What is a Safety Relay? Principles, Functions, and Wiring Diagram Explained

Compared to standard relays, safety relays are held to higher standards of safety and reliability, adhering to stringent international safety regulations such as IEC 61508 and ISO 13849. Featuring redundancy design, self-diagnostics, and fault detection capabilities, safety relays can operate reliably in complex industrial environments, effectively safeguarding equipment and operators. They are widely used in automated production lines, robotic work cells, and food processing facilities.

✅ Redundancy Design: Multiple independent control circuits ensure that equipment remains in a safe state even if one circuit fails. For example, DADISICK safety relays adopt a dual-channel control coil design, where contact movement only occurs when both coils are either energized or de-energized, effectively preventing false or missed actions.

✅ Fault Detection and Alarm: Safety relays are equipped with built-in self-diagnostic circuits that continuously monitor for faults such as coil short circuits, open circuits, or contact welding. When an anomaly is detected, the relay immediately cuts off the circuit and triggers an alarm signal, ensuring the system remains safe.

This design enables safety relays to provide reliable protection in high-risk scenarios, such as robotic welding and press machine operations.

When abnormal or hazardous conditions occur, operators can press an emergency stop button. The safety relay will immediately actuate, cutting off power or control signals to ensure the equipment stops running and prevents accidents.

2️⃣ Safety Door Monitoring

Safety relays monitor the status of safety doors in equipment that requires internal operation or maintenance. When the door is opened, the relay disconnects the power supply to prevent accidental contact with hazardous components. The equipment can only restart after the safety door is closed and locked.

3️⃣ Two-Hand Control Function

For equipment such as presses or injection molding machines, safety relays enable a two-hand control mechanism. This requires operators to press two buttons simultaneously to start the machine, effectively preventing accidents caused by single-hand misoperation.

4️⃣ Fault Detection and Alarm Function

Safety relays continuously monitor their internal and external circuit states. When a fault is detected, they immediately trigger an alarm via indicators or buzzers and store the fault information for troubleshooting and analysis.