PLC emergency shutdown issues
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There was originally a PLC on site, and an emergency stop button needed to be installed in the control room to enable emergency shutdown of the PLC. A two-core cable has now been run from the control room to the PLC, and the installation is complete. I am now informed that there are two PLCs at the site, and both need to be shut down urgently. And I don’t want to run another separate two-core cable; so what’s a way to use the existing two-core cable to achieve emergency shutdown of the two PLCs? Experts, please give me some advice! Thank you!
It’s better to stop together; if you go your own way, don’t be too lazy. Or, if conditions permit, turn it into a communication line hehe
A relay can be added on the PLC side, with its two contacts connected to the two PLCs respectively. Of course, diodes can also be added; refer to the Siemens PLC redundant DI configuration circuit.
If this emergency stop signal is not important, various methods can be used to divide it into two signals. If it is extremely important, it is recommended to lay another cable to ensure safety and reliability! Many units adopt a two-out-of-three approach to enhance the reliability of the emergency stop button.
I agree with the view from the second floor; it’s necessary to distinguish whether two units are shut down at the same time or separately.
Is the emergency stop signal sent to the PLC? It’s not a forced stop
If both need to be stopped at the same time, a relay can be added to achieve stopping of both circuits