How does wrt.not work in fanuc plc programming?

alive15 · Jan 22, 2021

Good afternoon all, hope everyone is doing well. Could someone explain the pic attached on the wrt.not instruction? To me, it looks the same as the regular wrt instruction. I really don't understand it's purpose at the moment, and looking to get some clarification on how it works?

I thought it would prevent the output from coming on, but looking at the status of operation result on the right side confuses me, as it gives the same status as the regular wrt instruction.

Thanks!

Steve Bailey · Jan 22, 2021

I've always had problems understanding what Fanuc manuals are trying to tell me.

My interpretation of of the example logic is that the state of Y14.6 will be the opposite of Y11.1

alive15 · Jan 22, 2021

Right, so if all input conditions are met, I would think y11.1 would be = 1, and y14.6 = 0.

So I don't get the purpose of setting the output = 0, because I could just add more input conditions to prevent it from happening?
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Ahh, actually now I get it, the output would be on if the input condition is false, and it's off if all input conditions are true.

Has anyone ever used that logic for any particular application? To me, it feels like the wrt.not makes the output a normally closed signal, but wouldn't it be easier to have normally open output and just change inputs to be n.o or n.c.?

It's very interesting now that I understand it, but I don't see any particular scenario where wrt.not would be preferred over wrt. It's almost like a preference choice, not an engineering / design choice?

Bit_Bucket_07 · Jan 22, 2021

alive15 said:
Right, so if all input conditions are met, I would think y11.1 would be = 1, and y14.6 = 0.

So I don't get the purpose of setting the output = 0, because I could just add more input conditions to prevent it from happening?
-----
Ahh, actually now I get it, the output would be on if the input condition is false, and it's off if all input conditions are true.

Has anyone ever used that logic for any particular application? To me, it feels like the wrt.not makes the output a normally closed signal, but wouldn't it be easier to have normally open output and just change inputs to be n.o or n.c.?

It's very interesting now that I understand it, but I don't see any particular scenario where wrt.not would be preferred over wrt. It's almost like a preference choice, not an engineering / design choice?

Yes, it's just a negated output, and it's not necessary, but available if you want it.

Steve Bailey · Jan 22, 2021

I once found a practical use for the negated coil instruction.

Back before the GE Fanuc 90-30 added an off delay timer to the instruction set I could create one using a standard timer with a one-shot triggering the timer block and a negated coil as the output of the timer. Firing the one-shot turned the negated coil on and it stayed on until the timer timed out.

Then they added the off delay timer at a later firmware version....

alive15 · Jan 25, 2021

Yeah, I see what you are talking about. Thanks for the info guys, have a great week~

NetNathan · Jan 25, 2021

I use negated coils to control NO valves.

How does wrt.not work in fanuc plc programming?

alive15

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