Seeking Advice..

This is my first post but I have been following through this forum for awhile and gathering knowledge. I am fairly new to PLC, but have just recently completed a course at my college where I used a software known as Logixpro. A great piece of work if I might add, very helpful but I don't know if ladder logic can help with what I am trying to achieve for this personal project I am doing. Below is my following question but I will explain a little on what I am trying to do.

I have 2 pumps & 4 switches also know as "floats" to determine different water levels within my tank.

The float names are Off Float, On Float, Lag Float & Alarm Float, respectively.

When the Off Float is off, meaning the water level is stable then of course, both Pumps #1 & #2 are off.

Here is where my problem comes in:
When the On Float comes on(which would be a water level slightly higher than the Off Float) I would like to have Pump#1 & Pump#2 Alternate between each other whenever the On Float is triggered. I purchased a Digitec PLC which the software was based on Logic Gates and not Ladder Logic. I could not configure a type of alternator using Logic Gates. Even after my class this past summer, I'm still struggling on how to configure an alternator using Ladder Logic. I still feel it would be easier to do in Ladder Logic rather than Logic Gates but I am struggling with solving this. Any advice or possibly a lead into the right direction would be grateful.

The Lag Float when triggered,(a water level higher than the On Float) sets both Pump#1 and Pump#2 on at the same time.

The Alarm Float of course comes on if both pumps have failed to bring down the water level.


I have a circuit but not sure if that will help. My main problem is of course the alternating of the pumps each time the On Float is triggered.

Any advice would be great!

Artronix,

Welcome and happy hunting to you!

Even after my class this past summer, I'm still struggling on how to configure an alternator using Ladder Logic. I still feel it would be easier to do in Ladder Logic rather than Logic Gates but I am struggling with solving this. Any advice or possibly a lead into the right direction would be grateful.

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Alternator logic is fairly common. I have uploaded a LogixPro file that has 10 different methods to create an alternator in PLC ladder logic. I think there is a copy in the PLCtalk.net "Downloads" section. Click on the yellow "Downloads at the top of your screen, and look for the "ALTERNATOR METHODS.pdf" file in the Allen Bradley PLC section.

Here is an updated version in picture format and also the ZIPped LogixPro program so that you can test the methods for yourself using the LogixPro "I/O Simulator". Set the first switch on I:1/0 to be a momentary normally-open pushbutton by right-clicking on the switch contact 1 time. I:1/0 controls 9 of the 10 methods. Method #10 actually will set up to 16 bits with any 16 input switch in Input I:3, so use I:3/0 to I:3/15 to alternate bits in Output word O:4.

I have a circuit but not sure if that will help.

Click to expand...

Sure it will help. Post it here!

I am not familiar with Digitec PLCs.
A google search Revealed little. Are they known by another name?

I would probably just use a counter that when it comes on it counts and if the counter is 0/1 that pump would come on. Then if the third float comes on both are on.

You might want to have an alarm if you get a situation that isn't possible. As in first and last float on but the second float is off... or something like that.

Also, you might want to have some kind of pump time off delay so that the pumps don't just stick at the on/off liquid level. That might get annoying if your program turns on and off a lot with out some kind of hysteresis.

Liam, It could be this Digitec:

http://www.digitecindustrial.com/circuits.html

VAN said:

Also, you might want to have some kind of pump time off delay so that the pumps don't just stick at the on/off liquid level. That might get annoying if your program turns on and off a lot with out some kind of hysteresis.

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It is more common to employ "de-bounce" functions on the floats (level switches), rather than using the pump(s) to force the level past the float switch-point. Suitable ON and OFF debounce times can be commissioned to provide hysteresis (filling and emptying can be, and usually are, at different rates).

Lancie1 said:

Liam, It could be this Digitec:

http://www.digitecindustrial.com/circuits.html

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Lancie these look like logic blocks, rather than a programmable system.
Maybe Digitec is an acronym..

Maybe it is this Marsh Bellofram Digitec. It uses Function Block programming and maybe that is what Artronix meant by "software was based on logic gates".

http://pdf.directindustry.com/pdf/m...mmable-logic-controller-plc/11788-148229.html


Hmmm....Is it too late to put it back in the box and get a refund?

Do I Go In The Executives Closets

Lancie1 said:

Maybe this Marsh Bellofram Digitec then. It uses Function Block programming and maybe that is what Artronix meant by "software was based on logic gates".

http://pdf.directindustry.com/pdf/m...mmable-logic-controller-plc/11788-148229.html

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Yes, I think that's the one Lancie.
Will download the software tomorrow and have a look.

daba said:

Do I Go In The Executives Closets

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Yes, you are really getting into the whole acronym thing.
You could become the official forum Acronymmer.

You could become the official forum Acronymmer.

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That would have to be the "OFA"

Lancie1 said:

That would have to be the "OFA"

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Thank you Lancie, I will check those out. As far as uploading the circuit, I will have to do that tomorrow since I am presently at work. Digitec was not my best option it was just at a reasonable price and I thought the function block would be easier for me since I am familiar with that rather than the ladder logic at the time. I should possibly purchase an Allen Bradley I suppose. Thanks again!

Lancie1 said:

Maybe it is this Marsh Bellofram Digitec. It uses Function Block programming and maybe that is what Artronix meant by "software was based on logic gates".

http://pdf.directindustry.com/pdf/m...mmable-logic-controller-plc/11788-148229.html


Hmmm....Is it too late to put it back in the box and get a refund?

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That is the exact one aha. No refund since I've had it for nearly 6 months just haven't had the time to play with it until now.