What is an RS485 connection?
RS-485 is an industrial specification that defines the electrical interface and physical layer for point-to-point communication of electrical devices. The RS-485 standard allows for long cabling distances in electrically noisy environments and can support multiple devices on the same bus.
How many wires are needed for RS485?
RS485 needs 3 conductors and a shield. Many people say it’s a two-wire network but it is not. Two conductors are used to carry the RS485 Differential voltage signal. The Shield is connected to earth/ground at one end only and provides shielding against induced noise.
How far can you run RS485 cable?
4,000 feet
RS485 is popular for inexpensive local networks, multidrop communication links and long haul data transfer over distances of up to 4,000 feet.
Is RS485 the same as Ethernet?
RS-485 can have a “bus” type multi-drop connection (multiple connections to the same cable), while modern Ethernet uses a “hub” type connection. While that sounds like an advantage for RS-485, a “hub and spoke” installation is often a lot easier in practice when you look at where you will run the cables.
Does RS485 provide power?
Most RS-485 transceivers use either a 5-V supply voltage or a 3.3-V supply voltage. Therefore, the internal power dissipation (not due to loading or switching) can be as high as 200 mW (5 V · 40 mA) for some older generation devices.
Does RS485 need ground?
The RS485 interface standard does not specify a ground wire, but such wire is needed to provide a return path for common mode currents and consequently reduce emissions. It may be possible to operate the RS485 loop without a ground wire, but such systems may radiate high levels of EMI.
Does RS485 have polarity?
RS485 polarity labels differ between manufacturers. According to the RS485 standard, the two terminals are, A for negative and B for positive. Most manufacturers will instead use + and –, or some variation such as D+, D . Some manufacturers will label inputs as A and B but get the polarity backward, so A is positive.
Does RS485 need common ground?
RS485 is a differential signal so no common ground is required. Wikipedia says: “Connection of a third wire between the source and receiver may be done to limit the common mode voltage that can be impressed on the receiver inputs.”
Does Rs-485 require ground?
Can I connect RS-485 to Ethernet?
By converting RS485 data signals into Ethernet (TCP or UDP) packets, and vice versa, they enable reliable data transmission to other devices or network server applications. This is accomplished by encapsulating the RS485 data in Ethernet packets in a manner that best fits the type of data being transported.