How to distinguish different LED screen boxes?
The display control mode of LED screen is generally divided into two modes: synchronous display and asynchronous display. Usually, the single-chip microcomputer sends instructions to control the light-emitting diode to display the content. The LED screen is actually a dot matrix composed of many diodes. The single-chip microcomputer achieves the purpose of display by switching the diodes.
1. Asynchronous screen (offline screen)
The control microcomputer of the asynchronous LED screen only needs to have an RS232 interface or a USB interface.
A 2-core RVV cord or a Category 5 twisted pair (network cable) is used to connect the display control computer and the LED screen. If the computer RS232 port is used directly, the maximum communication distance is 15 meters (when the baud rate is 19.2K). The communication distance can be extended by reducing the communication baud rate, but generally the maximum distance should not exceed 50 meters.
A control computer can only connect one asynchronous LED screen through the RS232 port. If you need to connect multiple LED screens, either expand multiple RS232 ports, or add an RS485 converter.
Adding an RS485 converter to the RS232 port can extend the communication distance to 1,000 meters.
The asynchronous screen can also use the local area network for display control. Add a RS232/LAN signal transfer device at the control computer, and add a LAN signal/RS232 transfer device at the LED screen, so that the RS232 signal transmission distance can be extended by using the LAN.
In addition, the use of mobile phone short messages, wireless network, GPRS can also realize long-distance display control. However, the disadvantage of wireless transmission is that it cannot guarantee 100% trouble-free signal transmission.
2. Synchronization screen (online screen)
The display control microcomputer of the synchronous LED screen should be equipped with a graphics card with a digital RGB video signal output (DVI) interface.
There should be a spare PCI slot in the control computer, and an LED control signal sending card should be installed.
The digital RGB video signal on the computer graphics card is output to the LED control signal sending card in the computer through the DVI port on the graphics card. The LED control signal sending card converts the signal into a special control signal for the LED screen, and then transmits it to the LED screen through a common network cable. The internal LED control signal picks up the card, and the receiving card distributes the signal to each line of the led display.
The maximum data transmission distance between the display control computer and the LED screen is 100 meters, and the communication line can use a super five twisted pair (network cable). In practical projects, more than one is generally distributed as a backup.
The network cable is a dedicated control signal cable for LEDs and cannot be connected to the switch.
When the control distance exceeds 100 meters, one is to install repeaters, and the other is to use optical fibers.
The disadvantage of adding a repeater to the network cable is that it increases the probability of failure. The disadvantage of using the optical fiber method is that the cost is high: the optical fiber signal access and output equipment should be added at both ends of the control computer and the LED screen.
When the control distance is less than 500 meters, multi-mode fiber can be used; when the control distance is greater than 500 meters, single-mode fiber should be used.
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