Proximity Detector Circuit

  
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There are 2 ways to build a protximity detector. One is mount the IR LED and the phototransistor so that they face each other. Then the infrared light is detected by the phototransistor. If an object comes between the IR LED and the phototransistor, the light is blocked, and the phototransistor turns off. The other way is to build a proximity dete
Proximity Detector Circuit - schematic

ctor is to mount the IR LED and the IR photodiode next to each other facing the same direction. When an object comes near the IR LED, some infrared light will bounce off the object and be detected by the phototransistor. Although it can`t be seen from the schematic, this circuit assumes that the IR LED and the phototranssitor are oriented so that the phototransistor can detect the infrared light emitted by the IR LED. This can be either indirectly (for a proximity detector) or directly (for an interrupter). Since we are building a proximity detector circuit, they should be oriented so that they are at an angle to each other. This way, when an object or a person (a human body) comes in front of the IR LED and the phototransistor, some of the infrared light will bounce off the person or object and be detected by the phototransistor. Once the phototransistor detects this infrared light, it will conduct electricity and turn on the red LED. You can see how the IR LED and phototransistor should be placed at an angle to each other so that the phototransistor can detect the infrared light if a person or object comes into proximity. If the IR LED and the phototransistor are directly facing each other, the circuit would be an interrupter. The red LED would normally be on. This is because the IR LED would always be beaming infrared light directly on the phototransistor. As a result, the phototransistor would always be conducting...



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