Remote control (transmitting) components:
The circuit of the home remote controller mainly includes: 455K crystal oscillator, coding ic, amplifier transistor, emitter tube and other major electronic components, which are driven by two 3V batteries; However, some remote controllers used by international manufacturers have included crystal oscillators and amplifying triodes in their coding IC, which makes the circuit design more convenient and only needs 1 battery drive, which is more environmentally friendly.
Infrared receiving part:
The internal structure of infrared receiver is shown in the above figure, which is mainly composed of photodiode and infrared receiver IC. Its working principle is: photodiode (commonly known as receiving tube).
After receiving the optical signal sent by the infrared emitting tube, it is converted into an electrical signal (micro-ampere current), which is input into the receiving IC, amplified, gained, filtered, demodulated and reshaped, and restored to the original code given by the remote controller, and then input to the code recognition circuit at the back through the signal output pin of the receiving head.
Reasons for using 38khz:
Why use 38KHZ is because it can improve the anti-interference ability of infrared rays and avoid infrared interference in the atmosphere. The principle is as follows: the modulation carrier frequency is generally between 30 kHz 30k Hz-60 khz, and the square wave with duty ratio of 1/3 is mostly used by the transmitter.
455kHz crystal oscillator. At the transmitter, the crystal oscillator should be divided by integer, and the frequency division coefficient is generally 12,455khz ÷12 ≈ 37.9khz ≈ 38khz.
Extended data:
Infrared ray belongs to an electromagnetic ray, and its characteristics are equivalent to radio or X-ray. The light wave visible to human eyes is 380nm-780nm, and the long ray with emission wavelength of 780nm- 1mm is called infrared ray. Although this ray is invisible to naked eyes, infrared signals can be sent and received by infrared transceiver to realize infrared communication.
Using infrared communication, you don't need to connect wires, you only need to aim at the infrared devices of two devices to transmit data. Infrared communication has strong directivity and is suitable for short-distance wireless transmission. The circuit of infrared remote controller is mainly composed of integrated emission chip, crystal oscillator, infrared emission tube, push transistor and conductive rubber.
Infrared emission applications:
1, industrial grade: it can be used for instruments and equipment, medical care instruments, military, anti-counterfeiting and security, stage lighting, tools, USB flash drives, mobile phones, projection teaching flip pens, temperature measuring (ranging) instruments, level meters, marking instruments, level meters, indoor and outdoor decorations and other products;
2. Industrial grade: it can be used for beauty instruments, health care instruments, gifts, consumer products and industrial substitute products;
3, toy level: can be used for flashlights, gyroscopes, consumer gifts, gifts, toys and other products.