Infrared IR Receiver

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The Theory
           The way that this receiver works is very similar to the way that we as humans beings work. We see colors and we act depending on the different things seen. The phototransistors does the same thing, if reacts depending upon the intensity of infrared light being shined at it.

The real difference between the two parallels seen above is that we humans already have a brain to interpret the different wave lenghts of color, where the infrared LED and phototransistor need some 'intelligent' circuitry in order to know what to do when certain data is transmitted.

Sending Data Over IR

           If you're still a little lost as to how information in the form of 0's and 1's can be transmitted using the IR emitter and phototransistor pair, here's a quick circuit you can build that make make things more clear:

Here's how the circuit above works: The 9v battery is hooked up to both the IR Emitter and Phototransistor. The IR Emitter, however, is never turned on unless you press the push button. Since the emitter is not powered on, the phototransistor won't allow current to flow through it, so current will instead flow through the red LED. This means until you press the push button, the red LED remains on. After you press the push button, the emitter shines brightly at the phototransistor and the red LED turns off. Here's a video of this circuit in action:

This should give you a much better visual of how digital 0's and 1's can be transmitted wirelessly using these two infrared components. When the red LED shines, you can see a digital 1. When we press the push button and the red LED turns off, that would be a 0.