Mod-bus ASCII Protocol Connection
How 30 Electric Actuators Share One RS-485 Line (UM1-N-D Example)Many modern electric actuators, such as the UM1-N-D from miT-UniD-cns,
support connecting up to 30 units on a single RS485 network.
This is made possible by RS485 multi-drop communication combined with Modbus protocol.
Instead of wiring each actuator individually, all actuators are connected in a daisy-chain using the same A/B signal wires
( — , the wires between each electric actuator).
Each actuator is assigned a unique Modbus address,
allowing the controller (PLC, DCS, or SCADA) to communicate with them one by one on the same bus.
The controller sends commands—such as open, close, or position setpoint—
to a specific address. Only the addressed actuator responds, while the others remain silent.
This polling method ensures stable and organized communication even with many devices connected.
The result:
- Fewer cables and panels
- Long-distance, noise-resistant communication
- Easy expansion up to ~30 actuators
- Full digital control and feedback (position, status, alarms)
