PLC design..

[cclaus]

Thanks, Dan. You've been a big help.

Yeah, I'd much rather this be fun than nerve-rattling..!
Let me put out there what I have identified and see how it rings with all you experienced guys..

Oh yeah... and you were right yesterday... When giving the boss an update at quitting time yesterday, first question was "Are those expandable?" Next question was "Think we can incorporate the whole line into it eventually?" Uh huh, that's what I thought.....

OK: I have identified either the AB Pico-GFX or the AB MicroLogix 1100 for this project. Both have much more capacity than I require to start and both are expandable out to beyond what we could possibly use with what we have now. Pico-GFX has 12 Inputs and 4 Outputs, and the MicroLogix has 12 Ins and 6 Outs. Both can add more than enough I/O modules.

 

[kdcui]

Haven't worked with MicroLogix but I know PicoSoft (the Pico controller programming software) has built in logic simulation, so you can somewhat test your logic before you toss it on the system. I found it useful when I was first learning PLCs.

 

[cclaus]

Thanks, kdcui. If I understood what I was reading yesterday on the AB site, the MicroLogix has something similiar built-in. At least I hope so.. Can anyone concur?

 

[Lancie1]

Cclaus,

Last that I knew (PLCs change every year, with new models and capabilities getting added to the line-up), the Micrologix did not have a built-in simulator. The Micrologix is programmed using RSLogix500, which does not include a simulator. There is a separate program available, RSSimulate (at considerable cost) which adds the simulation. Perhaps you are thinking of the built-in LCD screen on the Micrologix 1100. It is not a simulator, but more of an operator interface device, which allows you to modify the program or to change inputs from the screen. But remember the screen is very small, so you will not be able to see much of your program at any one time.

The Allen-Bradley Pico is programmed with the free PicoSoft, which does have a simulator built right into the programming software. This is convenient because it allows you to write a rung of ladder logic, then go over to "simulate" mode and see if it works. However, the Pico models are the low-end of the AB PLC line, one step above a programmable relay, so it does not have many of the features of the Micrologix models.

If you want some practice writing ladder logic, you could download a free copy of PicoSoft from the Allen-Bradley web site. You can then take some of the relay logic diagrams lying around your plant and convert them to ladder logic and run the program in the PicoSoft simulator.

If you want to step up to the Micrologix level, for learning purposes only, you could buy a copy of the LogixPro simulator program (about $40) from TheLearningPit.com (see the link below). LogixPro is NOT an Allen-Bradley program and it will not run on the Micrologix PLCs, but it simulates the RSLogix500 software very closely. I used LogixPro to write and test that one-rung program for you. LogixPro comes with many built-in student programming exercises, complete with graphics that simulates the machine or device being programmed. You can also make up and test your own simulations using the built-in Input switch/sensor simulator.

http://www.thelearningpit.com/

 

[wallypiper]

Guys, IMHO for this application you are over complicating it....In fact, you don't need a PLC at all.

This eliminates the need for a PLC, HMI, etc....

This was my first though as well. A $150 process controller with a "process" input and a limit "alarm" relay output is all you need. But if the boss wants a PLC, well, there you are. You'll have to duplicate a simple function that is already built into hundreds of devices already on the market in a PLC. I'd just get the least expensive PLC that has an analog input built in (1761-L20... has it, a Micrologix 1000, not sure the boss would consider the Pico to be a PLC, I'd call it a smart relay, but if he'll accept it, they also have analog inputs without additional modules).

 

[cclaus]

Lancie1 and Wallypiper,
Thanks for your inputs. The boss is dead-set to go ahead with the PLC. Cost doesn't seem to be an issue right now either... Think I will go with something in the MicroLogix line because he has already hinted at at adding all out other equipment to PLC control. And I'll "sneak" in that extra software as a needed accessory...
I want to thank all the posters that replied and offered help and advice. You guys are all life savers. (Well, job savers, anyway.)