PV 600 Color Touch Screen

I have a PV 600 color touch screen on one of our new machines and everything works fine but I have created a maintained button along with the rest of the program to switch the machine from manual to automatic. When I power up and run the machine and switch from manual to automatic for the first time it seems like I have to press the button twice on the PV and from then on it appears to work properly. (Just tap it with your finger)
Does anyone have an ideas on how to correct this?

Thanks,
Bob O.

PV Problem

The problem is the PV is in 1 state (manual) and the PLC is at another (auto) when you power up. This would only happen when the PLC is in auto and the PV defaults to it initial state (0). You need to set up the handshaking bits or the indicator tag to correct this problem.

The PV button initial state (0) and PLC auto bit initial state (0) at power-up. I can toggle the bit in the RSLogix 500 and the button switches as it should. I was told this is an issue with the PV at start-up. Just wondering if there is any there is any truth to this?

Thanks,
Bob

PanelView

Not sure if this is some issue with the PV. If it is, it is on a lot of them besides the 600. I had the same problem with a 1000. I had to have one tag for the write tag (EX: BurnerOn, B3:0/0) and another for the indicator (EX:BurnerOnInd, B3:0/1)

Mark,

I will try that when I get back to the shop and then give a follow-up after I test it.

Thanks,
Bob O.

Bob:

I don't have a PV in front of me to test, but I would look at the following:

In the tag editor, look at the initial state of each tag, and the update frequency.

On the button properties, I would look at the "Initial State", and the "Contact" type.

Good luck,

Marc

Marc,

I don't have it in front of me but I want to say I have the following:
initial state = 0
Maintained Button
Update Freq.= 1

I will double check when back at the shop.

Thanks,
Bob O.

Bob-
What interface ar eyou using (RIO, DH+, DeviceNet, etc). If it is one of the scheduled message interfaces (RIO, Devicenet, etc) the PV maintains an internal version of the information it writes to the plc. Also, I think the initial value field is only used on download. So I don't think you can assume that it will revert to the initial state on power-up.
I have always had bad luck with maintained functions in scheduled networks for just the reason you are referring to. If I have to use a scheduled network interface I usually stay away from maintained buttons. I use momentary buttons and do the latching in the plc.
If you need to use maintained buttons on the PV (for somethng like a state selector) don't do any conditioning in the plc. Use the bit directly from the PV. That will keep them synced up (as there is only one bit to look at). However, for something like a mode selection with a scheduled message interface I woul switch to momentary buttons.

Keith

This situation occurs with PV's on DH+ or DH485. These units only transmit to the PLC when the state of a button (or data entry field) is changed from the PV. It doesn't only occur at power-up.

If the last operation from the maintained PB on the PV was to set its bit 'on', then the next operation will tell the PLC to turn it 'off', regardless of the current state of the bit in the PLC - i.e. the bit may have been turned off by program. The PV remembers the last thing it wrote to the tag. For a 'toggle' operation like the maintained PB, it means pushing twice if the PLC has changed the state. Even more interesting on data entry - e.g. if you enter 100 in a field, then PLC program changes it to 200, you can't change it back to 100 from the PV unless you first enter some other value (200 even) because the PV essentially says "I've already sent 100 to that tag, give me something different to do".

The RIO PV's don't have this quirk (for better or worse). The devicenet PV's are similar to the RIO ones - at least for the 'IO slave' tags.

Bob

Yes the type of network connection is critical to how the P/B behaves at startup.

In essence messaging type networks (DH485, DH+, etc) only write data from the P/B to the processor on "change of data".

By contrast I/O type networks behave like a hard-wired P/B, ie. the data is read/written every I/O scan. In this situation the use of Maintained P/B's works well.

But for messaging type networks the usual solution is to set up the P/B as a "Momentary" type and use some extra logic in the PLC to set and reset a one shot toggle (Flipflop) to derive the action of a Maintained P/B.

There have been lots of threads about PB toggles elsewhere so I won't elaborate.