Communication

Hello
I am about to place an order for a new piece of equipment for our plant. We have pretty much the same device (a temperature control unit used with oil for part of our process) in house at the present time. The basic idea is to purchase a new unit then send our existing one's out for refurbishment.
Since the time we first purchase these units we’ve have completed a large automation project to our production plant.
Now for my question I am looking to set up some type of control for these machines through the PLC (AB SLC5/05) that is used on the extruder that the oil unit will be used with. / The Plant wide SCADA package.
The machine manufacture has told me that the available communication options are.
1) 4-20 ma input / retransmit and dry contacts
2) RS485SPI (serial port connector)
3) RS 485 (serial port connector)
4) RS 232 (serial port connector)
5) Ethernet IP via modbus RTU (RJ-45 plug)
We have 5 extruders that are pretty much identical and I would like to keep the ability to be able to freely move these oil heater from extruder to extruder with no or very little setup required (don’t need another item for 3am phone calls)
I do have experience with 4 – 20 ma signals and dry contacts (The extruders currently have analog input cards in place). We do have some modbus serial communications going on, each extruder's SLC has a Prosoft modbus card. Where one channel is used to communicate with the A/C Freq. Drives and the second channel Discreet PID loop controllers. I do however consider serial comms as one of my two greatest weaknesses and find myself more than a bit uncomfortable with the serial comms options as well as that the serial comms option adds about $1000 - $1200 to the cost of the unit. However the level of control using serial comms is much greater than the analog option.
I suppose what I am looking for is your opinion on which comms option you would select and what your reasoning behind your selection is.
Thanks in advance for you help
Michael

Have you looked at AB's Micrologix1500 LRP.

It Can do everything on your list. Even Modbus with out an expencive SST or prosoft adapter.
Call up local rep find out how much it is in your area. Then go with which ever com medium you are most comfortable with.

I'm sorry I think the way I worded my post may have been a bit confusing.
My extruders are already currently controlled by an AB SLC 5/05 that is communicating via ethernet to our plant scada package.
The control system that is coming with the new oil heater is complete from the manufacture and they seem either unwilling or unable to make any type of modification to their machine.
The options I have laid out in my first post are what the oil heater manufacture has available for communication and control of their machine. My question is which of those 5 options would you choose and why did you pick that option.
I don't know if this clears anything up or not but I hope so.
Thank you for your rely Allan I really do appreciate the help
Michael

What information do you want to get from the oil temperature controller? What type of data and what control signals do you want to send to it? If all you need to do is send temperature setpoints and monitor actual temperature, then the analog signal is probably the way to go.

You're correct that serial communications gives you more flexibility. If you're going to be gathering a lot of data, it might be worthwhile to use this project as the vehicle to learn how to do it. It's a skill that looks good on your resume.

Just out of idle curiosity.... what type of processor is the new equipment coming in with? There are quite a few devices that have the same communication options that the manufacturer gave you, but it might be easier to pick the correct option if you knew the specific device involved.

Thank for the responses
At this point the only items I really need to know and control are.
1) Ability to adjust setpoint temperature
2) Actual Process temperature
(With these two items I can created my own deviation alarms within the PLC. I'm figuring that if any other problems with the unit occur the deviation alarm will make us look at the unit)
3) Start and stop the machine.
Sterling, Inc. manufactures the unit
here is a link
And is a model 2016/2026 Royal Series Upright Oil unit. with a M2B+ controller.
The last piece of information is that I need to order either this oil heater today or spend the money for support for our Scada software. Our financial quarter ends today and I'm trying to make these two purchases in different quarters.

Thanks again
Michael

Steve Bailey said:

If all you need to do is send temperature setpoints and monitor actual temperature, then the analog signal is probably the way to go.

Click to expand...

I agree wtih Steve - it sounds like you don't need the added flexibility that the communications will give you, in which case, I would recommend the analog signals only. That seems to match with your skill set, gives you what you need from the process, can be done (relatively) quickly and easily, and costs less!

If you have time or money to spend learning how to write/work with serial communications, then it can be good experience for you to pick up. If you go that route, you can do comms through your SLC CH0, but you might want to consider using a basic module instead - I personally think the comms interface is much more intuitive that way.

Good luck,

Marc