IEC 2010 limit switch wiring

[captainking]

Where is the ground on this year's limit switches?
Also, is there a difference on the 13 and the 14 connections for the NO side and the 21 and 22 connections for the NC side
-Shubert

[Mark McLeod]

"NO" and "NC" beside two of the contacts stand for Normally Open and Normally Closed.
You chose one set of contacts or the other.

You connect to the contacts 13 & 14 if you want Normally Open.
Use contacts 21 & 22 if you want Normally Closed.
Wire signal to one of the contacts and ground to the other. It doesn't matter which, because a switch just completes a circuit. Direction of the subsequent current flow doesn't matter.

Most switches give you the option to appear to your code as

• an open circuit unless pressed (NO)
• a closed circuit unless pressed (NC)

There are reasons for using each. For instance, I'd use Normally Closed for a safety switch, because if the switch becomes disconnected the circuit will open and my code will stop whatever is moving to prevent an accident.