PLC Hardware Specification/Design

DazJ · May 17, 2018

Hi,
I'm looking at installing a PLC in one of our machine panels and would like some help/guidance on product selection.
I've been looking at the Allen Bradley Micro800 series but can't find the one that matches what I'm looking for.
I would like the main CPU in one panel (approx 10 inputs/6 outputs) and a slave unit in a different panel (approx 6 inputs/4 outputs), the 2 panels are around 20-25metres apart.
It's mainly the communication side between the main CPU and slave unit that I'm struggling with.
Any help will be greatly appreciated.

alive15 · May 17, 2018

1764-l24er-qbfc1b for main CPU and 1734-aentr for slave unit or extra i/o which will be 25 meters away. Use ethernet to connect between the two. The main CPU i recommended has enough local i/o on it to meet your needs. For the slave unit, you will need two cards (1734-ib8 and 1734-ob8), the ib8 has 8 inputs, the ob8 has 8 outputs. Works great. Very easy to set up communication between PLC and remote i/o. It will all run under 1 master (main cpu). Pricey $$$ however.

Maybe describe your budget for the project?

dmargineau · May 17, 2018

alive15 said:
1764-l24er-qbfc1b

1769-...CompactLogix 5370.

The Micro800 controller family does not have Remote I/O capability; the configuration software (CCW) is, however, free of charge.

The CompactLogix controller platform has Remote I/O capability, however, the Studio5000 configuration software is not free.

For a small application such as yours I would use the 1769-L24ER-QB1B 5370 CompactLogix controller ($2060.00 List; 16 DIs and 16 DOs on-board).

As for the Remote I/O, as alive15 suggested, I'd use the Point IO series.

1734-AENT 1-Port EtherNet I/O Adapter Module $530.00 List
1734-IB8 24V Dc 8 Channel Sink Input Module $119.20 List
1734-OB8 24V Dc8 Channel Source Output Module $134.00 List

This would be the least expensive Allen-Bradley setup allowing Remote I/O provisions with some 33% expansion provisions.

DazJ · May 17, 2018

The budget would be approx £500-700. I am not tied down with Allen Bradley if there is any other manufacturers that would offer a product line to suit.
I'll take a note of the units mentioned, thank you.

ASF · May 17, 2018

^^what dmarginaeu said, except use a 1769-L16ER-BB1B PLC instead. Still 16DI/16DO, but much cheaper.

[edit]: that budget is going to make things harder. Maybe look into automation direct - not sure that you can do remote I/O but maybe you can just use two PLC's and communicate via modbus TCP

AustralIan · May 17, 2018

Chuck a pair of micro820's at it! MSG instruction over Ethernet.

Bullzi · May 17, 2018

If you cant swing the CompactLogix solution then I would look into the Automation Direct Productivity 2000. It has True Remote I/O capabilities. Programming Software is free and it is pretty good.
You are looking at about $550 for the main rack and $500 for the remote rack. That is based on DC inputs and outputs.
I have only used this PLC on one project but was very happy with it overall and for the price I think the P2000 is a very powerfull option.

DazJ · May 18, 2018

I think I'll be listing the Allen Bradley Micro800 units on the project plan.
I've had a quick look through the manuals and it doesn't look like it needs any extra hardware for communicating between the 2 units.
Also, they are only £243 each for the Micro820 so within budget too.

Do all of the Micro800 series controllers have the capability of adding a slave module via ethernet?

dmargineau · May 18, 2018

Only the 820s, 850s and 870s have Ethernet connectivity.

AustralIan solution will not add a "slave module over ethernet".

You will have two separate CCW applications running on two separate CPUs; the CPUs will communicate via EtherNet/IP Explicit Messaging; each CPU will control its own I/O. Explicit Messaging data and applications' logic will implement the 'Master/Slave' relationship.

DazJ · May 18, 2018

With each CPU controlling it's own I/O, would it still be possible to have an Input from the 1st CPU activate an Output on the 2nd CPU?

AustralIan · May 18, 2018

Yes.

You would do something like

Code:

PLC1 code:

Input1            SendThistoTwoUSINT.0
XIC -------------  OTE  --

PLC2 code:

         (Periodic MSG, Data table read from PLC1, rmeote tag SendThistoTwoUSINT, local tag TwosUSINT)
------------------ MSG --

TwosUSINT.0         Output1
XIC -----------------   OTE --

You can even include code like handshaking, what to do when comms fails, additional logic etc.

dmargineau · May 18, 2018

Yes, kinda...

1. The 1st CPU Input data needs to be mapped via 1st CPU application logic to a local memory location.

2. Said 1st CPU memory location data will be 'inserted' into a Explicit Messaging Write instruction via 1st CPU application logic and then sent to a 2nd CPU memory location via EtherNet/IP protocol.

3. 2nd CPU will read the memory location written by 1st PLC and relate it to its own Outputs via 2nd CPU application logic.

It will probably work as intended even if it is quite convoluted; obviously, you will need to implement some sort of surrogate 'classic' I/O functionality via communications monitoring and bi-directional feedback via both CPUs' applications' logic.

P.S. Ian beat me to it...

DazJ · May 18, 2018

Thank you, If the project goes ahead I'm sure I'll be back in touch for assistance with the program side.

JaxGTO · May 18, 2018

Just an FYI, I have done 5 jobs with the Micro 850 and I can honestly say I hate them! The CCW crashes on a regular basis. Online editing is a joke. The whole up/download with logical values will screw you over eventually.
If you program is going to be more than 100 rungs, use a better PLC. You will be much happier in the long run.

LoganB · May 18, 2018

Even our Rockwell distributors have warned us away from the Micro 800 lines. Better to spend the money on the L16 and save yourself a headache. I've always worked with Rockwell so I can't attest to the Automation Direct stuff but I've heard good things.

PLC Hardware Specification/Design

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