Infrared remote control
The IR Remote Control is a remote control device that transmits control signals using near-infrared light with a wavelength between 0.76 and 1.5 μm.
Commonly used infrared remote control systems generally divide and transmit two parts.
(1) The main component of the transmitting portion is an infrared light emitting diode. It is actually a special light-emitting diode. Because its internal material is different from ordinary light-emitting diodes, it emits infrared light instead of visible light when a certain voltage is applied across it.
The widely used infrared light-emitting diode emits infrared light with a wavelength of about 940 nm, and has the same appearance as a normal light-emitting diode, but with different colors.
(2) The main components of the receiving part are infrared receiving diodes, which are generally round and square. In practical applications, the infrared receiving diode should be reverse biased, so that it can work normally, that is, the infrared receiving diode is reversely applied in the circuit, so that high sensitivity can be obtained.
Since the transmitting power of the infrared light emitting diode is generally small (about 100 mW), the signal received by the infrared receiving diode is relatively weak, so it is necessary to increase the high gain amplifying circuit. In recent years, most of the products have adopted the finished infrared receiving head.
There are roughly two types of finished infrared receivers: one with metal shield and one with plastic. There are three pins, power positive (VDD), power negative (GND), and data output (VOUT). The pin arrangement of the infrared receiver is different depending on the model. Refer to the manufacturer's instructions. The advantage of the finished infrared receiver is that it does not require complicated debugging and shielding of the outer casing. It is very convenient to use like a triode. However, pay attention to the carrier frequency of the finished infrared receiver when using.
The commonly used carrier frequency for infrared remote control is 38 kHz, which is determined by the 455 kHz crystal used by the transmitter. At the transmitting end, the crystal is divided by an integer. The division factor is generally 12, so 455 kHz ÷ 12 ≈ 37.9 kHz ≈ 38 kHz. There are also some remote control systems that use 36 kHz, 40 kHz, 56 kHz, etc., which are generally determined by the oscillation frequency of the crystal of the transmitting end.
The feature of infrared remote control is that it does not affect the surrounding environment and does not interfere with other electrical equipment. Because it can't penetrate the wall, the household appliances in different rooms can use the universal remote control without mutual interference; the circuit debugging is simple, as long as the connection is given according to the given circuit, generally no work is required to be put into operation; codec Easy, multi-channel remote control is available. Therefore, infrared remote control has been widely used in home appliances and indoor close-range (less than 10 meters) remote control.
Radio remote control
The RF Remote Control is a remote control device that uses radio signals to control various remote devices. After these signals are received by the remote receiving device, they can command or drive various other mechanical or electronic devices to perform various operations, such as closing the circuit, moving the handle, starting the motor, and then performing the required operations by these machines. As a kind of remote control supplemented with infrared remote control, it has been widely used in garage door, electric door, gate remote control, burglar alarm, industrial control and wireless smart home.
Commonly used radio remote control systems generally divide and transmit two parts.
(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 use mode. The remote control can be used independently as a whole machine, and the external lead wire has a wiring pile head. 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 size, low price, and best use, but the user must Really understand the circuit principle, otherwise it is convenient to use the remote control.
2) The receiving part is generally divided into two types, namely superheterodyne and super regenerative receiving mode, and the super regenerative demodulating circuit is also called a super regenerative detecting circuit, which is actually a regenerative detecting circuit operating in an intermittent oscillation state. . The superheterodyne demodulation circuit is the same as the superheterodyne radio. It sets a local oscillator circuit to generate an oscillating signal, and mixes with the received carrier frequency signal to obtain an intermediate frequency (typically 465 kHz) signal, which is amplified by the intermediate frequency. Detection, demodulation of the data signal. Since the carrier frequency is fixed, its circuit is simpler than the radio. The superheterodyne receiver is stable, sensitive and anti-interference ability; the super regenerative receiver is small and inexpensive.
The carrier frequency commonly used in radio remote control is 315mHz or 433mHz. The remote control uses the open frequency band specified by the state. In this frequency band, if the transmission power is less than 10mW, the coverage is less than 100m or does not exceed the unit range, you do not have to go through the radio. The management committee is free to use for approval. China's open frequency band is 315mHz, while Europe and the United States and other countries are 433mHz, so 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. The rolling code is an upgraded product of fixed code. For those occasions with confidentiality requirements, the rolling code is used.
The difference between IR and RF Remote Control, infrared remote control and wireless remote control are for different carriers. The infrared remote control uses infrared light to transmit control signals. It is characterized by Directional, can not be blocked, the distance is generally no more than 7 meters, free from electromagnetic interference, the TV remote control is the infrared remote control; the radio remote control uses radio waves to transmit control signals, it is characterized by non-directionality, Can not be "face-to-face" control, distance (up to tens of meters, even several kilometers), susceptible to electromagnetic interference. In areas where long-distance penetration or non-directional control is required, such as industrial control, etc., it is easier to solve using a radio remote controller.