A wireless remote control, as the name suggests, is a device used to remotely control a machine. It was first developed by Nikola Tesla in the United States in 1898. There are two common types on the market, one is the infrared remote control mode (IR Remote Control) commonly used in home appliances, and the other is the radio remote control mode (RF Remote Control) commonly used in anti-theft alarm equipment, door and window remote control, car remote control, etc.

Whoever invented the first remote control has no idea. But one of the earliest remote controls was developed in 1898 by an inventor named Nikola Tesla (1856-1943) (US Patent No. 613809), called "Method of and Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles."

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　　Infrared Remote Control

　　Infrared remote control (IR Remote Control) is a remote control device that uses near-infrared rays with wavelengths between 0.76 and 1.5 μm to transmit control signals.

　　Commonly used infrared remote control systems are generally divided into two parts: transmitting and receiving.

　　1) The main components of the emission part are infrared light-emitting diodes. It is actually a special light-emitting diode. Because its internal material is different from ordinary light-emitting diodes, when a certain voltage is applied to its two ends, it emits infrared light instead of visible light. The wavelength of infrared light emitted by a large number of infrared light-emitting diodes is about 940nm, and the shape is the same as that of ordinary light-emitting diodes, only the color is different.

　　2) The main components of the receiving part are infrared receiving diodes, which generally have two types: round and square. In practical applications, it is necessary to add reverse bias to the infrared receiving diode, so that it can work normally, that is, when the infrared receiving diode is used in the circuit, it is used in reverse, so that higher sensitivity can be obtained.

　　Since the transmission power of infrared light-emitting diodes is generally small (about 100mW), the signal received by the infrared receiving diode is relatively weak, so a high-gain amplifier circuit should be added. In recent years, most of the infrared receiving heads have been used.

　　There are roughly two kinds of packages for the finished infrared receiver: one is shielded with iron sheet; the other is plastic package. There are three pins, namely power positive (VDD), power negative (GND) and data output (VOUT). The pin arrangement of the infrared receiver is different due to different models, please refer to the manufacturer's instructions for use. The advantage of the finished infrared receiver is that it does not require complicated debugging and shielding of the shell, and it is very convenient to use like a triode. But pay attention to the carrier frequency of the finished infrared receiver when using it.

　　The commonly used carrier frequency of infrared remote control is 38kHz, which is determined by the 455kHz crystal oscillator used by the transmitter. At the transmitting end, the crystal oscillator needs to be divided into integers, and the frequency division coefficient is generally 12, so 455kHz÷12≈37.9kHz≈38kHz. There are also some remote control systems that use 36kHz, 40kHz, 56kHz, etc., which are generally determined by the oscillation frequency of the crystal oscillator at the transmitting end.

　　The characteristic of infrared remote control is that it does not affect the surrounding environment and does not interfere with other electrical equipment. Because it cannot penetrate the wall, household appliances in different rooms can use a universal remote control without mutual interference; circuit debugging is simple, as long as the given circuit is connected correctly, generally it can be put into work without any debugging, easy codec, multi-channel remote control is possible. Therefore, infrared remote control has been widely used in home appliances and indoor short-range (less than 10 meters) remote control.

　　Radio Remote

　　A radio remote control (RF Remote Control) is a remote control device that uses radio signals to control various institutions in the distance. After these signals are received by the remote receiving device, they can instruct or drive various other corresponding mechanical or electronic devices to complete various operations, such as closing the circuit, moving the handle, and starting the motor, and then these machines will perform the required operations. As a kind of remote control that complements the infrared remote control, it has been widely used in the remote control of garage doors, electric doors, gates, burglar alarms, industrial control and wireless smart homes.

　　Commonly used radio remote control systems are generally divided into two parts: transmitting and receiving.

　　1) The transmitting part is generally divided into two types, namely the remote control and the transmitting module. The remote control and the remote control module are for the way of use. The remote control can be used independently as a whole device, and the external lead wires have wiring piles; the remote control module is used as a component in the circuit and is applied according to its pin definition. The advantage of using the remote control module is that it can be seamlessly connected with the application circuit, small in size, low in price, and make the best use of it, but the user must really understand the circuit principle, otherwise it is more convenient to use the remote control.

　　2) The receiving part is generally divided into two types, namely super-heterodyne and super-regenerative receiving methods. The super-regenerative demodulation circuit is also called a super-regenerative detection circuit, which is actually a regenerative detection circuit working in the state of intermittent oscillation. . The super-heterodyne demodulation circuit is the same as the super-heterodyne radio. It is set up with a local oscillator circuit to generate an oscillating signal, and after mixing with the received carrier frequency signal, an intermediate frequency (usually 465kHz) signal is obtained detect and demodulate the data signal. Since the carrier frequency is fixed, its circuit is simpler than that of a radio. The super-heterodyne receiver is stable, has high sensitivity and relatively good anti-interference ability; the super-regenerative receiver is small in size and cost-saving.

　　The commonly used carrier frequency of radio remote control is 315mHz or 433mHz, and the remote control uses the open frequency band specified by the state, in this frequency band, the transmission power is less than 10mW, the coverage is less than 100m or does not exceed the range of the unit, and can be used freely without the approval of the 'Radio Management Committee'. The open frequency band in my country is 315mHz, while in Europe and the United States and other countries it is 433mHz, so the products exported to the above countries should use 433mHz remote control.

　　There are two types of coding methods commonly used in radio remote control, namely fixed code and rolling code. Rolling code is an upgraded product of fixed code. Where there is a confidentiality requirement, rolling coding method is used.

　　The difference between radio remote control and infrared remote control, infrared remote control and wireless remote control is for different carriers, infrared remote control is to use infrared to transmit control signals, it is characterized by directionality, can not be blocked, the distance is generally not more than 7 meters, not subject to electromagnetic interference, TV remote control is infrared remote control; The radio remote control uses radio waves to transmit control signals, which are characterized by non-directionality, can not be 'face-to-face' control, long distance (up to tens of meters, even kilometers), easy to be affected by electromagnetic interference. In areas that require long-distance penetration or non-directional control, such as industrial control, it is easier to use radio remote control.