Proximity Sensors Made from Infrared

The simple basic idea of building this proximity sensor project is to provide a detection range of 35cm which can be changed depending on the ambient light intensity.

The proximity sensor does not provide ambient light immunity since it is intended to be used for most indoor applications where no ambient light is present. It cannot be used as ambient light ignoring sensor which relies on sending 40kHz pulsed signals because there are times between the pulses where the sensor cannot detect. The sensor can be used to measure the speed of object moving at a very high speed. The solution is to apply a couple of IR LEDs, an op-amp, and resistors.

In the process, the infrared light is sent through IR LEDs then reflected by any object in front of the sensor. Another IR LED is used for detecting the reflected IR light that was emitted from another LED. When a LED is subjected to light, it produces a voltage difference across its leads which is an electrical property. Two designs can be made where one is LOW range, Always ON IR LED and the other is HIGH range, Pulsed IR.

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