Momentary Pushbutton With Maintain Functionality

[BrandonLewis]

I am trying to implement a momentary pushbutton for a customer where we have the button maintain the command (send digital value 1) for 5 seconds without having to hold the button down for the duration, and then after the delay, (send digital value 0). We have a number of customers now that are requiring this type of functionality with their HMI due to setup of the end device and equipment. A work around right now is to implement some form of logic program to do this but it would be simpler to just have this available in the button's pick action settings.

[BevanWeiss]

This isn't a good idea.  If the SCADA server loses comms to the PLC, then you will end up with a value that is still left 'ON'.

Your best idea would be to modify the PLC code to turn off / reset the flag once it has performed the action.

The only situation where momentary buttons should really be used is for things like jogging controls, and I'd very much recommend this to be performed using a hard-wired control rather than a SCADA / HMI control.

Doing it with logic allows for the Client and Server to be kept separate, and reduces the possibility of assumptions being incorrect for a given application.

i.e. in your example, if you have the button configured for 5 seconds.. and user 1 pushes it every 10 seconds, and user 2 pushes it every 10 seconds (but offset by 5 seconds from user 1)... what should the state of the tag be?  should it always be '1'? or should it ignore the second user? or should it ignore the first user on their second press? 

[sbeadle]

Thank you