Temperature controller interfacing with a CompactLogix

RonJohn

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I have a customer with an application that will utilize a CompactLogix PLC along with the need for on/off temperature control. The application is otherwise very basic, all digital I/O and no HMI. But we need to be able to read the current temperature into the PLC and change the setpoint from the PLC. Also, pricing is of utmost importance to them.

Since they are looking for a cost effective way to run this setup, so I'm thinking maybe a standalone temperature controller with Ethernet communications would work best. Ethernet I/P would be optimal, but I havent found a controller with this capability yet.

I found that Newport makes a controller with Ethernet, but it's not Ethernet I/P. The 1769 L1 processors do support Open Socket Ethernet, so I think I can make this work. This is a new area for me so I've begun to do a little bit of homework.

Does anybody out there have some helpful experience with this type of setup that they could share? If there's a better way to skin this cat, I've got a listening ear as well. Thanks in advance.
 
You could use a standalone temp controller with analog in (4-20ma) for RSP (remote setpoint).
You could also do analog in for PV (process variable) and send that from PLC also, after converting the temperature to 4-20ma in the PLC.
You can bring the the CV (control variable - % power) through the PLC to the device. This will allow you to interrupt % power for safety or control functions and/or to go into manual mode from the PLC.
 
You could use a standalone temp controller with analog in (4-20ma) for RSP (remote setpoint).
You could also do analog in for PV (process variable) and send that from PLC also, after converting the temperature to 4-20ma in the PLC.
You can bring the the CV (control variable - % power) through the PLC to the device. This will allow you to interrupt % power for safety or control functions and/or to go into manual mode from the PLC.

Thanks Nathan. The downside is that if I do the temperature control in the PLC, I'll have to add an HMI plus analog I/O that wouldn't be necessary otherwise. I only have digital I/O currently.

I'm thinking a standalone temperature controller will be much more cost effective than purchasing all of those other parts.
 
Yes, you can just use a standalone controller.
I suggested the use of the analog I/O interface between the controller and the PLC because you stated in your original post that you wanted to use the PLC as an interface to change the Setpoint and were interested in an Ethernet interface.
 
Eurotherm nanodac controllers support EtherNet/IP. They are nice, but not the cheapest controllers. I also stubled across some Watlow controllers that support EtherNet/IP, but we've never used them.

FYI, for some industries re-transmitting temperatures via analog signal isn't allowed.
 
@ RonJohn you can use these temperature controllers from watlow link is below, and it communicates over ethernet/IP. I used it with a logix 5000 family processor and although i did not do any PID looping with it all those parameters are available. I also think i made an add on instruction for it as well.

Mark Timm described that ethernet/IP can be added to it but also others protocols can be used depending on your wiring.


http://www.watlow.com/products/controllers/ez-zone-pm-express-pid-controller.cfm?famid=15
 
use a simple thermostat and have it in series with the PLC output, this will give you sort of HMI and you do not need analog channels in your PLC (as they are expensive)
 
I installed more than 20 eurotherm temperature controllers to a Control logix plc using profibus interface some years ago. No problem at all. I'm sure that there is also a profibus interface for the Compact logix.
 
H
I have used the Watlow over Ethernet and I found it very good and easy to setup and use. I used it with a micro logix 1100 and this was for cost reasons also

Donnchadh
 
@ RonJohn you can use these temperature controllers from watlow link is below, and it communicates over ethernet/IP. I used it with a logix 5000 family processor and although i did not do any PID looping with it all those parameters are available. I also think i made an add on instruction for it as well.

Mark Timm described that ethernet/IP can be added to it but also others protocols can be used depending on your wiring.


http://www.watlow.com/products/controllers/ez-zone-pm-express-pid-controller.cfm?famid=15

dbh6, I'm curious to know how you configured the Logix5000 program to communicate with the Watlow controller. Did you add the controller to the I/O configuration tree in the Controller Organizer? Did you use MSG instructions to get info to/from the controller or were there controller tags already assigned for the unit?

When I looked at their literature, it stated Ethernet I/P/Modbus TCP. That "/" inbetween the two has me wondering if it is actually Modbus TCP messaging over Ethernet and not straight up Ethernet I/P. I believe the latter would allow the controller to be added to the I/O config tree. This would be preferred, eliminating message instructions.
 

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