Learning to program PLCs

[Cannery]

Thanks, I'll sure do that.

Gonna be a coupla days, I'm off to see The Big Kahuna at our parent company in Blacks Harbour, NB tomorrow.

 

[Lancie1]

Cannery,

That was a good description, and here is a first draft of a RSLogix program for a Micrologix PLC. I used a counter to keep up with the cycle, but this would be an ideal application to use a Sequencer (SQO) command. I didn't, because I think it would be more difficult for a beginner programmer to see the workings. I am sure someone here will convert it over if you wish. A Sequencer will shorten the program but make it harder to modify.

There are probably some errors, so check it carefully.

 

[Cannery]

Okay, I looked at that, and I'm pretty sure I understand everything I see there. I'll get the various I/O relays breadboarded and give that a shot as soon as I get a chance.

THANKS!

 

[Lancie1]

No problem, and glad to be of help. Please try it out and come back with your questions.

 

[Bytesize]

No, there won't be a separate misfire monitor. The combustion control circuitry will take care of that and will shut down the oil solenoid which will stop the tube blower sequence. All this unit will do is automate blowing the boiler tubes and stack, which we are currently doing manually due to the failure of the old Toshiba EX box. Our mechanical services contractor won't even talk to us about it, it's so old...

I haven't started any programming yet, between the forty-eleven other things on my plate and wanting to get a little more pre-planning done.

When I was playing with dBase, I learned a hard lesson about the dangers of building a program piecemeal and then going back and patching it until it worked.

Are you the one from NY who attended the class last week in Seattle?

 

[Cannery]

Nope, I'm from Maine and went to the class in Portland, Maine.

 

[Lancie1]

Here is improved Revision 1, deleting 1 timer and 3 rungs. Also here is a version using a Sequencer with only 6 rungs.

 

[Lancie1]

Here is improved Revision 1, deleting 1 timer and 3 rungs. Also here is a version using a Sequencer with only 6 rungs.

 

[Cannery]

WooHoo!

I used Lancie1's original program (as I could follow the logic and see how it was supposed to work) and after figuring out a couple of operator glitches on my part transferring the program from the pdf file to an RSLogix file, it works slicker than a smelt!

Breadboarded the PLC using a switch for the input and neon lamps for the outputs and ran it through the program, including interruptions to simulate the boiler shutting down before the 15 minute interval was up. Everything works perfectly.

Now I just gotta find a time to shut the boiler down long enough to install the hardware and we're good to go.

THANKS to everyone for their help. This board is an incredible resource, and you can bet you'll see me back here off and on.

 

[Lancie1]

Cannery,

I am proud that the program worked for you. I thought that you might go with the simpler version. You have proved again what I have argued here for years: Lancie1's PLC Rule #1 states that simplicity and more rungs in a PLC program is often more desirable than complexity and fewer rungs.

 

[OZEE]

Lancie1's PLC Rule #1 states that simplicity and more rungs in a PLC program is often more desirable than complexity and fewer rungs.

How true!

 

[Stationmaster]

Cannery,

I am proud that the program worked for you. I thought that you might go with the simpler version. You have proved again what I have argued here for years: Lancie1's PLC Rule #1 states that simplicity and more rungs in a PLC program is often more desirable than complexity and fewer rungs.

Lancie1,

I couldn't agree more with Lancie1's PLC Rule #1. Rungs are free, excess complexity can cost a fortune!

Stationmaster

 

[mordred]

I agree as long as those extra rungs don't form spagetti code, Good, solid well labelled layout can save a fortune

 

[Cannery]

Cannery,

I am proud that the program worked for you. I thought that you might go with the simpler version. You have proved again what I have argued here for years: Lancie1's PLC Rule #1 states that simplicity and more rungs in a PLC program is often more desirable than complexity and fewer rungs.

I'm all for simplicity...simple things for a simple mind...

Seriously tho, I agree. KISS is always a good principle. If scan time was becoming an issue and you HAD to cut down on the number of rungs, it might make sense to deal with the complexity.

 

[geniusintraining]

extra rungs don't form spagetti code

here this is what I am dealing with today...