Safety circuit inputs

Hey everyone,

I have a safety controller (Omron G9SP) for 2 robotic cells that I need to add safety mats to. The device has only 1 free input so that's not going to work as is.

I'm looking to install an add-on module of non-safety I/O and was wondering what I can offload to the non-safety I/O. I know reset buttons are not required to be safety rated, but what about EDM (external Device Feedback) signals? If they don't need to be safety it would open up enough inputs for me to make this work.

Also, as an aside, I am using these mats as a "Start inhibit", not as a stop function (The area is barrier guarded with locking gate switches). Does that play into whether I could use non-safety I/O for the mats (I'd rather not do this, but...)

Thanks in advance!

Chris.

Chris,

safety devices need to be two channel, so you need to free up another safety input. The feedback signals from the safety cut out device need to be on a safety input as well, though currently one channel is sufficient as far as I know.

Hope this is helpful. More details can be found in machine safety directive and Schneider Safety Handbook (free to download) or other manufactureres handbooks.

Some items like e-stop buttons & gate switches could be placed in series if they are on individual inputs currently. Makes determining which e-stop or gate is opened harder but you can use a third wire and non-safety inputs for this if needed but it does decrease the number of safety inputs needed drastically.

Cheers

Another option is to add a specific-purpose safety relay to the circuit to handle the mats. It has a set of dry contacts that can be used for your last free input.

url didn't work. Just try googling "safety relay."

sparkie said:

Another option is to add a specific-purpose safety relay to the circuit to handle the mats. It has a set of dry contacts that can be used for your last free input.

url didn't work. Just try googling "safety relay."

Click to expand...

I'm under the assumption that even when doing this, you'd need to maintain 2 channels to the safety controller to stay at the appropriate CAT level.

I think at the end of the day I'm just going install a 2nd safety controller and have 2 signals running between them. This went from 2 mats to 5 mats, as these things tend to balloon into orbit.