aikorob

PV9 pushbutton changes state automatically

9 posts in this topic

We have an old 9" PanelView screen, connected to a SLC5/03 processor. 2711-T9C3     PanelView controls a blender. This system has been in place since 1997  with no problem until the past few months.

At the end of the batch, operators must toggle a PushButton on the screen--from AUTOMATIC to MANUAL.

Change of state  is indicated by a back ground color change.

Operators then toggle a VALVE OPEN PushButton, again indicated by background color changes.

Both of these are Maintained PushButtons.

Problem in the past few weeks is that the VALVE OPEN button has been toggling on its own---with no operator touch---the screen shows the change of state of the bit. When this happens, the valve closes automatically, and the operators can simply go back and touch the screen 1 time to open the valve. Problem is very intermittent. Problem DOES NOT happen between batches when operators are cleaning blender. Blender is used for plastic powders, so static can be a problem at times--screen. PLC, and all panels are grounded. I thought perhaps that particular area of the screen was developing problems, so I moved the button to another location---has not helped the problem.

Any suggestions?

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You could add timers to the button change logic so that the PV tag must be ON (or OFF) for time before you latch the output condition.

This is a good way to making sure an operator doesn't accidentally actuate a motion by simply touching the screen.

On a related note, your PV900 may be showing signs of premature failure.  You do have a spare unit?

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I would investigate the PLC operation before blaming the display. Look for any possible way the state can be changed in the program without a signal from the display.

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Operators are 10' away from screen---watching product being unloaded into hopper. When product reaches a certain fill level, they walk back to screen and push button to close valve. Only 1 operator in this area---unless they are The Flash, operators are not accidentally pressing touchscreen.

System in place since 1997--premature failure may be a possibility.

 

PLC program rung has 2 NO push button----Automatic/manual   & valve open/closed    OTE for valve to actuate

Automatic/manual NEVER shows change of state on screen when problem occurs---Valve open/close push button shows change of state

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Post a screenshot of the code.  You can easily add event counters to track IF a function is being intermittently triggered.  I am with b_carlton...I would suspect the PLC program.  Yes, it has been in operation since 1997, but there could be an underlying culprit allowing this event to occur that is a function of the PLC code.

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Look for a quick 'off blip' on the emergency stop - I:1/0 - input. That would reset the HMI pushbutton bit. I don't know what else it would cause. Install a counter in parallel with the rung 63 unlatch of the bit. See if it increments unexpectedly.

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Bernie, I've had exactly that sort of thing happen.   It was a loose wire on the aux contact on the e-stop, so the emergency stop loop didn't drop out but the related logic that depended on its status would unexpectedly reset.

That got me in the habit of adding a latched alarm rung for e-stop cycles.   Knowing when the e-stop circuit was used has all sorts of benefits, including knowing if the operators are using it inappropriately.

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talking to 3rd shift maintenance this morning---asked if they had any recent problems---"no problems, but we had to change an E-STOP button out last week"

I took a look at it--we use 30m Square D  9001KR9P1 maintained push-pull. This particular button did not "snap" open or closed; it felt mushy and soft.

maybe this will solve the problem. If any further problems, I will add the counter as b_carlton suggested

thanks for your suggestions

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