The SmartCNX controller has two solid state relays (relay 2 and relay 3) similar to those found on the SmartTouch and SmartDC boards, but the pinout is a little different. The switched connection is placed next to a power output rather than a common.
This is convenient if you want to power and control a 24V accessory. As an example, to control a relay do this:
The fly back diode protects the SmartCNX controller from voltage spikes caused by switching the coil in the relay. It’s a good idea to use it for most accessories. Almost any diode will work in this situation. Something like a 1n4007.
The +24 line will supply up to a maximum of 2A to power an accessory. The max for the whole SmartCNX controller is also 2A, so if photo eyes or other accessories are being used they contribute to the 2A limit.
If, on the other hand, one wishes to control the input of a third party device, the relay should be connected like this:
When Relay 2 is energized it connects the input terminals of the 3rd party device through the SmartCNX ground plane. It doesn’t have to be the Input 3 COM, any COM connection will do.
When set to “Disabled” the relay normally open (NO) contact is energized by default, allowing the relay ports to be used as auxiliary power for a 24V accessory with the NO terminal acting like a COM.