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In the same network system, use the same type of cable to minimize the number of contacts in the line. 2. It is not allowed to use a network cable with a wire diameter that is too thin, which will reduce the transmission distance and reduce the equipment that can be connected. If there are many load 485 devices, the wire impedance is not up to the standard, the wire diameter is too thin, the converter quality is poor, the equipment lightning protection is complicated, and the baud rate is increased. When using the RS485 interface, for a specific transmission line, the maximum cable length allowed for data signal transmission from the RS485 interface to the load is inversely proportional to the baud rate of the signal transmission. For instance, consider devices A and B. During a specific timeframe, data transmission is allowed from A to B, and once completed, data transmission from B to A can take place. So take advantage of that and let your systems MCUs implement heart beat handshaking directly though the RS485 communications layer using appropriately designed small packets. In theatre and performance venues, RS-485 networks are used to control lighting and other systems using the DMX512 protocol.

Most engineering companies are accustomed to using Category 5 network cables or over Category 5 network cables as 485 communication lines, which is wrong. RS-485 is a protocol designed to communicate over significant distance with a degree of noise immunity. Composed of (16) UL listed prismatic 3.2V cells in series which have been tested at 7,000 deep discharge cycles to 80% DoD - fully charge and discharge this battery daily for over 15 years without issue. In practice, Cat 5 cables have been used successfully in many installations, but there are some concerns. 1. Ordinary network cables have no shielding layer and cannot prevent common mode interference. Ordinary twisted-pair cables can be used in general occasions, and shielded coaxial cables can be used in environments with relatively high requirements. 1. Ordinary twisted pair shielded cable STP-120Ω (for RS485 & CAN) one pair 20 AWG, the outer diameter of the cable is about 7.7mm. Suitable for indoor, pipeline and general industrial environment. If you need more information on the cable & protocol, refer to the article below. Industrial sites often need to collect multi-point data, analog signals or switch signals. RS-485 adopts half-duplex working mode and supports multi-point data communication.

This length data is mainly affected by signal distortion and noise. Termination resistors also reduce electrical noise sensitivity due to the lower impedance. It should be judged according to the model of the chip in the 485 converter and the model of the 485 device chip, and the load capacity can only be determined according to the chip with a lower index. Generally, there are three levels of 485 chip load capacity-32 units, 128 units and 256 units. All three devices are grounded but there is no indication that the grounds themselves are connected together. 2) Why should it be grounded? 4) Why should the 485 bus adopt the hand-in-hand structure instead of the star structure? This robustness is the main reason why RS-485 is well suited for long-distance networking in noisy environment. The specific transmission distance depends on the surrounding environment. RS485 has no specific physical shape. In theory, the longest transmission distance of RS485 can reach 1200 meters, but the transmission distance in practical applications is shorter than 1200 meters. According to the 485 bus structure theory, under the premise of an ideal environment, the 485 bus transmission distance can reach 1200 meters.

It transmits signals through the voltage difference between the two communication lines, so it is called differential voltage transmission. RS485 transmits binary signals by generating high and low voltages, representing binary 0s and 1s (on and off), enabling efficient long-distance communication in electronically noisy environments. The truth tables of most popular devices, starting with the SN75176, show the output signals inverted. The specifications of the shielded twisted pair used are related to the distance of the 485 communication line and the number of connected devices, as shown in the following table. Rs485 cables not only vary in the structure of the core but also in the number of twisted pairs. It is best to connect a 120Ω terminal resistor at both ends of the RS485 device. The length of the branch line from the bus to each terminal device should be as short as possible, generally not exceeding 5 meters. The RS-485 bus network topology generally adopts a bus-type structure with terminal matching. This wiring method is a bus-type topology. Simply pull a line to the device alone, which can be used to rule out whether the wiring is causing the communication failure. The termination also includes pull up and pull down resistors to establish bias for each data wire for the case when the lines are not being driven by any device.

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