Knowledge Base

RS485 circuits contain 2 wires, A and B. The PC485 has screw terminals for A and B, plus one labelled G (for Gnd). If you are using screened cable (2 cores + shield), connect the shield to G.

With an RS485 hookup all A terminals on all devices should be connected together and all B wires should be connected together. If you should swap A and B somewhere the system will not work. For long runs it pays to use shielded twisted pair cable. In that case the shield should connect to the 0V or Gnd terminal of each RS485 device.

A system may contain up to 32 PC485s or similar devices on one pair of wires.