IR Operated simple Switch

The circuit which I m going to explain and demonstrate today is the one which I have encountered during my Robotics project while I was graduating. This is a very simple Infrared(IR) operated switch which has many numerous of applications. We will first of all talk about the circuit schematic, design and working and then will have a detail discussion on its various applications. We will be using IR Tx Rx pair along with NPN transistor BC547 to demonstrate this circuit.

The IR Transmitter works as a simple LED with a difference that the emitted light coming out from the IR LED falls in IR range of wave spectrum. This is not visible with the naked eyes as the IR rays does not falls in the visible region of the wave spectrum as shown below. But guess yes you can even see the IR rays coming from IR LEDs by viewing it through your Camera, this is very helpful in debugging the faulty IR LEDs.

Wave Spectrum

Next thing we will be using is the IR receiver which detects the IR rays and produces the potential difference across its leads when biased properly. IR receivers are similar to photo diodes. The schematic of our design is as below.

IR Tx Rx PairIR Tx Rx Schematic

I have assembled the components in the above schematic on my breadboard. The leads of the IR transmitter and receivers have been bend in such a way that they face each other neck to neck as shown in the picture below:


This will allow the IR rays from IR transmitter to continuously fall on IR receiver. This makes the IR receiver to conduct and bring the Transistor in ON state and test LED1 remains OFF. As shown below:


When we introduce certain obstacle in the path of the IR rays falling from the IR transmitter to the receiver, the transistor stops conducting and the test LED1 glows indicating that an obstacle have been detected. As shown below:


This circuit finds application in many ways. This can be used to count the objects on a conveyor belt in industries by interfacing the Collector pin of the transistor with a microcontroller. And placing the IR Transmitter module and IR Receiver Module on either side of the conveyor belt and aligning both of them in such a way that the objects while moving on the conveyor belt always cut/obstruct the IR rays. Doing this will produce a pulsating signal on Collector pin of the transistor, by counting this positive edge trigger pulsating signal one can accurately count the no of objects moved on the conveyor belt at a specified time.

However the above mentioned application is just one among many applications which can be implemented in real scenario. Kindly share if you have implementing or have tried other application by commenting on the post below.

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