IR detectors are little microchips with a photocell that are tuned to listen to infrared light. They are almost always used for remote control detection – every TV and DVD player has one of these in the front to listen for the IR signal from the clicker. Inside the remote control is a matching IR LED, which emits IR pulses to tell the TV to turn on, off or change channels. IR light is not visible to the human eye, which means it takes a little more work to test a setup.
IR detectors are specially filtered for Infrared light, they are not good at detecting visible light. On the other hand, photocells are good at detecting yellow/green visible light, not good at IR light
IR detectors have a demodulator inside that looks for modulated IR at 38 KHz. Just shining an IR LED wont be detected, it has to be PWM blinking at 38KHz. Photocells do not have any sort of demodulator and can detect any frequency (including DC) within the response speed of the photocell (which is about 1KHz)
IR detectors are digital out – either they detect 38KHz IR signal and output low (0V) or they do not detect any and output high (5V). Photocells act like resistors, the resistance changes depending on how much light they are exposed to
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Thank you for posting this! I’ve been trying to do something like this to make a remote A/C starter (Arduino + Ethernet Shield + IR LED to my window A/C’s IR sensor). Now that summer’s over, though, I’ll have to bookmark this for next year.
When I was trying to make mine, I was trying to use the Arduino function pulseIn() to get the IR codes, but looking at the code, I see that you didn’t use that. Is it not appropriate for this type of application?
As always, somebody posts a great tutorial right after i finish my project. This is fantastic info all in one place.
Since you use delay to set timings, you will find if you build a device that has interrupts, etc, the timings will get off and the tx won’t work. The library in this guys blog is awesome.