Michael Lloyd

PIDE Question / Problem

3 posts in this topic

I'm having trouble with 4 identical PIDE's. I needed them to go to manual and 0% on a discrete event. I built a little 1 rung solution that latches a bit for one second that puts the controller in manual and moves 0 to the CVOper value for the loop. The latch is reset on timer done. It works great except there's one little problem, it's always writing a 0 to the manual select bit so when an operator, using an HMI connected to the server via cell modem, tries to put the controller in manual, nothing happens. Since I can break the wire (I made an AOI and used function block) to the manual request and save the block to make it work I'm pretty sure the problem is there. 

Every now and then I need to do a bit toggle like this and I run into the same problem. It toggles fine but thanks to the long lag time between the HMI the 0 that is being written to the tag overrides the 1 that the HMI send.

Thoughts?

 

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Is the main issue that, the PLC writes a 0 and the HMI writes a 1 to the same tag?

Can you add some animation to the HMI to make the HMI controls invisible when you want the tag to get the value from the PLC only?

Or add a button to the HMI that the operator presses to indicate they are going to operate the PIDE manually. Then only read the tag value from HMI when this button is pressed.

 

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I guess the cell served HMI would need the contact to be latched for a period of time? I think that's the problem? Just want to make sure I don't plant foot in mouth...

John

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