sump pump help

Hi everyone,

Okay here is my question,Im trying to write a program with AB logix ladder.I want to control a sump pump at work with a slc500.I want it to turn on when the water level is at three feet in the pit and shut off at one foot.Im going to put in a manual on-off switch and alarms for high water,this part I have figured out.But Im not sure what to use to control the levels?

Is this real or a school project?

Think compare ( GEQ/GRT) instructions if it's for school.

Do you have an analog input that represents the level?

I am not sure the question is regarding software or hardware,

Hardware

If your water level criteria is not very stringent, a couple of float switch will do the job, else go for analog options

Software

As Mickey mentioned if you are going to analog, then all the compare instructions are there to help you.

But if you are going with digital options, then a basic ladder - 'if then else' is good enough

Regards

Sump pump implies a small unit, and float switches are the normal way to do this. If you use a level or pressure transmitter it will cost more for marginal benefits.

You can get goodies like float switches from:
http://www.usabluebook.com/

But I'm not sure what to use to control the levels?

Click to expand...

You only have mentioned ONE device that can control the levels: the sump pump. That is what your PLC output should control. The rest is logic details of how to make the pump go ON at high level and go OFF at low level. HINT: Use a pump seal-in contact.

(As with most beginners, you are concentrating on the input devices, and totally ignoring the one thing that you have available to perform the job, do the action, pump the water.)

Think in reverse: The water has been pumped out. How did I turn ON the pump when the level was high? How did I keep the pump running when the level was not high? Now how did I turn OFF the pump when the level was low?

The pump output is implied; but I see what you mean, Lancie1. A struggle over inputs, when there is only one output, "the pump" given.

Using level switches is the easiest part. It's a simple one-rung problem.

ETA: I see he posted about "controlling the level". That's output. PID? straight start-stop? different rates of flow?

Imagine this: The Pump went on (started running), pumped out the water, then stopped.

What would have caused The Pump to start?

What would have kept The Pump running?

What would have stopped The Pump?

The pump output is implied;...

Click to expand...

I ask to be allowed to respectfully disagree. The Output should never be thought to be implied. It could be a Fan output, or a Heater output, or something else, or nothing. In which case the water would never get pumped. That tiny little first step is so unnoticable that it usually gets overlooked in the rush to a solution: Pump the water. It is the same method that a taekwondo senior uses to break a bunch of boards with his hand. He first visualizes that he has broken the boards. After that, it is a matter of applying the proper techniques.