Examine Off Bit

Hey
I have another crazy question regarding the "Examine Off" bit?

I have a situation to were if I toggle a "Examine Off" bit it will shut down a process. So if the bit goes true it shuts down.

Now this may not be the best way to do this but its what I have currently.

Some questions I have are:
1. If i configure Wonderware button as a "Toggle" action on the Examine Off bit the process goes down.

This is OK and all good....Now

2. I have been struggling with the PLC code to wite this to were the bit holds in the "True" or "1" state until a reset is pressed to put it back into the "off" state.
3. Once back into the off state, then the unit is cleared to restart.


Can this be done with what I have here to work with?
If so can you guys instruct me on the correct PLC logix to accomplish this?


thanks,

Ones_Zeros said:

Hey
I have another crazy question regarding the "Examine Off" bit?

I have a situation to were if I toggle a "Examine Off" bit it will shut down a process. So if the bit goes true it shuts down.

Now this may not be the best way to do this but its what I have currently.

Some questions I have are:
1. If i configure Wonderware button as a "Toggle" action on the Examine Off bit the process goes down.

This is OK and all good....Now

2. I have been struggling with the PLC code to wite this to were the bit holds in the "True" or "1" state until a reset is pressed to put it back into the "off" state.
3. Once back into the off state, then the unit is cleared to restart.


Can this be done with what I have here to work with?
If so can you guys instruct me on the correct PLC logix to accomplish this?


thanks,

Click to expand...

Providing that the process will require another button to restart, then the "Examine Off" XIO controlled by (presumably) a STOP button on the HMI only needs to be a "Momentary" type button. In other words it writes the XIO bit back to 0 (XIO = True) when released.

This type of control is very common, see the picture.

The START button turns on the ENABLED bit (because the STOP button is true), and on the next PLC scan the ENABLED input bit "Seals In" the ENABLED output.

A "momentary" false of the STOP bit "breaks the seal", and the ENABLED bit goes false. After the STOP button is released, it will require another press of the START button to make it go again.

NOTE : If this were a hard-wired control, then the STOP button would typically be a N/C button, so the XIO STOP would need to be an XIC STOP. This is done for a degree of safety, so that if the wire drops off the STOP button, the seal-in is broken, otherwise there would be no way to stop the process.

NB : This is never to be used for an EMERGENCY STOP, those must always be external to the PLC.

Thanks Daba,
Basically this Shutdown is just a Remote Wonderware
Shutdown.

I’m just toggling the ww_shutdown bit, which
Currently normal is false, I pick it up & make it true
To shutdown the process.

I was just wanting another way to latch/unlatch the bit,if that’s
The best way, to keep the bit true & Shutdown
Until a reset is pressed.

I know I could just toggle/Un-toggle the bit,
But if the ww_shutdown bit has been toggled
& is now true, is there any Logix to keep
It true until a different reset bit is toggled
Giving a permissive to start?


Thanks

Ones_Zeros said:

Thanks Daba,
Basically this Shutdown is just a Remote Wonderware
Shutdown.

I’m just toggling the ww_shutdown bit, which
Currently normal is false, I pick it up & make it true
To shutdown the process.

I was just wanting another way to latch/unlatch the bit,if that’s
The best way, to keep the bit true & Shutdown
Until a reset is pressed.

I know I could just toggle/Un-toggle the bit,
But if the ww_shutdown bit has been toggled
& is now true, is there any Logix to keep
It true until a different reset bit is toggled
Giving a permissive to start?


Thanks

Click to expand...

The enable logic that daba posted will do what you want, and you won't need to use a toggle pushbutton in InTouch. Simply make both the "Disable" and "Enable" pushbuttons momentary pushbuttons.