History:
It is impossible to test who invented the first remote control. But the earliest remote controller was invented by an inventor named nikola tesla (1856- 1943) (he used to work for Edison, also known as a genius inventor) in 1898 (U.S. patent number. 6 13809). It is called "method and device for controlling a moving vehicle or a mechanism of a vehicle".
The earliest remote controller used to control TV was Zenith (now acquired by LG), an American electrical appliance company developed in the 1950s. It was wired at the earliest. 1955, the company developed a wireless remote control device named "Flashmatic". But this device can't tell whether the light beam comes from the remote control, and it must be aligned to control it. 1956, robert adler developed a remote controller called "zenith space command", which is also the first modern wireless remote control device. He uses ultrasonic waves to adjust the channel and volume. The frequency of each key is different, but this device may also be interfered by ordinary ultrasonic waves. Some people and animals (such as dogs) can hear the sound from the remote control.
In the1980s, when the semiconductor device for sending and receiving infrared rays was developed, it gradually replaced the ultrasonic control device. Even with the development of other wireless transmission methods (such as Bluetooth), this technology continues to be widely used until now.
Working principle of infrared remote controller:
Many electrical appliances use infrared remote control, so what is the working principle of infrared remote control? First, let's take a look at what is infrared.
The visible light that human eyes can see is arranged from long to short wavelength, which is red, orange, yellow, green, cyan, blue and purple in turn. The wavelength range of red light is 0.62 ~ 0.76 micron; The wavelength range of violet light is 0.38 ~ 0.46 μ m. The light shorter than violet light is called ultraviolet light, and the light longer than red light is called infrared light.
Infrared remote control uses the near infrared ray with the wavelength of 0.76 ~ 1.5μ m to emit control signals. ..
The commonly used infrared remote control system is generally divided into two parts: transmitting and receiving.
The main component of the transmitting part is infrared light emitting diode. It is actually a special kind of light emitting diode. Because its internal material is different from ordinary light-emitting diodes, when a certain voltage is applied across it, it emits infrared rays instead of visible light.
At present, a large number of infrared light-emitting diodes emit infrared light with a wavelength of about 940nm, with the same shape as ordinary 5 light-emitting diodes, but with different colors.
Infrared light-emitting diodes generally have three colors: black, dark blue and transparent.
The method of judging the quality of infrared light-emitting diodes is the same as that of ordinary diodes: measure the positive and negative resistance of infrared light-emitting diodes with a multimeter.
The luminous efficiency of infrared light-emitting diodes can only be accurately measured by special instruments, but it can only be roughly measured by distance method in amateur conditions. The infrared receiving tube of the receiving part is a photosensitive diode.
In practical application, it is necessary to apply reverse bias to the infrared receiving diode to make it work normally, that is, the infrared receiving diode is used in reverse when it is applied in the circuit to obtain higher sensitivity.
Generally, there are two kinds of infrared receiving diodes: round and square.
Because the emission power of infrared light emitting diode is generally small (about 100mW), the signal received by infrared receiving diode is relatively weak, so it is necessary to add high gain amplifier circuit.
In previous years, μPC 1373H, CX20 106A and other special amplifier circuits for infrared reception were commonly used. In recent years, whether amateur production or regular products, most of them use finished infrared receivers.
There are two kinds of packaging for finished infrared receiver: one is metal shield; One is plastic packaging. There are three pins, namely, positive power supply (VDD), negative power supply (GND) and data output (VO or out). Different types of infrared receivers have different pin arrangements. Please refer to the manufacturer's instructions. The advantage of the finished infrared receiver is that it does not need complicated debugging and shell shielding, and it is very convenient to use as a triode. But pay attention to the carrier frequency of the finished infrared receiver when using it.
The common carrier frequency of infrared remote control is 38kHz, which is determined by the 455kHz crystal oscillator used by the transmitter.
At the transmitter, the crystal oscillator is divided by integer, and the frequency division coefficient is generally 12, so 455kHz÷ 12≈37.9 kHz≈38kHz. Some remote control systems use 36kHz, 40kHz and 56kHz, which are generally determined by the oscillation frequency of the crystal oscillator at the transmitter.
The characteristic of infrared remote control is that it does not affect the surrounding environment and interfere with other electrical equipment. Because you can't go through the wall, the household appliances in different rooms can use the universal remote control without interfering with each other; The circuit debugging is simple, as long as the given circuit is connected correctly, it can be put into operation without any debugging; Easy coding and decoding, multi-channel remote control.
Since various manufacturers have produced a large number of infrared remote control ASIC, they can follow the drawings when necessary. Therefore, infrared remote control has been widely used in household appliances and indoor close-range (less than 10 meter) remote control.
Multi-channel control infrared remote control system The multi-channel control infrared emission part generally has many buttons, representing different control functions. When the transmitter presses a key, the receiver has different output states.
The output state of the receiver can be roughly divided into five forms: pulse, level, self-locking, interlocking and data. "Pulse" output means that when the transmitter is pressed, the receiver outputs an "effective pulse" corresponding to the output, and the width is generally around100 ms. "Level" output means that when the transmitter presses the key, the receiver outputs an "effective level" corresponding to the output, and when the transmitter releases the key, the "effective level" at the receiver disappears. The "effective pulse" and "effective level" here may be high or low, depending on the static state of the corresponding output pin. If it is low at static state, "high" is valid; If it is high at rest, the "low level" is valid. In most cases, "high" is effective. "Self-locking" output means that every time the transmitter presses a key, the state of the corresponding output of the receiver changes once, that is, the original high level becomes low level and the original low level becomes high level. This output is suitable for power switch, mute control, etc. This form of output is sometimes called "inversion". "Interlocked" output means that multiple outputs are cleared to each other, and only one output is valid at the same time. This is the case in the selection of TV channels, such as dimming, speed regulation, audio input selection, etc.
"Data" output refers to numbering some transmitting keys, and using several outputs at the receiving end to form a binary number to represent different key inputs.
Generally, in addition to several data outputs, the receiver should also have a "data valid" output to get the data in time later. This output form is generally used to interface with single chip microcomputer or microcomputer. In addition to the above output forms, there are two forms: "latching" and "temporary storage". The so-called "latched" output means that every time the transmitter sends a signal, the receiver will "store" the corresponding output until it receives a new signal; The "scratch" output is similar to the "level" output described above.