• Replies 6 replies
  • Subscribers 1 subscriber
  • Views 19 views
  • Users 0 members are here
Options
Related

NO Momentary pushbutton stays high

Admin
I have some NO momentary push buttons in my application that will set the tag high but wont reset the tag low after the button is release.
On the command line for the button the tag is set while down and reset while up. Normally the push button works fine, but the odd time, maybe once every two weeks, the tag in the PLC remains high. The tag is only referenced in the HMI so I know there isnt anything in the PLC latching it. The PLC is TwinCat and I am using 7.1 for Indusoft. Any ideas?
Parents
  • The problem with momentaries in a HMI is that you cant guarantee that the PLC will see it within the time frame.

    The following methodology gives you momentary like functionality and also includes an implied acknowledgement

    Use a set command in indusoft to set the bit high and in the PLC use a reset coil to set it low after it has been acted on, which in turn will set it low in the HMI.

    the implied acknowledgement works like this,

    if the HMI has set the bit and it remains high for too long then the PLC has probably not received and reset it so you probably have a comm error
Reply
  • The problem with momentaries in a HMI is that you cant guarantee that the PLC will see it within the time frame.

    The following methodology gives you momentary like functionality and also includes an implied acknowledgement

    Use a set command in indusoft to set the bit high and in the PLC use a reset coil to set it low after it has been acted on, which in turn will set it low in the HMI.

    the implied acknowledgement works like this,

    if the HMI has set the bit and it remains high for too long then the PLC has probably not received and reset it so you probably have a comm error
Children
No Data