Pump feedback

manin · Mar 25, 2018

Hello, I have a problem I can't solve so far.

I have read a few other posts but I did not find understood, something about my problem.

I have a pump that works in automatic mode. If pump is enabled after 2 seconds a feedback must enable an input at plc. If not must set the alarm and stop the pump.

The alarm must be cleared if pump and feedback are both enabled or disabled.

At this point, if pump does not return feedack, it stack into a loop, alarm and clear alarm..

I use Fatek plc.

Best regards

nhatsen · Mar 25, 2018

If the pump is really starting, you may have a blown fuse in the feedback input.

tarik1978 · Mar 26, 2018

Use the schematic and your multimeter to check for voltage at feedback starting from input side and going back until you find the culpirt it could be a loose wire bad contact blown fuse...

manin · Mar 26, 2018

nhatsen said:
If the pump is really starting, you may have a blown fuse in the feedback input.

I am looking for a ladder way to do it...
I can't to add anything else

tarik1978 said:
Use the schematic and your multimeter to check for voltage at feedback starting from input side and going back until you find the culpirt it could be a loose wire bad contact blown fuse...

There is not any electrical issue. The way it is asked, it is going in a loop...
I am just trying to find something, that will solve my problem without changing the result

Thank you both for your time

Aardwizz · Mar 26, 2018

Your problem is that you are energizing the output, and then when the feedback doesn't match the output, you alarm and thus stop the motor,turning off the output. Now the feedback DOES match the output, so there's no alarm condition, which allows you to turn on the output, ad infinitum.

You have the rule:

manin said:
The alarm must be cleared if pump and feedback are both enabled or disabled.

but you aren't clearing the alarm -- that is, requiring a human to say that the pump has been looked at and is OK to be tried again.

You need to have some sort of Reset button, or Alarm Acknowledge system on your HMI or user interface. I knew one company that, rather than having yet another input, used the HOA switch (which was wired to the PLC) to ensure that the motor had gone to OFF mode, then back into Hand or Auto before the motor could be tried again.

With whatever Reset strategy you decide to use, you'll then latch the Alarm bit, and use the Reset to break the latch. Then your motor code will work as you intend.

manin · Mar 28, 2018

Aardwizz said:
Your problem is that you are energizing the output, and then when the feedback doesn't match the output, you alarm and thus stop the motor,turning off the output. Now the feedback DOES match the output, so there's no alarm condition, which allows you to turn on the output, ad infinitum.

You have the rule:
but you aren't clearing the alarm -- that is, requiring a human to say that the pump has been looked at and is OK to be tried again.

You need to have some sort of Reset button, or Alarm Acknowledge system on your HMI or user interface. I knew one company that, rather than having yet another input, used the HOA switch (which was wired to the PLC) to ensure that the motor had gone to OFF mode, then back into Hand or Auto before the motor could be tried again.

With whatever Reset strategy you decide to use, you'll then latch the Alarm bit, and use the Reset to break the latch. Then your motor code will work as you intend.

Thank you!
I did it this way

Pump feedback

manin

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nhatsen

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tarik1978

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manin

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Aardwizz

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manin

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