Why do remote controls use infrared light instead of other wavelengths?


Why do remote controls use infrared light instead of other wavelengths?

In: Technology

Very low wavelength bands are already occupied by radios and microwaves and have a lot of noise.

Visible light is visible of course.

Ultraviolet is too energy intensive to generate, and you definitely don’t want to be shooting x-rays around the living room.

So the near-IR it is.

It is cheap to make and have the advantage that is it line of sight so without adding any complex pair system is it limited to the room and will not control stuff in different room or apartments or even houses that would be the case it you just transmitted for example radio wave.

It had the drawback that it is line of sight so stuff like game consoles uses radio waves. But then you need to pair the device and the remote. That add user complexity and radio is a bit more expensive to use.

You use IR and not visible light so you can’t see the blinking like you can with many digital cameras.

LEDs are the only practical light source for cheap, everyday remote controls. Red and particularly infrared LEDs were available long before other colours.

IR sensors are cheap and easy to manufacturer and do not require approval from the FCC. Since you’ll always be facing the TV, there’s no need for an RF remote, as the IR sensor will always be facing you. Also, since IR is mostly limited to line of sight, it’s highly unlikely that if your neighbor has the same make and model of TV, that their remote will be able to control your TV if they’re very close. Where as with RF, this could be possible, which would make the system more complicated as special encoding methods would be necessary.

IR is cheap and energy-efficient.
Also, the waves attenuate very quickly and can’t penetrate through material, which is actually very beneficial for TVs.
If the waves could over-penetrate, you would have to worry about your neighbor changing your channel. Generally speaking, you’re only going to be using the remote in front of the actual TV, so LOS isn’t an issue.
Not only that, but the lack of interference from other TVs makes it easier to program the remote itself, because you don’t need as many complex ID mechanisms to make sure the right remote is interacting with the right TV.
You can use much more generic signals because of this, which makes everything cheaper and simpler.