Connecting Safety to Robot or PLC

The safety output from the Spin Bridge must be connected to a safety input of the robot or PLC (e.g., emergency stop or safeguard stop circuit).

The Spin Bridge provides safety output as OSSD signals. These signals are designed to initiate a safe stop of the robot when the tool safety system is triggered. The OSSD signals are dual-channel safety outputs designed for Category 3 / Performance Level d (PL d) safety systems.

Safety Signal Overview

The safety system operates as follows:

  • The tool detects unexpected contact (safety sensor)

  • The Spin Bridge outputs a safety signal (OSSD)

  • The robot or PLC must initiate a safe stop

Note

The connected system must be able to receive and react to OSSD safety signals.

The safety system is illustrated in the figure below.

It shows how the safety signal is transmitted from the tool, through the Spin Bridge, to the robot controller, and how the power supply is provided from the robot to the safety system.

The tool detects contact and triggers the Spin Bridge, which sends the OSSD signals Sa and Sb to the robot; the robot stops, and supplies the Spin Bridge with 24 V and 0 V

Safety signal flow from tool to robot controller.

The tool detects contact and triggers the safety system. The Spin Bridge transmits dual-channel OSSD signals (S_a and S_b) to the connected controller, which must initiate a safe stop.

The robot controller provides 24 V and 0 V supply to the Spin Bridge.

Both OSSD channels (S_a and S_b) must be active (high) to allow robot operation. The dual-channel design provides redundancy and fault detection: if either channel is interrupted or goes low, the controller must perform a safe stop.

Warning

If the safety cable is not correctly connected, the safety function will not operate. The system must NOT be used in collaborative applications without a functioning safety connection.

Electrical Requirements

The Spin Bridge and the robot or PLC must share the same electrical reference: 24 V and 0 V from the safety cable must be connected, and the safety input circuit must use the same voltage potential. The shared reference is required for both safety signal integrity and I/O communication.

Warning

If 24 V and 0 V are not shared, safety signals may not be detected, the system may behave unpredictably, and the safety function may fail. Connect 24 V and 0 V from the safety cable to the robot or PLC.

Connection Principles

Two typical connection methods are used:

1. Direct OSSD connection (recommended)

  • Connect OSSD outputs from Spin Bridge directly to robot/PLC safety inputs

  • Requires support for OSSD signals

2. Safety relay (if OSSD not supported)

  • Use a safety relay to convert OSSD signals

  • Relay output connects to robot/PLC E-stop circuit

Note

Always verify compatibility with your robot or PLC safety input specifications.

How to wire the safety cable to a Universal Robots or Kassow robot, or to another robot or a PLC, is described in Connect the Safety Signal.

Verification

After connecting the safety system:

  1. Power on the system

  2. Trigger the safety sensor (e.g., push the tool upward)

  3. Confirm that the robot stops immediately

Warning

If the robot does NOT stop, the safety function is not working. Do NOT operate the system; check wiring and safety configuration.

Common Mistakes

Most common safety issues:

  • Missing shared 24 V/0 V reference

  • Incorrect wiring of OSSD signals

  • Robot not configured for safety input

  • Missing safety relay (non-OSSD systems)