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solomoneli

Can't turn on a pump using multiple inputs

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I'm writing a pretty basic couple of nets, and I can't get a pump to turn on in a certain instance.  It turns on in net 2, but not Net 1.

 

Can somone please explain what I'm doing wrong?  And how I can fix it?  

pump not turning on.JPG

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Direct coils should be used in one, and only one, place in your program. In your case, you are turning it on in net 1 then turning it off again in net 2. The state doesn't get written to the physical output until after it's turned off in net 2. We have a saying with ladder logic - "the last one wins".

Figure out all the conditions you need to turn the coil on and write them into a single net.

The exception to this is Set & Reset coils activated by a transition contact. You can have those in multiple places if you choose.

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Flex speaks truth.  In addition-

You've made good use of positive transitionals to help keep your logic from getting stuck.

Each net is considered one logical statement in UnitronicsLand.  Each of your nets has three statements - don't do that.  Separate timer contacts from their coils, too.

image.thumb.png.04271d735fb93afdc47acc9239bcee1c.png

I realize this looks inefficient compared to your logic, but if you look at the compiled logic  - STL Quick View - of what you've written you'll see it's rather messy.  Extra nets have zero memory cost when the logic is compiled.

Joe T.

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