Created Date: April 17,2012

Created by: Adisharr

I figured it was possible that I was interpreting it incorrectly. The specifications for the C0-08NE3 for example state;

"Maximum Input Current 5mA@27.6 VAC/VDC ". I didn't understand if that meant the maximum current possible carried by the signal input wire.

It is kind of an odd way to state the maximum. They should really list the maximum voltage instead as that's much easier to figure out.

Created Date: April 17,2012

Created by: Do-more PE

When you are figuring the current draw from the supplying device, you need to know how much the input point will consume. Hence the current listed for each point.

This is also helpful to know when a supplying device's leakage current is specified. Occasionally the input will not consume enough current to overcome the supplying device's leakage current so the input point will not shut off properly. In this case you need to know both the current consumed by the input point as well as the leakage current of the supplying device in order to calculate the proper resistor to draw enough current to shut the supplying device off so that the input point will operate properly.

Created Date: April 17,2012

Created by: Dean

I think it is my ignorance more than anything that is the problem here. These signal wires are at present driving relays, I have been tasked to add some more control to these signals, so I thought I would shoehorn a CLICK in series between the signal source, (an AB controller), and the relays. Using an clamp ammeter, I checked the current draw on the wire as it is presently in use. I didn't think it through enough. Once I tie it the CLICK inputs the CLICK input impedance as you say, is what determines the current.

Created Date: April 17,2012

Created by: bcarlton

Now that you have described the application you should place the inputs of the PLC in parallel with, not in series with, these signals. Assuming, and check this out please, that all these relays have one side commoned, that common would be attached to the common of the Click inputs. Then each relay's hot side would tie to its own input.

An alternative would be to modify the AB program (assuming you can get at the program and that system has, or can be modified to, the additional I/O, if any, that you need.

Created Date: April 18,2012

Created by: Dean

Voltage is equal across parallel :o. If my high school teacher saw this he would wonder why he wasted his time. All of the relays share a common. The AB controller is locked out to us. In my case that's probably a good thing. I learned about snubbers on another project I worked on, and plan on using them. I thought a small breadboard with the snubbers soldered on it would be a good idea. Thank you all for your help and advice. I'm sure I'll be back.

Created Date: April 18,2012

Created by: Dean

Okay I spent the morning trying draw up how to wire this rig up in parallel, and I can't get my head around it.

Here is how it is now.

AB controller 24 VAC voltage outputs to relays. load side of relays to equipment.

Here is how I want it.

AB controller 24 VAC outputs to Click inputs, Click 24 VAC outputs to relays. Load side of relay to equipment.

I want the AB controller to have overriding control as it has inputs for motor starter overloads etc, that would need to interrupt the action of the Click PLC. In other words if the AB outputs/Click inputs go low all the Click outputs go low. That is how I have designed the CLICK ladder. Does that make sense?

*EDIT* I have attached a quick schematic. Does this make electrical sense? *EDIT*