Microchip Technology

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  • Proximity Detector

  • Created: Sep 01, 2014

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A proximity detector is a device that detects the presence of any close-range objects without physical contact. There are different types of proximity sensors, namely, capacitive, inductive, photocell (reflective), magnetic, sonar, radar, ultrasonic sensor, eddy-current, Doppler effect, passive optical, fiber optic sensors, and Hall effect sensors. For the circuit show, it uses a photocell (reflective) type of sensor.

This circuit provides a means of detecting the presence of anything by the reflection of infrared light and provides a direct digital output of object detection. By the use of modulation and high power bursts of infrared at a very low duty cycle, a detection range of over a foot is achieved. It works on the principle of transmitting a beam of modulated infrared light from the emitter diode LED2, and receiving reflections from objects passing in front of the beam with a photodiode detector D1. The circuit consists of an infrared transmitter, photodiode amplifier, and a variable threshold comparator.

Some of the applications for this type of sensor are: parking system, beverage and food can making lines, conveyor systems, roller coasters, and many more. Proximity Detectors can be used for a mechanical switch replacement or to sense human gesturing.

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how many mm (3mm, 5mm) photodiode is used

Posted: Jun 19, 2018



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