Reply To: Micrologix PLC Wiring


Hi everyone,

Just want to add my two cents…the PNP/NPN discussion is always an interesting one (…possibly a topic for a new article…any takers?). Anyhow, current sinking input modules are a common North American standard as are current sourcing output modules. Some European countries as well as Asian tend to go the other way (current sourcing inputs and current sinking outputs).

While relay output modules provide good flexibility, particularly when you want to put different voltages on them, they are not the only option. Relay output modules are mechanical devices with limited switching times and life span. Often one failing relay output means you have to replace the whole module (or at least move that wire to one of the unused spares on the existing one…that’s always fun to find out!) So it is quite common in some circumstances to use solid state transistor or triac based output modules depending on the application.

Raj it looks like you’re well on your way to getting this sorted as there has been some really feedback here. Of course if you have any more problems be sure to check back in!