly, IC3 is reset and begins its counting sequence again. Pin 2 of IC3 maintains its low state, allowing both transistors to conduct and the relay to operate. After 15 minutes elapse, without a signal at the input, IC3 concludes its counting and pin 2 transitions to a high state. Consequently, transistors Q1 and Q2 cease conduction, and the relay deactivates. The device, therefore, is completely switched off, along with any devices connected to SK1. C5 and R9 reset IC3 upon power-on. P2 allows the device to be switched off at any moment.
Notes:
- Connect either the left or right channel tape output of your amplifier to J1.
- You can use two RCA input sockets wired in parallel to enable audio signal pickup from both stereo channels.
- The delay duration can be adjusted by altering the values of R13 and/or C6.
- If operating a device not supplied by the mains, utilize a double-pole relay switch, connecting the second switch in series with the device’s power supply.
circuit from http://www.redcircuits.com/