Alternating Pumps using ladder logic

[zach_zachary1@yahoo.com]

Experienced maintenance tech, novice programmer. Looking for some advice on alternating pumps using ladder logic. I have a Allen Bradley 10 point Micro Logix processor that I will be using. Does anyone have an example of this they could share with me. Thank you Zach_zachary1@yahoo.com

[MrAutomation]

How do you plan to alternate the pumps? With a timer? Using a button? Do these pumps have any sort of aux (running) feedback? Any extra details? Edited January 15, 2015 by MrAutomation

[zach_zachary1@yahoo.com]

Hey. Thanks for the reply. I was pretty lite on the details. It is a duplex wastewater pump station. The pumps will be controlled by 3 floats. An off float, lead and lag. The lead float locks in the lead pump until the off float drops out. The lag float will pull in both pumps until the off float drops out. The pumps need to alternate after each cycle.

[BobLfoot]

This sounds amusingly like many a Tech School final project. Let me suggest Zach that you make the first attempt at programming it and post your work. THere are many skilled members here who can provide positive feedback and help you make it better, but few which will do your work for you.

[Crossbow]

I've done this before, with 2 pumps and with 3. But I did it in Omron and Mitsubishi, never in AB. Quick tip: Each time lead pump turns on, increment a counter. Make the timer count to 2 and reset itself. That way it will always be 0 or 1. When it's zero, use one pump as lead, when it's one, use the other.

[zach_zachary1@yahoo.com]

Little early in the year for finals! What I am really trying to avoid is pulling a bunch of wire and putting in a bunch of relays. Not looking for anyone to do my work for me. Just a few suggestions.

[MrAutomation]

Sorry, I haven't been checking here much recently. I don't know if you've done this or not by now, but here's my two bits. This is pretty straight forward. When the first high level switch trips, latch in a bit that is used to turn on the lead motor (using a simple seal-in latch rung. I'm assuming you know what a motor starter/seal in circuit looks like). Use the low level switch to drop out the latch. When the second level switch trips, latch in a bit that is used to turn on the lag motor (same as above). Use the low level switch to drop out the latch. Every time the low level switch trips, toggle a bit that determines which pump is lead or lag. That's about it. If you need help, put up what you've got started. Best of luck!