How can one acheive compliance with EN-954-1 category 3, without using a safety module in the PLC? Is there is any other way to acheive such compliance for connecting Emergency stop, and critical signals to a PLC system?
Of course there are ways to achieve compliance to cat 3, even cat 4, without safety PLCs. Cat 3 basically means that a single failure of the control element shall not impede the safety funcvtion of that element (therefore 1oo2 technology) and that the single fault should be detected within a single safety function cycle (therefore monitoring of the safety cycle). Safety relays (such as Pilz and others manufacture)are a common electromechanical technology used to achieve compliance.
Follow the following link to HVGB's pdf on "Safety-related control Systems in accoedance with EN 954-1". It is a precious ressource.
Hope this helps,