2 pump control with plc

[antontobias]

hello,

i am a entry level student studying plcs. i was wondering if anyone could help me with a problem.

i need to control 2 pumps. using a pressure switch as a set point for low tank pressure only one pump can be on at a time to raise pressure, they must operate in an alternating sequence. and if one fails the other must turn on. both pumps cannot run simultaneously. if it can be done without a timer that would be better.
i searched around and found flip flop solutions but didnt know how to tailor it to my problem.

can someone point me in the right direction to a ladder diagram

thanks alot.

 

[Pierre]

First, dear antontobias , welcome to this site and bravo for 1, registering and 2. stating up front that this is a student question. (although we would have guessed)


If you want to be the first to do it wright, follow my advices.

A. You have writen some details about your task. Now write them in a more professional way. Write each and every steps of your task (lets call it a sequence) on one line.

Only one action per line.
Only one condition per line.
In sequence.

You will have maybee twenty to thirty lines. No big description here.

Something like

10 "Pressure switch = low"
20 "Pump Starts"
30 "Pressure switch High"
40 "Pump Stops"

Lather, rince , repeat !!!

Take good care of what you write. This is not your prgram. Do not try and making this a program.

Once you have completed this...

Add a full description to every line. Like what is the incoming signal and how it is detected, how it transit from one state to the other.

You will have writen you process flow. It will be the very base of your program.

Once this is writen, post it here, a question like "Where the heck should I start or What should be my first line of code?"

If you had registered under a girl name and you have asked to help you with a project for you church then the help would have been immediate. To bad!

Showing the boys that you have worked to get this process flow will, for sure, earn you much respect and help.

Hope to see you back with more.

 

[rsdoran]

To add a little more for thought to what Pierre has said. When Pump1 runs add a bit to state Pump1_WAS....ie pump1 ran last, use this to set pump2 the next time pressure switch is low. Set a Pump2_WAS bit and unset the Pump1_WAS bit.