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plz send me the abstract for wireless switch in efy magazine using op amp and phototransistor?
Normally, appliances are controlled by switches, sensors, etc. However, physical contact with the switches can be dangerous if there is a short circuit. The circuit described here does not require physical contact for the operation of the apparatus. Simply move your hand between the infrared LED (IR LED1) and the phototransistor (T1). The infrared rays transmitted by IR LED1 are detected by the phototransistor to activate the hidden lock, the discharge system, the hand dryer or else. This circuit is very stable and sensitive compared to other CA home appliance control circuits. It's simple, compact and cheap. Current consumption is low in milliamps.


The circuit is built around a CA3140 IC, IRLED1, phototransistor and other discrete components. When 5V is connected to the circuit, the IR LED1 emits infrared rays, which are received by the phototransistor T1 if it is correctly aligned. The collector T1 is connected to the non-inverting pin 3 of IC1. The reversal of the pin 2 of IC1 is connected to the voltage divider preset VR1. Using the VR1 preset can vary the reference voltage on pin 2, which also affects the sensitivity of the phototransistor.

The optical amplifier IC1 amplifies the signal received from the phototransistor. Resistance R3 controls the base current of transistor BC548 (T2). The high output of IC1 on the pin 6 moves the transistor T2 to activate the relay RL1 and switches on the apparatus, eg the hand dryer, through the contacts of the relay. The operation of the circuit is simple. In order to power the device, simply interrupt the infrared rays that fall on the phototransistor through the hand. During the interruption, the appliance remains switched on via the relay. When the hand is removed from the infrared beam, the device switches off via the relay.

[Image: 2A9_oct-_2-efy.jpg]

Mount the circuit to any general purpose PCB. Identify resistors through color coding or using the multimeter. Check polarity and IC pin configuration and mount with base. After soldering the circuit, connect the + 5V supply to the circuit.