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Because I have not tested all electronic circuits mentioned on this pages, I cannot attest to their accuracy; therefore, I do not provide a warranty of any kind and cannot be held responsible in any manner.

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Infra-Red Proximity Sensors

Using an IR LED as a proximity sensors.

Based on a simple basic Idea, this proximity sensor, is easy to build, easy to calibrate and still, it provides a detection range of 35 cm (range can change depending on the ambient light intensity).

This sensor can be used for most indoor applications where no important ambient light is present. For simplicity, this sensor doesn't provide ambient light immunity, but a more complicated, ambient light ignoring sensor should be discussed in a coming article. However, this sensor can be used to measure the speed of object moving at a very high speed, like in industry or in tachometers. In such applications, ambient light ignoring sensor, which rely on sending 40 Khz pulsed signals cannot be used because there are time gaps between the pulses where the sensor is 'blind'...

Link: IR proximity sensor part I

This article deals with a more advanced IR proximity sensing scheme, as compared to the one proposed in the previous one. It is also more expensive but provides more accurate results even in sunny outdoor environment.

This sensor is practically not affected by ambient light, and it can provide detections ranges that exceed 1 meter. However, The main idea remains the same where Infra-Red light is emitted on an object, which reflects the light back, then the reflected Infra-Red light is sensed with a special IR sensor. The whole difference is in the way IR is sent and received.

Link: IR proximity sensor part II

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