LED light infrared remote control, ultra-thin infrared remote control, intelligent infrared remote control, infrared air conditioning remote control, infrared universal remote control

LED light infrared remote control, ultra-thin infrared remote control, intelligent infrared remote control, infrared air conditioning remote control, infrared universal remote control

Working principle of TV remote control.

The TV remote control is used for 38KHZ times. It numbers different types of buttons in some form, generates modulation waves according to special integrated circuit chips, and sends them according to infrared diodes. After receiving the TV, encode and decode it, and then perform corresponding actions. Infrared differential signals of different signal frequencies correspond to different types of commands, which are realized by quartz crystal. After electrification, the vibration frequency of quartz crystal is very fast and symmetrical, so different types of pulse frequency can be achieved.

Infrared remote control system

TV remote control.jpg

The universal infrared emission system is composed of two parts: sending and receiving, and is controlled and operated by the special integrated circuit chip for numbering/encoding and decoding. The transmission part includes the key disk matrix, number modulation, and LED infrared transmission includes optical and electrical conversion power amplification circuit, demodulation, encoding and decoding circuit.

TV remote control transmitter and number

There are many special chips for the transmitter of TV remote control, which can be divided into two categories according to the coding method. Next, we will illustrate the category that is very widely used and relatively easy to encode and decode. Now we will take the transmission circuit composed of uPD6121G of NEC in Japan as an example to illustrate the numbering principle. After pressing the transmitter button, the remote control code will be sent out, and the buttons with different remote control codes are also different. The remote control code has the following characteristics:

Pulse width is 0.565ms, interval is 0.56ms, and period is 1.125ms binary combination "0"; Binary combination "1" with pulse width of 0.565ms, interval of 1.685ms and period of 2.25ms.

The above "0" and "1" 32-bit binary codes consist of 38 kHz. In order to improve transmission efficiency and reduce power consumption, secondary modulation is carried out. Then send infrared through the infrared diode.

After pressing the button, the remote control will send the same 32-bit binary code periodically, with a cycle of about 108ms. The duration of a group of code itself and the binary contain "0" and "1" between about 45 and 63 ms.

When a key is pressed for more than 36ms, the crystal oscillator activates the chip and sends a set of 108ms numbered pulses. The 1088ms start code sends the code (9) ms), the result code (4). 5ms), the low 8-bit address code (9) ms~18ms), the high 8-bit address code (9) ms~18ms), the 8-bit data code (9 ms~18ms) reverse code and the 8-bit data (ms~18ms) reverse code. If you press 108 and above for 108 ms, the next transmitted code (burst code) will only consist of at least (9) start ms and end code (2.5 ms).

Code format (the receiving code shall prevail, and the receiving code is opposite to the sending code)

① Bit definition

② Single-issue code format

③ Consecutive code format

Note: Code width algorithm:

Minimum width of 16-bit address code:. 12 × 16=18ms16 bit address code maximum width: 20.24ms × 16=36ms

The width and invariability of 8-bit data code and 8-bit inverse code are known: (1). 12ms+2.24ms) × 8=27ms

⏵ The width of the 32-bit code is (182 bit code) ms+27ms)~(36ms+27ms)

Sanyo TV remote control.jpg

1. The key to how to identify the encoding and decoding is to encode and decode "0" and "1". We can find that when the bit definition "0" and "1" start at a low frequency of 0.56ms, the difference is that the width of the pull-up resistance is different, "0" is 0.56ms, and "1" is 1.68ms. Therefore, we should distinguish "0" and "1" according to the width of the pull-up resistance. If the delay starts after the low power frequency of 0.56ms, in the future of 0.56ms, if the reading level is low, it means that the position is "0", otherwise it is "1". For the sake of reliability, the delay must be a little longer than 0. 56ms, but not more than 1.12ms. Otherwise, if these positions are "0", the next pull-up resistance is read, so (1.12ms+0.56ms)/2=0.84ms is the most valuable, generally about 0.84ms.

2. According to the file format of the code, wait for the start code of 9ms and the result code before reading the code of 4.5ms.

Receiver and codec

The integrated infrared receiver is a kind of infrared reception from infrared emission to output and amplification. It does not need any external component TTL to work with the level signal compatible with the level signal. It is mainly applicable to infrared emission and infrared transmission data.