But these are signal wires and the network always requires a return path. The ideal RS485 network requires a dedicated wire for ground. The RS485 network is wrongly referred to as a "2 wires plus shield" network. The shielding may be braided (be formed by a mesh of thin conducting wires) or be a foil (consisting of a sheet of metal wound around the conductors): the two types are equivalent. The cabling of the industrial communication systems (Modbus RS485) is different in some ways from the cabling used for power cabling and the electrician may experience some difficulties if he is not an expert in Modbus communication networks. The cabling is done such that all these devices are connected in parallel. Any other way of connecting the devices together is not recommended as it might cause communication issues or damage to the overall system. This works and is sometimes also recommended by many vendors. The shield works as a "drain" for any noise that could be picked up by the RS485 network and "drain" it to ground. The primary occasion for using RS485 cables is to create a network where multiple devices, such as sensors, controllers, or instruments, must communicate over relatively long distances.

No, There may be interference from the high voltages and currents present on the mains wires, and if there is any insulation fault, arcing, etc. on the mains wires, it could put dangerous voltages on the low-voltage RS485 network cable. Ensure SSCOM is added to the firewall, otherwise the firewall may block TCP connections, or test by temporarily disabling all firewalls on the computer. I think RTU units do not reply to ASCII requests and vice-versa, but may this lead to problems? No. Cat 5e-UTP (unshielded twisted pair) which may work over shorter distances in less demanding applications with low EMI noise levels. We've had a few cases where people buy FTDI cables online at a bargain (less than $15) and then it doesn't work. We recommend FTDI cables as they are the best quality. For communications, many of their products are equipped with an RS232 or RS485 serial port. The serial RS232 to RS485 converter and RS232 to RS422 converter units, also called serial converters, are small electronic devices used to convert a serial RS232 signal, (for example the COM port in older computers) into either RS485 or RS422 signals.

For fixed laying Maximum shielding capacity in accordance with EMC requirements, Cable for Modbus bus systems, SUCOnet P, Modulink P, VariNet-P, Dry and damp environments, rs485 cable Suitable for various bus systems based on RS485 / RS422. Some of these converters can convert from RS232 to both RS485 and RS422 however many standard models only has one of the protocols. The devices use modbus RTU except for one that uses modbus ASCII. A Modbus RS485 connects a Master device to one or more Slave devices. And even worse, if you have a non opto-isolated device installed on that network, any noise could "drain" to ground through the device itself instead of flowing through the ground terminal at the end of the line, damaging the device in the process! QUICK TIP- Reversing the ‘A’ and ‘B’ connections of a device can lead to NOT being able to communicate with that device. QUICK TIP- This arrangement improves immunity to electromagnetic disturbances because the cable forms a series of successive coils, each of which faces in the opposite direction to the next one: in this manner any magnetic field in the environment traverses each pair of coils in opposite directions and its effect is thus very reduced (theoretically, the effect on each coil is exactly the opposite of the effect on the next one and thus the effect is cancelled).

Normally, this connection is made at one end of the main cable. No matter the devices, it is always good on real site installation to use a shielded cable, with 18-22AWG wiring and the shield connected ONLY to one end of the line. Here they are listed on the official FTDI site. Your content goes here. The A signals of all devices should be connected with each other and the same goes for the B signals. It gets away most of the time with this configuration, with the shield draining noise and providing the ground reference at the same time. But it does not work ALL the time. If you decide to buy non-FTDI cables, then you have to ensure they work on linux or a Raspberry PI without installation of extra drivers and software. RS485, also known as TIA/EIA-485 is a standard serial communications protocol defining the electrical characteristics of a serial converter, drivers and receivers for use in balanced RS485 digital multipoint systems. Both boards support the Modbus protocol and Laurel’s Custom ASCII protocol, as well as half-duplex or full-duplex RS485 communications. Rs485 is low impedance balanced , so twisting the pair helps with noise immunity as well as reducing the attenuation effect of higher baud rates due to the parallel capacitance of the wires in the cable jacket over the long lengths.