PLC/HMI combo to use 2

[tona2008]

Hi everyone,

I was given the task of automating an oil heated press operation. The hot press needs two PID loops one to control the temperature and one to control the pressure. I have programmed the SLC 5/03 PLC before but only to control discrete outputs to open/close valves, alarms etc. Never dealt with analog signals. I need some guidance on which would be the combo PLC/HMI combo to use that will be the easiest to program and configure. Are there any PID modules on any PLC manufacturer that I can use to control the temperature and pressure? Can they be interphased to an HMI so that I can start the loops from an HMI screen? Does it have to be a PLC?
Any help will be appreciated.
Thanks,

 

[roydm]

I suggest you check out Opto22, they have inexpensive hardware and free software. I have used their product on a couple of jobs and found it works well. I have also used AB and found their monitors to be lacking.
Regards
Roy

 

[xJAyx]

There are really too many options to list, but for this application your best solution is probably a stand alone PID controller. There are a lot of options, but most of them work well, and you can get dual loop controllers from most maufacturers. I would check out yokogawa, eurotherm, omron, watlow, love etc. They will be heaps cheaper than any PLC/HMI combo, plus there is very little configuration to do, so you'll save on time on the design/programming side as well as the installation side.

Are these two loops (temp and pressure) interrelated? Maybe you should be looking at cascaded or other multi loop control strategies.

 

[tona2008]

xJAyx

These 2 loops are part of a recipe. The temperature loop and pressure loops should be started simultaneously. This should be done on a single "cycle start" switch. I'm trying to prevent the operator from forgetting to start either one of the loops. This is why I'm trying to use an HMI where I can create a recipe and download it to the controller. With a soft internal switch start both loops at the same time. I know it can be done with a PLC but it requires a lot of programming.

Thanks for your suggestions,

 

[NWBeaver]

Is this intended to be a stand alone system, or is it part of a larger system. By wanting to create and download recipes it sounds like a PC of some sort would be involved, to store the recipes.
A PLC such as the SLC 5/03 for example, has a built in software PID loop instruction, and just requires some analog I/O. It could also be used to store your recipe values, which could be accessed by a PanelView perhaps, removing the need for a PC.
PC based HMI and recipe control can get expensive, so unless it was part of a larger system, I'm not sure I would go that route.

 

[tona2008]

NWBeaver,

Thank you for your reply, It is a stand alone system. This press is for use on our R&D department. This is why we don't want to spend too much money on this project. How difficult is it to program PanelView to be able to access this PID loop instructions?

 

[NWBeaver]

Not difficult at all, the SLC PID instruction uses "N" registers. You would just need to create a Control Block of addresses such as N10:0 thru N10:22, for example.
In this example, the PanelView would then access N10:2 to read the Setpoint value.
The SLC instruction set manual maps out all the registers for you.

 

[xJAyx]

There are stand alone controllers that have recipe control, as well as hmi's that have built in recipe functions. I'm sure you could get a yokogawa 2 loop PID controller with recipe control.