“In this Instructable I show you how to make a simple infrared sensor for hobby projects and to learn how an infrared sensor works.
I used an infrared sensor with one of my previous Instructables (the automatic hand sanitizer dispenser) but I didn’t know exactly how this sensor worked so I dived into it a little further.
An IR sensor is basically a device which consists of a pair of an IR LED and a photodiode which are collectively called a photo-coupler or an opto-coupler. The IR LED emits IR radiation. The IR radiation is emitted in a beam from the IR LED. When this beam is disturbed, it widens and “hits” the photodiode. The photodiode converts the IR light into an electrical current. Because the output of the photodiode is not constant, I opted for a circuit with BC547 transistors. I will explain how this works in step 1.
The appendices contain a simple diagram to keep the project clear.
Supplies:
IR LED
Photodiode
Green LED
2 BC547 transistors
100 Ohms resistor
47K resistor
9V Battery
9V Battery connector”