Introduction and newbie question

Hi All.

I'm Ian, from Australia, and while getting long in the tooth, have not had a lot to do with PLCs. A lot of experience with complex logic and analog control with DCS, but only minor dabbling with Omron, AB and, way back, Square-D PLCs.

I'm involved in the early stages of design of a small process pilot plant, probably no more than 100 - 120 I/O, 60/40% discrete/analog. Will involve a dozen or so VS drives needing precise speed control. Planning on the VSDs looking after themselves re. speed control via built-in PID and speed sensor inputs, with remote setpoints sent via comms (Modbus?)

So to the control system. Project is too small for even entry-level DCS costs but, due to my DCS bias towards single integrated systems, I'm looking at the Red Lion Graphite system. Their loop controllers, comms interfaces and HMI have been around for many years and seem well regarded.

Graphite control not so well established but seems to offer most IEC61131 options (but not SFC) and a reasonable I/O options with the E3 modules. And all tightly integrated with the HMI and comms capabilities.

And free software! No exorbitant licence fees! (I must have some Scots ancestry back there somewhere...) As it's just a small pilot plant, we won't necessarily be locked into using RL should the full size plant go ahead but it would be handy if the control logic were portable. I've already started playing around with the Crimson 3.1 software and it doesn't seem too daunting.

So may I ask: What is the general opinion of RL Graphite, re. both hardware and software, ease of use & reliability (preferably from those with first hand experience)? Will the IEC 61131 control logic be readily portable to other systems?

Personally I would avoid using the Red Lion Graphite HMI to act as the main controller for the process. Sure they can take IO modules but in my opinion would be more geared towards 'edge' solutions, just to pick up a few IO points to re-transmit to a main (PLC) controller.

I would use a separate PLC and still use a Red Lion HMI. They make great screens.

To keep costs down I would go with an AB Micro 850 PLC. These are reasonably cheap but full-featured and can talk to most anything with on-board RS485 and Ethernet for Modbus, Modbus TCP or explicit Ethernet/IP messaging. The software (Connected Components Workbench) also has a free version and is quite powerful, offering ladder, function block and structured text, although can be a bit slow and cumbersome to use compared to the likes of RSLogix / Studio 5000 from AB.

Personally I would also recommend against doing PID control using the VSD's themselves except in the most basic of stand-alone applications. I would take all sensors and process variables back to the PLC and use the PLC to do PID speed control and send the speed references to the drives over comm's. If you use AB drives then there is already sample code to get you up and running. You gain a lot more flexibility by having everything come back to the PLC.

Anyway, that is my 2c. I'm sure you will get a few differing opinions!

Cheers

Thanks Brenden. Will investigate your suggestions.

The micro850 is too small.

IanfromOz: probably no more than 100 - 120 I/O, 60/40% discrete/analog

2080-sg001: "These controllers can support up to four expansion I/O"

So 4 * 2085-IF8, 2*2080-IF4 + 3 * 2080-IO4OB4 gives you 40 analog and 72 digital.

I had done one project on their Edge controller. There's a slight learning curve as with all new (to me) product but wasn't bad. It handles a lot of protocols with ease. Yes, I would be comfortable with it being the main controller. It's probably one of the lowest cost PLC with HMI that handles all the standard programming language.

To me, unless you are going with the first tier PLC (compactlogix or above), you are not going to get much more stability. However, I don't have hard # to back up that.

AustralIan said:

The micro850 is too small.

IanfromOz: probably no more than 100 - 120 I/O, 60/40% discrete/analog

2080-sg001: "These controllers can support up to four expansion I/O"

So 4 * 2085-IF8, 2*2080-IF4 + 3 * 2080-IO4OB4 gives you 40 analog and 72 digital.

Click to expand...

Yeah you are right about the 850, the Micro 870 should handle it fine though.

Double the amount of expansion cards plus front plugins.

Spectrum Controls also make some nice high density cards for this platform.

Unitronics have some nice PLC/HMI combos, free software, good support and easily integrated,
Worth a look for you...

Thanks to all who have made suggestions. I'll check out all the options mentioned and see how well they may fit my application.

Good to know there's so much help and goodwill available as I step outside my previous 'comfort zone'.