Addressing for Micrologix 1762-oa8?

[Skiroy]

Hello guys. I am begining an upgrade project. My employers bought a Micrologix 1400 and several 8 point Micrologix add on I/O modules. For example 1762-OA8. Now in its manual link below

http://literature.rockwellautomation.com/idc/groups/literature/documents/in/1762-in007_-en-p.pdf

Onpage 10 it describes the addressing. I dont know if Im looking at something wrong but I am not getting something. Now I am a noobie and most of my experience comes from the Micrologix 1200 which I assumed all addressing for the Micrologix series were the same. For example if I had a Micrologix 1400 and a additional output module, and wanted to address terminal 10 on the module. I would expect the address to be O:1/10.

So I am not understanding this scheme of "O0:x.0/0.
Can anyone help?

 

[sthompson]

I am not trying to sound condescending, but on Page 10 of the Manual you linked to describes each of the Address Elements quite clearly.

You can enter the Address as you usually do, and it will nicely fill it in for you.

I would suggest creating a test Applications with RSLogix500, and playing with it.

Perhaps you could be more specific about what is confusing you.

Stu....

 

[Ron Beaufort]

try this ...

right-click on an EMPTY area of the ladder display - then select Properties from the pop-up menu ... go to the Address Display tab ...

play with the settings there (particularly with the I/O Bit Display Mode) - and see how the settings affect the addresses that you see on the screen ...

basic idea: the addresses can be DISPLAYED in various styles ... that doesn't change the bit being referenced - just the way the address appears ... the "book's" scheme that you mentioned is the "formal" way of representing the address - but there are other ways which are perfectly valid too ... in many cases it's a matter of personal choice which way you want it to be displayed ...

 

[Skiroy]

Okay thank you. I know this may seem silly to you but Im still a noobie. On the MicroLogix 1400 itself there are 5 NC Inputs and 3 NC Outputs. I am assuming this means Normally Closed. I have a 1766-L32AWA which has no analog or high speed inputs and is 120V AC only inputs.

What is the purpose of these NC I/Os?

 

[sthompson]

Okay thank you. I know this may seem silly to you but Im still a noobie. On the MicroLogix 1400 itself there are 5 NC Inputs and 3 NC Outputs. I am assuming this means Normally Closed. I have a 1766-L32AWA which has no analog or high speed inputs and is 120V AC only inputs.

What is the purpose of these NC I/Os?

Your questions are not silly at all, if in doubt ask.

I am guessing the NC you are referring to is on the Input and Output Terminal Strips, on the right hand side.

If this is the case, because you have no Analog on this PLC, the NC stands for No Connection.


Stu....

 

[Skiroy]

Okay thank you so much. 2 other questions.

1. My Micrologix is a 1766-L32AWA where as the line voltage is 100-240V to power the PLC. The present voltage being used for the older PLc is either 208 or 240V. Do you see any reason not to use the current wiring vs use 120V off of the transformer used for the I/Os of the Old system?

2. This old system is an OLD PLC-2. All the outputs are going to 120VAC pneumatic valves. With the new Micrologix PLC which is Relay Outputs,I shouldnt have to worry about shunting the outputs right?

 

[iant]

As you are replacing an Old system PLC, consider interposing relays to attempt to avoid burning the PLC relay Outputs

 

[Skiroy]

Well what we have was suggested by Irby. It is bought already. Im not familiar with what interposing relays are.

 

[sthompson]

1. My Micrologix is a 1766-L32AWA where as the line voltage is 100-240V to power the PLC. The present voltage being used for the older PLc is either 208 or 240V. Do you see any reason not to use the current wiring vs use 120V off of the transformer used for the I/Os of the Old system?

I usually try and keep my PLC Power Supply separated from the I/O by running it through a Line Filter. However, according to the Specifications, it will accept 100-240VAC at L1/L2.

2. This old system is an OLD PLC-2. All the outputs are going to 120VAC pneumatic valves. With the new Micrologix PLC which is Relay Outputs,I shouldn't have to worry about shunting the outputs right?

The Specifications state the Relay Outputs are good to 2.5A, however, Outputs 8-11 are 8A Maximum for the group. This is probably comparable to the PLC2 Outputs. Have a look at the VA Rating of the 120VAC Coils, if they will require something close to, or over the 2.5A Rating, I would use an Interposing Relay.

Stu.....

PS Consider using MOVs on your Inductive Loads.

 

[sthompson]

Well what we have was suggested by Irby. It is bought already. Im not familiar with what interposing relays are.

An Interposing Relay is used to isolate two Circuits from each other. Either because they are different Voltages, from different Systems, or because higher Current is required etc.

The PLC Output only sees the Relay Coil as Load, which is normally well within its specifications.

Stu....

 

[iant]

Thanks for that Stu,
SOrry Skiroy I should have explaned it better

 

[sthompson]

Thanks for that Stu,
Sorry Skiroy I should have explained it better

No problem Ian. I am sure it has been the other way a few times.

Stu....

 

[Skiroy]

Thankx guys. Your great. This site is an amazing resource. Im supposed to be a machinst here but they are allowing me to take on automation jobs like this because Im the only one here that has any knowledge in the field. I went to a community College for Automation Technology years ago and these opportunities are the only relevant experience in my field I can get right now. I have no mentors or people to learn from,so you guys are really helping in a huge way.

Thank You

 

[sthompson]

Your welcome, I am glad we were able to help.

This is the best PLC Q&A I have found, although there are other ones on the Web that have their good and bad points.

Feel free to ask any other questions you have. So far your questions have been quite understandable and detailed. You would be surprised how often that is not the case on here.

Stu....

 

[Skiroy]

Okay couple more. The old PLC-2 was all metal frame and was screwed onto the mounting plate inside the machine control panel cabinet(dont know the terminology).

1.Anyways the mounting panel is bonded and grounded. Now I know I am going to connect the earth grouth to the Micrologix's ground terminal. But being that it will be mounted on the DIN rail,never contacting the bonded mounting panel, do I have to further ground it by running any additional wiring?

2.Secondly, my employer instead of buying a few 16 point modules bought several 8 point modules so now the entire length of the panel is going to be filled up. My concern is this puts the Micrologix 1400 so it butts up to the 120VAC I/O Wiring ducts. And the last 8 point Input module(120VAC) is butted up against the wiring duct that the main 240V wiring runs through.

So am I going to run into noise issues because of these units close proximity to these wiring ducts?