My Note taking for IR receivers and IR photoresistors using arduino or nodemcu platforms.
Currently, I'm using the following IR photoresistor (also called an IR diode?), mostly by accident because I thought it was an IR receiver. I didn't think there would be a difference between the three pin infrared receiver and the two pin infrared receiver. Oops.
http://www.gikfun.com/leds-c-6_51/5mm-940nm-leds-infrared-emitter-and-ir-receiver-diode-p-519.html
https://forum.arduino.cc/t/cant-get-an-ir-photoresistor-to-work/698649/1
These are very basic components geared towards proximity testing.
These simple two pin emitters and receivers are designed to trigger if something is physically blocking the receiver from receiving the light emitted by the emitter. by an object them from receiving the signal. I imagine people buy them to fix their garage door openers, but you could also use them to detect if a drawer is shut. It is an alternate to a magnet or ultrasonic, depending on your needs I suppose.
I watched the following:
Caleb Rowe - he gives the simple wiring diagram and a perfect description of how to setup the sensor on an Arduino. He also mentions why you might choose a 10k resistor versus another type for those of us who are unfamiliar with electronics. https://www.youtube.com/watch?v=_mOF1JXo1DU
Andres Spiess - I don't think there was a wiring diagram here, but he gives a solid explanation of how the low level IR photoresistor is used in common remote controls to produce a valid signal. You can use the simple two pin emitters for such things, but it will come with some limitations. I believe, but haven't confirmed that three pin IR receivers designed for use with remote controls are designed not to be directional. https://www.youtube.com/watch?v=gADIb1Xw8PE
I'm still watching the following:
Gaven MacDonald - https://www.youtube.com/watch?v=zx4OUXk0LSQ