Allen Bradly PLC - need some help

[jderou]

Can someone explain this diagram to me? Why are their multiple grounds on the input and why are their two seperate power sources. Can you use one common source?

Output: What does the CR stand for (coil relay?), and what about the lines next to them (resistors?). Does this mean you can only use certain types of output at each terminal? Why are their multiple +24v terminals?

I have wired PLC's before, but they weren't as complicated as this.

Thanks!

[MetLHead]

Usually multiple commons on the input side means you can have some inputs active low and some as active high. Active low means you tie +24v to the common terminal and then you apply 0v to the input to make it turn on. Active high means you tie 0v to the common terminal and then you apply +24v to the inputs (this is the way the diagram shows). With nothing connected to the inputs, measure resistance between the common terminals. If there is high resistance or an open connection, you can mix and match active low/active high inputs. Each common terminal will correspond to specific inputs. You will have to check the book further to see exactly which ones are grouped together because you can't tell from the diagram.

The outputs are sinking ouputs, which means the terminal goes to 0v when the output is on. The CR symbols on the diagram are relay coils, and the other things are probably solenoid coils. This diagram is just a example, you can connect whatever you want to the outputs as long as you don't exceed the voltage or current rating of the output.

And yes, you can use the same 24v supply for inputs and outputs. The seperate supply would be for noise immunity if you have large inductive loads on the 24v supply.

Hope this helps,
Scott

[Evodyne]

Originally Posted by jderou Can someone explain this diagram to me? Why are their multiple grounds on the input and why are their two seperate power sources. Can you use one common source? Output: What does the CR stand for (coil relay?), and what about the lines next to them (resistors?). Does this mean you can only use certain types of output at each terminal? Why are their multiple +24v terminals? I have wired PLC's before, but they weren't as complicated as this. Thanks!

In AB's Jargon "CR" is "Control Relay", but yes, it is the relay's coil being represented. The lines are not resistors. Look at AB's literature. The inputs and outputs on this module are grouped: In0-3 are with respect to the first Input common, In 4-7, to the second, etc.

You can, however, tie them together if your system uses a single common ground. The same applies to the output supply terminals. I don't know if you have the entire document that the pictures came from. I do, but it's too big to upload. I went to email it to you, but you've disabled that option. If you PM me with an email address I can send it to you. Otherwise look on the www.ab.com site: 1764-um00_-en-p.pdf. It details the groupings.

[jderou]

Thanks evodyne, I changed my profile to allow email.

Joe