HMI press and release button events

[grnick50]

Hello all, considering good programming practices how do you handle press and release button events in HMIs.
I have seen people using the release event in favour of the press event. What is the reason for that?
i have seen people having momentary button function in HMIs using the press event to set a bit in the PLC and the release event to reset a bit in the PLC. On the other hand I ve seen people seting a bit with the release event in the HMI and resetting that bit in the PLC code right after it is used in the code (they consider it safer).

Personally I ve used most of the methods but as we are trying to set company standards, I am trying to find the best method.

Regards

 

[Aabeck]

The main reason for release event is that if you press a button in error and slide off it to another button and release the second button, the PLC would not know you pressed the first button. I am not sure if this is true for all HMI's, but it does work on many.

 

[Aabeck]

And for the momentary vs maintained, The benefit I could see is if the comm's are lost while the bit is on then the PLC would not know it is released.

Personally I use momentary PB's, check for a OSR or ONS, then turn the bit off by a AFI OTE [PB]. If the operator is still holding it PB ON the scan will turn on the bit and not trigger the OSR again - also during testing I can toggle the bit while online with the PLC and after the PSR it turns off, so I can test the HMI operation without the HMI.

 

[ASF]

I don't like using press and release because if the comms drops out between when you press the button and when you release the button, your button function gets "stuck".

Personally I use the release because it's similar to the way most people are familiar with Windows buttons working...if I press and hold the "post reply" button below, it won't actually click until I release it, and I can drag off it without activating the release if I meant to click a different button