Panel View Pushbutton Clarity?

ganutenator

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I don't currently have access to a PanelView for testing and am unsure about the button operations.

I didn't find the answers to these questions in my search of this site. Doesn't mean I didn't miss it though, if someone remembers a good link....?

Momentary
If I push a momentary button that is configured for normally open with a hold time of 500ms, I am assuming that the button will write a 1 to the PLC for 500ms and then write a zero. Does the zero get written for 500ms also? What happens if you lose comms during the 500ms in which the 1 is being written? Will it act as if an operator stuck a toothpick in a real life pushbutton to keep it latched.

Maintained
The way the wording in the help file is written, it looks as if the last value is stored in the PanelView. When the button is pushed, the panelview flips the state. Is this correct?

I notice that there is an initial state setting in the terminal setup dialog, the button configuration, and the tag configuration. Which one takes precedence on power up? What is the purpose of all three?

Can the PLC unlatch a Maintained pushbutton by unlatching the write tag, thus switching the button state?

Latched
Needs a Handshake tag to unlatch the pushbutton state.
The PlC must write a 1 to the handshake tag in order to change the state of the pushbutton back to state 0. How does this Handshake tag return to a zero? Does the PanelView reset it, or must the PLC reset it? What happens if the PLC resets the write tag?
 
Dude you are asking some Excellent questions.
The best thing is for you to get a hold of a micro and start messing with it.

I'm pretty sure that the momentary button will continue to write a 1 to the tag as long as you hold your finger on the button.

The PLC can unlatch a Maintained pushbutton by unlatching the write tag.

You'll have to check the help files to find out about the 500ms.
Good luck and enjoy!
 
Where's Ken when you need him?...

Yes, very good questions, and yes, it's hard without one sitting in front of you. It took me a while to find this in the help file, so perhaps you didn't dig DEEP enough in there?... :D

Using the 'index' tab within the help file, type "push button" and then click the indented "properties". They explain the handshaking pretty good there. Here's a bit of the text about 'initial states' and 'hold time'. I highlighted the answer to your precedence question... (y)

  • Initial State

    Specifies the initial state of maintained or multistate push button and the initial value sent to the write tag address. The value of the initial state overrides the initial value in the Tag Editor, if entered.

    Hold Time

    Specifies the length of time a momentary push button remains in the next state after being released. To ensure each state is read, the hold time must exceed the scan time of the controller. Hold time values are 0, 50, 250, 500, 750 or 1,000 milliseconds. The default is 500 milliseconds.
What I get from this is that the bit will turn on for AT LEAST that many ms. I agree with George that the bit stays on as long as the button is held. If you lose comms, the Panelview should complain that it can't write to the PLC... bawling

That's about all I can help with, as I don't have one 'handy' either... ;)

beerchug

-Eric
 
As I recall, the PanelViews that I worked with had a stuck button feature where the PV would fault if you held the button too long.
Or something like that.
The feature is selectable 0-60 sec., zero being disabled and 60sec being the max time a button(cell) can be held/stuck. Once the selected time has elapsed the PanelView will display a major fault screen with a "Stuck Button" message.
Zero is the default.

Too many aluminum cans. beerchug

Roger
 
Last edited:
Re: Where's Ken when you need him?...

Eric Nelson said:
Yes, very good questions, and yes, it's hard without one sitting in front of you. It took me a while to find this in the help file, so perhaps you didn't dig DEEP enough in there?... :D

Using the 'index' tab within the help file, type "push button" and then click the indented "properties". They explain the handshaking pretty good there. Here's a bit of the text about 'initial states' and 'hold time'. I highlighted the answer to your precedence question... (y)

  • Initial State

    Specifies the initial state of maintained or multistate push button and the initial value sent to the write tag address. The value of the initial state overrides the initial value in the Tag Editor, if entered.

    Hold Time

    Specifies the length of time a momentary push button remains in the next state after being released. To ensure each state is read, the hold time must exceed the scan time of the controller. Hold time values are 0, 50, 250, 500, 750 or 1,000 milliseconds. The default is 500 milliseconds.
What I get from this is that the bit will turn on for AT LEAST that many ms. I agree with George that the bit stays on as long as the button is held. If you lose comms, the Panelview should complain that it can't write to the PLC... bawling

That's about all I can help with, as I don't have one 'handy' either... ;)

beerchug

-Eric
 
Latched Push Button changes state when pressed and remains in the changed state until unlatched by the programmable controller.(The PLC must unlatch)

Maintained Push Button changes state when pressed and remains in the changed state when released. Pressing the push button a second time changes the button back to its original state.(This is a PanelView function, PLC can not change its state.)

Momentary Push Button (Normally Open or Closed) changes
state when pressed and changes back to its Initial State when released. (The hold time is so the PLC scan time doesn't miss the press, it does not work that way for the release, there is only a HOLD time not a RELEASE time. If communications is lost so is the "1", PLC inputs do not remain in their last state.

Startup state takes precedence.(safety)

I am only speaking of PanelViews such as the 1400e etc.
Roger
 
Last edited:
Maintained Push Button changes state when pressed...(This is a PanelView function, PLC can not change its state.)

You can change the state of a maintained pushbutton. Just write a zero or a 1 to the tag.

Type a unique name for the indicator tag. The address associated with this tag controls when the push button changes appearance with each state. If you define an indicator tag, an error state (ST E) is created on the States tab. The indicator tag is optional. Options are:

No Indicator Tag (default)
Push button changes to next state when pressed.

Indicator Tag same as Write Tag
Push button changes state after bit or value is written to the Write Tag address

Indicator Tag different from Write Tag
Push button changes state after bit or value is written to the Write Tag address and the state value is read from the Indicator Tag address.

Important: If the indicator tag and write tag are different, the indicator state is controlled by the remote device regardless of the push button state. For example, the indicator tag may specify that push button state 1 is displayed while the tag address is at state 0.
 
Thanks. I am on my way today to our distribitor. They are nice enough to let me test in their shop.

The panel view in question is a PV600 operating over DH485 to the serial port of a SLC 5/04.

My main concern is in the workings of the Latched pushbutton. Someone before me implemented 5 buttons on the panel view using the latched feature. They all use the same hand shake tag which the PLC is doing nothing with (no coil or output instruction even associated with its address). It works spuradically, and am suprised that it is even working at all. It must sometimes work because the plc resets the write tag every scan. Thus, the PV and PLC get into a fight as to its data value, but I am not sure.

Another implementation is a rung with a oneshot with no condition preceding the oneshot. This appears to work. The Panel View uses the momentary feature and writes to oneshot's address. I could expand on the explanation as I see it, but I got to get going. Basically the button, in conjuction with the oneshot, works when the button is released. thus working like a mouse up selection on an HMI. If the hold time is indead not used for the release, this could be a very bad implementation if there is a radio link or slow communication where by the PLC would miss the PanelView's write of a zero to the onesot's address.

More later, and thanks

I got to go, hope I didn't type this wrong, no time to review.
 
Type a unique name for the indicator tag. The address associated with this tag controls when the push button changes appearance with each state. If you define an indicator tag, an error state (ST E) is created on the States tab. The indicator tag is optional. Options are:

gbradley
What is your source of information?

Thanks
Roger
 
I coppied and pasted the Italicized lines from the Help files on Panelbuilder V3.70.00.

But I know from experience that you can change the state of a maintained push button with the SLC.
 
Thanks, I found the info but didn't have time to post. I guess I am out of date on a lot of things. I don't recall those options being on the versions that I used to use.
Time goes on.

Thanks again
Roger
 
If you are using a momentary PB and lose comms while pushing it, the bit will remain on until comms are restored and you press the PB again. I typically group all my momentary PB's in one address area and clear the range of addresses if I lose the Comm Active status bit for the Panelview in question.

Tom
 
just the facts

I spent a few hours testing with the Panel View at the Distributor, and this is what I found:

Momentary Button - [Normally Open, Single Bit, Write Tag, 1,000ms
hold time]

1) Holding down the Momentary button causes it to write a 1 as long as button is pushed. No error is ever reported for holding it down too long (My finger got tired after about 3 minutes).

2) The hold time is a minimum hold time and applies only to the writing of the 1. When the button is released, it appears to only write a 0 once.


recommended ladder for Momentary

write_tag do_something
--| |-------[ons]------( )



Latch Button - [Normally Open, Single Bit, Write Tag, Handshake Tag]

When Pushbutton is pressed, PanelView button goes from state 0 to state 1 and writes a 1 to the write tag.

PLC writes a 1 to the handshake tag.

PanelView sees this 1 for the handshake tag, changes the button back from state 1 to state 0, and then resets the write tag.

PLC sees this write tag as zero, then resets the handshake tag.

Note: this button will work sort of like a momentary button in this configuration.

recommended ladder:


write_tag do_stuff
---| |------------------|-------[ons]-----( )
|
| hand_shake
|-----------------( )




Note: Ensure that the oneshot is only in front of the do_stuff output, and not the hand_shake output.
 

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