Stopping at an analog height value

Hi All,

I'm struggling with a bit of logic and am wondering whether you excellent bunch can help or point me in the right direction ......

Basically i'm using push buttons to manually raise & lower part of a machine. I get an analog value back giving me something I can use for height feedback.

I need to stop the machine at a particular height value (which i can do) but then if i press the button again, i need to allow the machine to continue moving in that same direction.

I don't want to just use an "if height = 3000" (for example) to stop as the feedback from the sensor might miss that particular value and not stop, so instead I am using an "if height > 3000" which guarantees it will stop but this gives me the problem of how to ignore this when the push button is pressed again after the machine stops.

I hope i've explained that okay, all help will be greatly received, thank you

Mark

Pressing the button should energize a one shot which latches a bit indicating travel. The bit will allow the rungs which control movement. Unlatch the bit when the target is reached. If the button is held for the entire movement then releasing it could unlatch the bit if it is released before the target is reached. Otherwise make sure to have a stop button.

Here's a version in Siemens TIA

L D[AR2 said:

Here's a version in Siemens TIA

Click to expand...

Thank you, looks perfect. I'll have to do the same for the lower direction so it stops at the threshold on the way down too, but i can work that out now