A proximity sensor is a device which detects the presence of an object in its proximity. Well the sensor which we are going to make here works well for short distance ranges and is very cheap and easy to build. Photo diode and matching Infrared Led pair will cost you about Rs.12 and all you will need is a resistor and small wires to solder for strength.
A photo diode operates as a normal diode in forward bias and acts as a light sensor in reverse direction. It produces a current proportional to the intensity or amount of light falling on it.
An Infrared led is similar to a normal led except that the former emits out Infrared light instead of visible light. So it works when operated in forward bias condition.
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| Infrared Led |
The output voltage can now be checked with a multimeter. The arrangement of two led's should be in such a way as shown in the figure below (both adjacent to each other). So when an object comes above these the light from infrared led gets reflected from the object and falls on the photo diode. Closer the object, more the amount of reflected light and more the output voltage.
This simple sensor can be used and applied in many exciting ways which we will see in the upcoming posts. So keep making stuff you like and enjoy !!!
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