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Enabling Switch with an Integrated Safety Controller and a POINT Guard I/O Safety Module Safety Function Application Technique
Shorts to 0V DC (and wire off) are seen as an open circuit by the safety input module, and the controller reacts by dropping out the safety
contactors. If the inputs remain discrepant for longer than the discrepancy time, then the function block (DCS or DCSRT) in the controller
declares a fault. Only after the fault is cleared and the faulted input device is cycled, does the function block reset.
The final control device in this case is a pair of 100S safety contactors, K1 and K2. The contactors are controlled by a POINT Guard I/O safety
output module. The contactors are wired in a redundant-series configuration. A feedback circuit is wired through the normally closed
contacts and back to an input on the safety output module to monitor the contactors for proper operation. The contactors cannot restart if
the feedback circuit is not in the correct state.
The system has a reset button for resetting faults. There is a jog button on the enabling switch that the control system uses to start motion.
The reset button, the jog button, and the contactor feedback circuit are all wired to the safety input module in this example. This
configuration is not required for functional safety. These inputs could be wired to a standard input module.
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Rockwell Automation Publication SAFETY-AT125C-EN-P - February 2022
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