Light Curtain Issues

Hello,

Where I work the light curtains we use are usually just connected to an input on the plc. I know I have read here where that is not allowed. In our application where we have farely small machinery (stakers, projection welders) the plc actually bypasses the light curtain during ejecting the part. Is this legal? Is there any way to do this legally? Thanks in advance

Light Curtains

You may want to browse Here
Good Luck!

Hi,

You will have to wire the light curtain through a special purpose safety relay were the curtain power supplies the relay coil and the plc input is through an auxillary contact on the relay.

Hi,

You will have to wire the light curtain through a special purpose safety relay were the curtain power supplies the relay coil and the plc input is through an auxillary contact on the relay.

Hi,

Sorry about the last one!!!!

There could be a lot more to it than just 1 safety relay with a simple hookup as above. You need to find what category (1-4) the machine is rated as and go from there. Regards Alan Case

tlvaun,

You can now use some PLC's for safety, I know Omron now makes a module with safety relays in it and I believe that AB makes a safety PLC. In order for the PLC to be used it must have safety relays which are forced guided, this means that the contacts will be open even if the contacts have welded together. You may want to check these manufactures web sites.

Mike

mitsubishi make a safety module for the fxon range. I too work with light curtains, on press machines but these use the pilz safety relays as mentioned by garryt1. I can mail some drawings if they help in any way.

Thanks for the feedback. And sorry for the lack of information. I was running late for work when I wrote the post and today (2 hours from now)I have to set up some light curtains and I wanted to get as much feedback as possible. I was going to going to hookup the light curtains just like all the rest, but I wanted to do it correctly. We use mitsubishi PLC's exclusively. I will definetly look into the safety module for the FXO series for future projects. Today I believe the PLC is an A1SH rack style PLC. Well I'm going to go study some of the documentation that some of you recommended before work. Thanks