Overview

The WEIDMULLER RSSD 800390 is an electromechanical interface relay module that provides signal isolation and power amplification between low-power control systems (e.g., PLCs) and high-power field actuators. It allows a low-voltage, low-current signal to safely switch larger loads while protecting sensitive electronics from surges, transients, and ground loops. Its compact, DIN rail-compatible design supports high-density panel mounting, making it a reliable solution for industrial control cabinets.

Technical Data

Typical Applications

• Solenoid Valve Control: Switch AC solenoids via a safe 24 VDC PLC output while suppressing back EMF.

• Motor Contactor Interfacing: Drive contactor coils or soft-starter circuits with isolation from the control system.

• Signal Isolation for DCS/PLC: Prevent electrical noise from reaching sensitive controllers in SCADA or distributed control systems.

• Pilot Lamps & Indicators: Safely switch AC panel lights, horns, or alarms using low-voltage control signals.

The LED status indicator provides immediate visual feedback for operation and troubleshooting.

FAQ

Q1: What is “Galvanic Isolation” for this relay?
A1: The input (coil) and output (contacts) circuits are electrically separate. Signals are transferred magnetically, protecting the PLC from high voltages or noise on the load side.

Q2: Why is the free-wheeling diode important?
A2: When the coil turns off, the collapsing magnetic field generates a high-voltage spike. The diode safely dissipates this spike, preventing damage to the PLC output transistor.

Q3: What does “1 C/O” mean?
A3: “1 C/O” is a Single Pole Double Throw (SPDT) contact: one common terminal connects to Normally Open (NO) when energized or Normally Closed (NC) when de-energized, providing flexible switching options.