At first we must know, What is a proximity sensor?
It is basically a sensor which detects if any object is within some distance or not and gives us alert accordingly. Although it may seem tough,its working principle is not that much hard. So, let us now learn how it works.

Working Principle of Proximity Sensor: (Optional yet Recommended)
There are various types of proximity sensors (like an Ultrasonic distance Sensor can easily be converted into a proximity sensor. Also we can use IR LED and IR Receiver pair or a visible light LED and LDR pair to make proximity sensor etc). Here we shall make Proximity Sensor by using IR LED and IR receiver.

So, how it works?
Basically, an IR LED is used to transmit IR rays and an IR receiver is placed near the LED (obviously not facing the LED). So, when an object is present over the LED, the IR rays are reflected by the obstacle and comes to the IR Receiver. When IR rays struck the IR Receiver (which is basically a Photodiode or a Phototransistor), its resistance decreases significantly in reverse biased mode, which in turn causes a change of voltage in an external resistor. A voltage comparator IC can easily detect this voltage-change and send alert accordingly.

How to build it:

COMPONENTS NEEDED:

1)LM 358 IC(or any other op-amp such as IC 741 etc)(Here,we shall use LM 358 IC)

2)1 IR LED and 1 IR Reciever(Photodiode)

3)Resistors :-

           270  ohm – 2 pieces

           10k ohm – 1  piece

4)Potentiometer (10k or 100k)

5)Power Source (3 – 12 volt)

6)Breadboard

7)Jumper Wires(preferred) or single stranded wire

8)Visible Light LED and a buzzer(optional)

Now as you have gathered all the required materials, make the circuit below in your breadboard strictly following the circuit diagram below.

Circuit Diagram:

Here I am adding Pinout diagram of LM358 IC too.

For those who are working with ICs first time,the pins of an IC are numbered anti-clockwise around the IC(chip) starting near the notch or dot. The diagram shows the numbering for an 8-pin IC, but the principle is same for all ICs.

NOTE:- If you want to improve your sensor’s sensitivity further, you can put three more IR LEDs to cover all four directions of the IR Receiver. You will have to connect the other three LEDs in parallel connection  with the first IR LED.

Also,you can add a buzzer to create a buzzing sound when an obstacle is placed in proximity to the sensor.You will have to add that buzzer in  parallel connection to that visible light LED.

Congrats,you have made your own Proximity Sensor.

COURTESY:  TechieRka

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