How the remote control works
Every day we often have to use the remote for various tasks. Have you ever wondered how a remote control works? Why doesn't it work to control the AC temperature with your TV remote? Why do you have to point the remote control directly at the TV?
How Infrared Rays Are Used
The first thing you'll notice when you pick up a remote control device is that there are no cables involved. To control a device with a remote, signals are mainly transmitted using electromagnetic waves. Light, X-rays, radio waves, and microwaves—these are all electromagnetic waves.
These waves are essentially pulses of electric and magnetic energy, which travel through air at the speed of light. Most remote controls send signals using infrared rays. Infrared rays are a type of invisible red light. However, some remote controls also work using radio waves or wireless waves.
Looking at the head of the remote-control device, there is a small light-emitting diode made of plastic that emits infrared light. Anything controlled with a remote, such as a TV or video player, will also show a small detector. Usually these devices have a very small infrared light detector on the front. Basically, pressing any button on the remote control sends a beam of infrared radiation towards the TV at the speed of light. And the light detector on the TV picks it up.
Humans cannot detect infrared radiation with the naked eye. So even if you press the button on your remote and look at the LED, you will still see nothing.
Remote Control Code
The remote control doesn't just randomly emit infrared radiation to work. Let's say a remote control device has 20 buttons to control a TV. Now if the remote control emits the same infrared beam for each button, the TV will not recognize each command separately. So each command must also have a separate code. By decoding the codes, the TV can determine what instructions are being given by the remote.
When a button on the remote control is pressed, it emits a series of infrared pulses. Basically each instruction sends a binary coded signal by turning the infrared beam on and off. Note that binary code is a way of communicating any type of information using only zeros and ones (0, 1). Binary code is also used to run computers.
So a short pulse of infrared can send a signal of 1 as a binary code. Again can send 0 signal through pause between pulses. Thus the remote control transmits a code consisting of many zeros and ones with a series of pulses and pauses.
Maybe a code looks like 101101 in binary digits. Which can mean "turn up the volume." Yet another code might be 11110111, which means "turn off the sound."
Along with the commands given to the TV, the remote control also sends a short code. This shortcode identifies the TV you are trying to control. So in case of a particular TV model, only the remote made for that model works.
Because of this short code only the TV can be controlled with the TV remote. Neither the video player nor any other nearby TVs receive signals from that remote. That means, a specific remote-control only works on a specific TV or machine made by a specific company.
But if a common code is used that different TV and video machines can understand, remote controls can be created that will work on multiple machines. This is how the universal remote control works. Any device like TV or video player can be controlled through those remotes. Instead of sending signals specific to just one brand of machine, those remotes can send codes that any model of machine can understand.
Infrared remotes can only control the TV or video player within a short distance. Infrared LEDs are quite small and low power. So its receiver in TV or video player is also small.
Because of this, you usually have to point the remote directly at the machine you are trying to control.
Some remotes have slightly higher performance. Those remotes sometimes bounce infrared rays off walls, mirrors or pictures to change TV channels. Infrared remotes cannot control devices more than a few meters away. Because, infrared rays can easily blend in nature.
A different type of system called radio control is used to control devices over long distances. Radio-controlled cars, trucks, boats, airplanes and robots can be operated using a handheld radio transmitter box.
This control is achieved by sending a signal from an antenna on top of the radio transmitter to a similar antenna on top of the one you want to control. Radio signals can easily travel much farther than infrared radiation. Especially if the transmitters and antennas are large and powerful, specific devices can easily be controlled by radio controlled remotes.