Infrared transmitter-receiver principle
Remote control (transmitter) part:
Domestic remote control circuit mainly has: 455K crystal, coding IC, amplified transistor, transmitting tube and so on the main electronic components, 2 3V battery drive; but some of the international manufacturers of the remote control, the coding IC within the crystal and the amplified transistor have been included in the circuit design, more convenient and only need 1 battery drive. More convenient, and only need 1 battery drive, more environmentally friendly.
Infrared receiving part:
Infrared receiving head internal structure as shown above, which is mainly composed of photodiode + infrared receiving IC, the principle of operation: photodiode (commonly known as the receiver tube)
It receives the infrared transmitter tube emits light signals converted to electrical signals (for the microampere current), the electrical signal is input to the receiver IC internal amplification - gain - filtering - amplification - gain - filtering - amplifier. This electrical signal is input to the receiver IC after amplification - gain - filtering - demodulation - shaping and restoration to restore the original code given by the remote control, which is input to the code recognition circuit at the back through the signal output pin of the receiver head.
Reason for using 38khz:
Why 38KHZ is used is because it can improve the anti-interference ability of infrared rays and avoid infrared interference in the atmosphere. The principle is as follows modulating carrier frequency is generally between 30khz and 60khz, most of the use of 38kHz, duty cycle 1/3 of the square wave used by the transmitter.
455kHz crystal decided. In the transmitter side to the crystal to be integer frequency division, frequency division coefficient is generally taken 12, 455kHz ÷ 12 ≈ 37.9kHz ≈ 38kHz.
Expanded information:
Infrared light belongs to a class of electromagnetic rays whose properties are equivalent to those of radio or X-rays. The light waves visible to the human eye are 380nm-780nm, and the long rays emitting wavelengths of 780nm-1mm are called infrared rays. Although the naked eye can not see this light, but the use of infrared transmitting and receiving devices can send and receive infrared signals, the implementation of infrared communication.
Infrared communication requires no wires, and data can be transmitted by aligning the infrared devices of the two devices. Infrared communication is highly directional and is suitable for wireless transmission in close proximity. Infrared remote control circuit mainly consists of: integrated transmitter chip, crystal oscillator, infrared transmitter tube, push crystal transistor, conductive rubber and other components.
Infrared transmitter applications:
1, industrial grade: can be used for instrumentation, health care instruments, military, counterfeit security, stage lighting, tools, USB flash drives, cell phones, projection teaching page turner, temperature measurement (distance) meter, sweeping instrument, line marker, level, indoor and outdoor decoration and other products;
2, sub-industrial grade: can be used for beauty instruments, health care instruments, gift class
3, toy grade: can be used in flashlights, gyroscopes, consumer giveaways, gifts, toys and other products.