điều khiển từ xa

điều khiển từ xa

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Bạn hỏi remote control trong automation hay cho các thiết bị điện tử (infrared remote control)?
Nếu là remote control cho thiết bị điện tử, tôi chỉ có thể post cho bạn 1 bài viết ngắn
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Infra Red Remote Controls - How They Work
All Infra Red (IR) remote controls use some kind of IR signal. The remotes transmit pulses of IR light to send the signal to the receiver. These IR LEDs transmit light in the frequency range of 30 kHz to 40 kHz. These high frequencies were chosen so that other light sources would not interfere with the receivers ability to correctly receive the transmitted signals. These signals are transmitted by the IR LED in some type of binary code. It turns out that for most consumer electronics this coding is the same. The binary signal varies in length for both time and bit length.
There are really only three different ways that manufacturers choose to code these signals. This coding is usually based on varying the length of pulses, varying the length of spaces between pulses or altering the order between spaces or pulses.
1) Pulse-Width-Coded Signals vary the length of pulses to code the information. In this case if the pulse width is short (approximately 550us) it corresponds to a logical zero or a low. If the pulse width is long (approximately 2200us) it corresponds to a logical one or a high.


2) Space-Coded Signals vary the length of the spaces between pulses to code the information. In this case if the space width is short (approximately 550us) it corresponds to a logical zero or a low. If the space width is long (approximately 1650us) it corresponds to a logical one or a high.


3)Shift-Coded Signals vary the order of pulse space to code the information. In this case if the space width is short (approximately 550us) and the pulse width is long (approximately 1100us) the signal corresponds to a logical one or a high. If the space is long and the pulse is short the signal corresponds to a logical zero or a low.

This coding holds information such as the address to the machine that is using the remote and the command that the machine must follow. The address is very important because without it the signal would be processed by another IR receiver in the area.
When a button on a remote is pushed it sends a string of signals. The first piece of information in the string is called the Header. The Header usually contains a burst of highs that alerts all the IR receivers in the area to the string of data being sent. Following the burst of highs is the address to the specific machine to receive the next piece of data, the command. As long as the button is held down (depressed) the command will continue to repeat over and over. When the button is released a string of code called the stop is transmitted. As you may have guessed it the stop tells the machine to stop its executing the command.
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Được ctech sửa chữa / chuyển vào 14:48 ngày 11/07/2004