ir sensors

Posted on Feb 5, 2014

The Infrared emitter detector circuit is very useful if you plan to make a line following robot, or a robot with basic object or obstacle detection. Infrared emitter detector pair sensors are fairly easy to implement, although involved some level of testing and calibration to get right. They can be used for obstacle detection, motion detection, tr

ir sensors
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ansmitters, encoders, and color detection (such as for line following). In order to detect a line, we use the principle of reflection of light over different colors. As we all know, a white color object reflects almost all light incident on it while a black colored object absorbs all. Now, by measuring the variation in the intensity of reflected light we can easily determine the presence/absence of line under the sensor. We use an IR LED which will emit Infrared light and it will be reflected by the surface. The detector acts as a variable resistor whose value depends on the intensity of light falling on its surface. The higher the intensity, the lower is the resistance of the detector. The detector and R2 act as a potential divider. When the intensity is high (reflected from white surface), the resistance of detector is low and so the value of the potential is high. Similarly when the intensity is low (reflected from black surface), the resistance of the detector is high and so the potential is low. This potential is compared with a reference potential. The reference can be varied by the potentiometer (pot). Calibration is required. You have to record potentials of the white as well as black surface and then find their ranges. According these potentials ten set the reference so that for white surface output is. high and for white black surface output is low. R3 resistor prevents excessive current to pass through the LED....

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