Basic PLC Question

[pLcJohnGuy]

What ladder logic is required to have an HMI button that gives output when you push it then removes that output when you push it again? For example, in the attached picture, I push the button in a seal branch and it turns on the output... The idea behind it is a String that goes to output when I push the button then removes from output when I push the button again. Any suggestions?

 

[dmargineau]

... The idea behind it is a String that goes to output when I push the button then removes from output when I push the button again.

Welcome to the Forum!

?!...the are no Strings in Bit/Boolean logic...

It is called Flip/Flop logic...

 

[Mickey]

Other methods...

 

[geniusintraining]

Other methods...

Nice! never saw that one before

 

[Gomez_]

Here's an interesting one I've been using:

You can adjust the times as needed, something around 50ms would act like a normal button press, or in my application they need to hold the button down before the machine moves.

 

[T Gibbs]

Easiest way is to use a toggle button on the HMI.

 

[OkiePC]

Welcome to the Forum!

?!...the are no Strings in Bit/Boolean logic...

It is called Flip/Flop logic...

The logic in that image won't actually work... You need another storage bit in parallel with the OTL to inhibit it from unlatching on the very next branch.

 

[OkiePC]

There...

 

[danno4200]

I myself prefer a seal-in version, like the one in this image, over the latched / unlatched

 

[godcixelsyd]

Easiest way is to use a toggle button on the HMI.

I was taught to not use most of the fancy buttons in the HMI (toggle, latch, etc.) because if someone is reading the logic and isn't familiar with how the HMI was done it can be confusing to them. I guess in the bigger world it's programmer preference, and customer demand.