How IR sensor works


Did you know you can catch a thief using an IR sensor? But wait, what’s IR sensor?

What is IR sensor?

IR stands for Infrared rays. These rays are the source of energy in the form of light invisible to human eyes. IR rays are a type of electromagnetic radiation and their wavelength lies between 700 nm to 100,000 nm.

Infrared sensor or IR sensor is an electronic circuit that works on the principle of Infrared light emission and reflection to detect an object, distance and motion.

Let’s do an experiment.

Things you need:

You will need the following of the Havi Elements.

  • Power Element
  • IR Element
  • Buzzer Element

Accessories required

  • Power bank with USB cable

Prepare the circuit as shown here.

Did you know: Infrared was discovered by Sir William Herschel in 1798.

The experiment

STEP 1: Connect the Power element, IR element, and buzzer element. (IR element has a transmitter, receiver, and control portion, combined together it makes IR sensor)

STEP 2: Tune potentiometer of IR element(which is basically infrared sensor) so the mark on the nob remains in the center.

STEP 3: Switch on the power element. As soon as the energy reaches the IR element, it will release the infrared rays.

STEP 4: Place an object in the path of infrared rays and the buzzer will start making the sound.

Why does it happen?

Working principle of an IR sensor

infrared led working principle
The IR sensor has two types of LEDs. The transparent one is the infrared transmitter and the black LED is the infrared receiver. The transmitter sends infrared light. When infrared light strikes the object it gets blocked and hence is reflected back. The reflected lights are received by the receiver. The receiver senses the rays coming back and that gets noticed by the control portion of the IR element.

infrared light reflection working principle
The IR then lets a “YES” signal pass. The buzzer listens to that YES and follows it as a command to make the “noise”. Interesting, no?

What objects can IR sensor detect?

Any object that reflects the light will activate the IR sensor and make it pass the “YES” signal. But what about the transparent objects like

  1. Glass
  2. Water
  3. Plastic
  4. Colored water

All these objects may or may not reflect the IR light. Actually, it depends on the quality or say transparency of the objects.

Say a glass, if very pure and let’s pass all of the IR light, will not get detected by the IR signals. Try various transparent, semi-transparent and non-transparent glasses around you.

You can try pouring some water in front of the IR element, like creating an artificial waterfall, and see how IR sensor reacts.

Can only an IR transmitter send the IR light?

To answer that, check your element circuit into the sunlight without blocking the way of the IR LED. What happens? The buzzer will make the sound. That means it has received the “YES” from IR even though you didn’t block it?

So from where the receiver has received the IR light? Huh?

Sun – The source of infrared rays

This sun. The sun radiates IR light and is the biggest source of energy for us.
The same is true for fire and high-intensity bulbs and lights. They do emit IR light which the IR receiver detects and passes the “YES” even though there is no object to block the way.

Even your TV and AC remote controls also use IR light. Try to point the remote control against the IR LED and press the buttons, it should send a “YES” signal and buzzer will make the sound.

Why don’t we do all these experiments? We have prepared an experiment observation sheet for you. Download this worksheet and fill the details with what you observe.

Infrared sensor observation worksheet
But How can we catch the thief using IR sensor?

Still, need to explain this? You smart heroes!

Place the IR near to the door or locker in a way so a body part blocks the IR light flow… and…. Dhen…ten….nen…….

Pro tip: You can toggle the IR sensor output using Flip element and with that you can make a theft prevention system too!

Uses of infrared sensor

Infrared is used in diverse sectors in ample ways. The primary uses include tracking, surveillance, night vision, and target location. IR sensor is widely used in the Civil, military, space, and medical domains.

And with this, now it’s your time to create amazing IR sensor projects and helpful inventions.

Check: 13 IR sensor based STEAM projects

Heroes you go!


Liked this article? Share with your friends

Havi Camp

[time_change], 6 PM IST, on zoom call.

A class of Technology and future skills for age 5 to 15.

Get an invite

Error: Contact form not found.

Your Cart
Your cart is empty
Calculate Shipping
Apply Coupon