Controllogix 1756-OF8 Wiring help

Hello everyone!*

I am having some issues with the internal wiring/wiring of the 1756-OF8 analog output card in my Controllogix L55 controller. I have just recently started using* Allen Bradley products, so please bear with me. If my memory serves me correctly, in my past experiences with other plc vendors I thought I was required to provide 24vdc+ from the power supply,*which is common to all the channels used for driving*the analog out(4-20ma) to the field device being controlled. But I can find any documentation from Allen Bradley that supports this. Can anyone shed some light on how to connect the power supply to the OF-8 card.



Thank you!!

Shane

in simple terms - the power comes through the backplane/chassis ... you don't use a separate power supply for this type module ...

make sure that you have the proper wiring diagram - and follow that ...

https://literature.rockwellautomation.com/idc/groups/literature/documents/td/1756-td002_-en-e.pdf

see page 192 - but CONFIRM that it's correct for your module ...

good luck with your project ...

Ron Beaufort said:

in simple terms - the power comes through the backplane/chassis ... you don't use a separate power supply for this type module ...

make sure that you have the proper wiring diagram - and follow that ...

https://literature.rockwellautomation.com/idc/groups/literature/documents/td/1756-td002_-en-e.pdf

see page 192 - but CONFIRM that it's correct for your module ...

good luck with your project ...

Click to expand...

Ron,
Thank you very much!! so the 24vdc is internally powered from the backplane. That would make sense. So a 2 wire analog current output device is just placed in series between the IOUT-3 and the RTN? I guess the RTN is confusing me now.

Thanks
Shane

a little experimentation will probably relieve your misgivings ...

if you've got a DC milliammeter handy - just wire that up as a "temporary" output device - and get the module's configuration all set up - before you wire up the real (expensive) output device ...

basic idea: you can wire this module up to provide a VOLTAGE output signal - or to provide a CURRENT output signal ... either type uses the same Return terminal - and you select the type of output signal by wiring to the proper current - or voltage - terminal for each channel ...

NOTE: you'll also have to do some configuration in the module's setup screens which you access through the RSLogix5000 software ...

Ron,
Great Idea! I do have a meter I will give it a try.

Thanks again for the help