LED lights are basic components of IR (infrared) remote controls, in fact one of the first applications of light emitting diodes. IR remote controls are part of our daily lives, they are the most common solution for TV, DVD or a HIFI system, where signals do not have to travel long distances. But how does it work, and what exactly does it have to do with LEDs?
IR or infrared light is an electromagnetic radiation invisible to the eye. This is due its wavelength which is longer than visible lights. The basic idea behind the operation of the IR remote is that the control, containing one or two LEDs sends a signal an infrared radiation decoded by the receiver. The components of a remote control are the buttons, an integrated circuit, the button contacts and the LED. Once a button is hit, it touches via its contact a certain part of the circuit which makes the LED release a beam of light (an infrared radiation focused to a beam by a plastic lens). This beam is an encoded data, a sequence of on and off modes, which is decoded by the receiver by converting the infrared radiation to an electric current. Each button has a different code released, which also depends on the make of the device.
One of the main advantages of IR remote controls is their easy and relatively inexpensive application. Their short range is often looked at as a disadvantage (you need to be near the device to be able to operate it), however in most applications, it is not necessary to be any further we are usually in front of the telly anyway when we want to operate it. Another slight disadvantage is that they are directional, so the control needs to be pointed exactly towards the receiver to be able to operate it.
This is due to the low intensity of light the remote control emits, and this can easily be improved if the remote control includes two LEDs for sending signals. That broadens and strengthens the signal, so pointing does not have to be that punctual. IR remotes also need line-of-sight to communicate, so the signals dont go through walls or corners. This can actually be an advantage as well, as separate remotes wont interfere with each other in nearby rooms. Infrared light would actually be easy to interfere, as sunlight, fluorescent bulbs and even the human body emits some infrared light. These are excluded by filters that block lights at other wavelengths than the controllers.
An alternative solution for remote controls is the RF or radio frequency remote control, which uses radio waves instead of light waves to transfer signals. The main advantage of the RF control is that you do not have to be in line-of-sight to operate the application, and it also transmits through walls, which means you can hide the receiver for instance in a cabinet or behind a piece of furniture. Communication also transmits from larger distances than an IR control. On the other hand, this is not the best solution for televisions for instance, which can be found in several rooms of a house. This technical solution is also somewhat more expensive. RF controls are common for garage door openers, gate openers, car-alarm fobs or satellite TV receivers. Bluetooth communication is also a form of transferring data common in cell phones.