circuit harness wiring

Showing posts with label timer. Show all posts

Sunday, October 6, 2013

Amplifier Timer Circuit Diagram

Turns-off your amplifier when idle for 15 minutes, Fed by amplifier tape-output

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, IC3 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.

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

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 to the device supply.

Thursday, April 11, 2013

Touch Free Timer Switch

This type of infrared proximity circuit is widely used as an electric switch where physical contact is not desired for hygiene purpose. For example, we commonly see use of infrared proximity sensors on public drinking fountains and in public washrooms. The simple circuit presented here can be operated by moving your hand in front of it. This is achieved by detecting the infrared light reflected by your hand onto a receiver device.

Fig. 1: Touch-Free Timer Switch Circuit diagram :

Touch-Free Timer Switch-Circuit diagram

Fig. 1 shows the circuit of the touch-free timer switch. It has two sections: transmitter and receiver. The IR transmitter is built around timer LMC555 (IC1), which is wired as an astable multivibrator. The multivibrator produces 38kHz pulses (at low duty cycle) that drive an infrared LED (LED1). This frequency can be tuned using a 10-kilo-ohm preset (VR1). A 220-ohm series resistor (R3) ensures that the current consumption of the IR transmitter is not out of arrangement.

The receiver section is built around IR receiver module TSOP1738 (IRX1), timer LMC555 (IC2) and a few discrete components. The TSOP1738 is an integrated miniaturised receiver for infrared remote control systems. Everything required for IR signal processing, including the PIN diode and preamplifier, are assembled on a lead frame and the epoxy package is designed as an IR filter.

When a short IR burst is received by IRX1 (as you wave your hand in front of the switch), the demodulated pulses are fed to the trigger input (pin 2) of the second LMC555 (IC2). This, in turn, triggers the monostable wired around IC2 and its output pin 3 goes high for a period determined by the 2.2-mega-ohm potentiometer and capacitor C5. This turns off the standby indicator (LED1) and transistor T1 conducts to drive the 5V relay (RL1). LED1 enables you to locate the switch in the dark. AC mains supply to the load to be switched-on is routed through the pole and normally-opened contacts of RL1 as shown in the diagram. The circuit works off regulated 5V DC.

Fig. 2: Pin configurations of TSOP1738, IR LED and BC547

Fig. 2 shows the pin configurations of TSOP1738, IR LED1 and transistor BC547. Assemble the circuit on a general-purpose PCB and enclose in a small plastic cabinet. Fit IR LED1 with a reflecting hood at a recessed position on the front panel of the enclosure. The dome-shaped face of the TSOP1738 should stick out from the front panel. Fit the time-control potentiometer (VR2) in an appropriate position. Finally, fit the standby indicator LED1 inside a suitable LED holder such that it slightly protrudes from the front panel. To prevent unwanted reflection of the IR beam, the finished unit should be mounted such that it does not face a nearby wall.

Fig. 3: Suggested enclosure

Using high-precision linear potentiometer VR2 and capacitor C5 (100µF), the time length can be set from nearly 1 second to 120 seconds. Attach a small paper dial on the front panel of the enclosure and mark various positions of the control knob of VR2 as shown in Fig. 3. The accuracy of the timer depends mainly upon the quality (and value) of timing capacitor C5. In practice, most electrolytic capacitors are rated on the basis of minimum guaranteed value and the real value may be higher.

Source : http://www.ecircuitslab.com/2012/08/touch-free-timer-switch-circuit.html