How does remote control work?

Remote control dates back to World War II

Few people know that the first remote controls in the world were born to serve the war. Radio frequency remote controls appeared in World War I to guide German naval vessels crashing into Allied boats.

By World War II, the remote control was used to detonate bombs. After the war, their wonderful technology continues to be improved to serve effectively in human life. And so far, it can be said, almost everyone used a remote control to control a certain device.

Initially, remote control was used using RF radio technology (Radio Frequency) and then started using IR (Infrared Remote) infrared technology to the remote control. Currently in life, we use both types of remote controls. So, what is the difference in structure, features and limitations of each type?

Infrared remote control (IR)

Today, this is the kind of remote control that plays a 'dominant role ' in most home appliances. An IR controller will include the basic components in a digital cable junction box as follows: Buttons; an integrated circuit board; contact points; light emitting diodes (LEDs).

The basic principle of this remote control is to use infrared light of the electromagnetic spectrum that the naked eye cannot see to transfer the signal to the joystick device. It acts as a signal generator, which emits infrared light pulses carrying a specific binary code. When we push a button on the outside, we will operate a series of operations that make the joystick device execute the command of that button.

Diagram of remote controller.(Photo: HowStuffWorks)

This procedure is as follows: First, when you click on a button like 'Volume up', for example, it will touch the contact knob below and connect a volume boost circuit on the circuit. Integrated circuits can detect each specific circuit for each button. Next, these circuits will send signals to the front LED. From here, the LED will emit a series of light pulses containing binary codes (including numbers 1 and 0) corresponding to the 'volume up' command. This code includes many sub-codes such as start, volume up, device address code and stop when we release the button.

On the joystick part, it will include an infrared signal receiver located on the front so that it can easily receive signals from the remote control. After confirming that the address code originated correctly from its controller, they would decode the light pulses into binary data so that the device's processor could understand and execute the commands. corresponding.

Currently, we use IR control device for almost all household appliances such as TV, stereo, air conditioner . They are very durable, however, there are limitations related to the nature of transmitting only in a straight line of light. Therefore, the IR controller has a range of only 10 meters and cannot be transmitted through walls or around corners. They only work well when pointing straight or near the receiver position of the joystick.

In addition, infrared light sources are everywhere such as sunlight, fluorescent bulbs, from the human body . so it can cause IR control to be disturbed. To avoid this phenomenon, one must install the filter of the receiver unit to receive specific wavelengths or frequencies of infrared light suitable for it and block the light at another wavelength to limit interference to a maximum extent.

Remote control by radio frequency (RF)

It is the first kind of remote control and still holds an important and popular role in life. If the IR controller is only for indoor use, the RF controller is used for many external items such as garage door openers, signaling systems to see if remote electronic toys even control satellites and laptop and smartphone systems .

Some remote control.(Source: Internet)

With this type of control, it also uses the same principle as infrared control but instead of sending light signals, it transmits radio waves corresponding to binary commands. The radio receiver on the controlled device receives the signal and decodes it. Compared to IR control, its biggest advantage is its wide transmission range, which can be used to control the device to more than 30 meters and can control through walls, glass .

However, it also has limitations that radio signals are also ubiquitous in the space due to the hundreds of machines that use radio signals at different frequencies. Therefore, interference is avoided by transmitting at specific frequencies and by embedding the digital address of the receiving device in radio signals. This helps the radio receiver on the device respond correctly to the signal.

Currently, both types of controls are widely used in life. It is also possible to integrate both to create universal types of remote controls that control many types of devices at the same time or just press a button to automatically execute a sequence of sequential commands. In addition, people improved extensions to convert radio signals into infrared pulses to expand the scope of control of household devices .