As artificial replications of human senses continue to give robots all the capabilities required to come to life. The line separating the two fades. Among all the senses vision is a vital sense in humans. Allowing us to learn more about the surrounding world than we do with any of the other four senses. An infrared sensors (IR sensor) is an electronic device used to sense some aspects of the surroundings and measure the heat of an object as well as detect motion, extending the sense of vision to machines.

If vision is the art of seeing the invisible, then IR sensors take it literally as these sensors use infrared radiations which are invisible to our eyes. This article aims to familiarize you with the working of IR sensors and provide you with some cool project ideas using them.

Principle and working

An IR sensor consists of an IR Receiver and an IR Emitter. IR emitter is an IR LED that continuously emits infrared radiations while power is supplied to it. IR receiver can be thought of as a transistor with its base current determined by the intensity of IR light received. Lower intensity of IR light causes higher resistance between collector-emitter terminals of transistors and limits current from collector to emitter. This change of resistance will further change the voltage at the output of voltage divider. In others words, the greater the intensity of IR light hitting IR receiver, the lower the resistance of IR receiver. Hence the output voltage of voltage divider will decrease.

How does IR receiver detect?

IR detectors are little microchips with a photocell that are tuned to recognize infrared light. Most commonly used for remote control detection. Every TV and DVD player has one of these in the front to listen for the IR signal from the clicker. Inside the remote control is a matching IR LED. It emits IR pulses to tell the TV to turn on, off or change channels. Therefore the underlying working principle of the IR sensor is: photo-diode’s resistance and output voltage change in proportion to the IR light received.

10 IR sensor projects

Gesture control using IR sensors We can recognize three kinds of gestures which are left-right swipe, moving hand forward-backward and waving using two IR sensors. Trigger mechanism is used for this application. Left -right swipe: When we swipe left, we move our hand from right to left. The right-IR sensor detects this movement first and raises a flag. Now only if any movement is detected at the left-IR sensor it recognizes it as a left swipe. Similar for right swipe as well. Waving: we simply count the number of times the person swiped right and left consecutively within a period. Line follower robot These robots detect a black or dark line on a lighter surface. An array of IR sensors is used to calculate reactance of surface beneath them. As black absorbs more light, the black line has lesser reflectance value than lighter surface. This parameter is used to detect the position of the line by the robot. By estimating whether the line underneath them is shifting toward their left or right as they move over them, they give respective signals to the motors to turn left or right to maintain a steady center with respect to the line. Learn how to build one here? Multi touch control The touchscreen uses infrared IR sensors to detect fingers and other objects on the screen. An IR laser at each corner shines IR light across the surface of the screen. When a finger or other object touches the surface, it causes the IR light to scatter in many directions. Some of this light is directed down into the screen, towards an array of 64 IR sensors. By scanning through the sensors, you can determine the x and y position of the touch event(s) and use this to control a variety of apps. Arduino based IR thermometer Infrared thermometer sensor can be used to detect temperature in non-contact method. MLX90614 infrared thermometer from Melexis is a commonly used non-contact temperature sensing device. Wireless Keyboard from TV Remote The basic idea of this project is when you hit a button on your TV remote. By using a IR receiver and an Arduino we can decode it and the decoded values can be utilized to perform different keyboard operations. Learn Arduino here!. Automated room lighting system The aim of this project is to automatically turn on or off the lights in a room by detecting the human movement. Since the job of the circuit is to turn on the light when someone enters the room and turn off the light when the last person leaves the room. So the project must internally count the number of visitors entering and leaving the room. This can be implemented using two IR sensors and a microcontroller. Infrared obstacle avoidance sensor An IR Obstacle Sensor works in accordance with the infrared reflection principle to detect obstacles. When there is no object, the infrared receiver receives no signals. When there is an object ahead which blocks and reflects the infrared light, the infrared receiver will receive signals. Proximity sensors The sensing component in this circuit is IR photo-diode. Higher the amount of InfraRed light falling on the IR photodiode causes more current to flow through it. So bringing the object nearer to the IR LED Photo-Diode pair increases the amount of IR rays from IR LED on the IR photodiode. Therefore voltage at the resistor increases. Eyeball Motion Controlled Wheelchair Using IR Sensors In this project each eye will be having IR transmitter and receiver. Transmitter IR will transmit the light over iris and reflected light will received by IR receiver. Depending upon the intensity of reflected light falling on the receiver, the controller will understand the user intention of wheelchair movement. Now controller will take the decision of moving forward, left or right as long as IR receiver receives the directions information from the user. Precision agriculture using IR sensors on drones Precision agriculture allows farmers to maximize yields using minimal resources such as water, fertilizer, and seeds. By deploying sensors on drones and mapping fields, farmers can begin to understand their crops at a micro scale and conserve resources. Want your own flying drone?

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