ZelioSoft: output normally closed

Does anyone know how to get an output to be closed when rebooting the zelio (for example: after a power failure)? I could try playing with complex logic, but there must be a simple way to do something on "boot" and have it trigger a pulse for example.

I connected a "1" (always on) to a "pulse on edges", but that doesn't work, and it actually makes sense too.

I can't find a setting to change the default behaviour of an output, and I can't find any logic block that pulses or rises when starting the PLC.

Help

Pulse on Edges would need to see a change in the logic from 1 to 0 or 0 to 1 depending, not to mention by the title of the instruction it would just pulse once not stay on.

If you want an output to be closed when the PLC is booted just put your

"Always ON" instruction > XOR > then Output

You can use the XOR to make the output false at some point in your program if need be.

I have not uses Zelio but a hand full of times and mostly use Logo for small controllers like this.

Are you using ladder or function blocks to program with?

My example is using function block but if you are using ladder you can do the same thing by adding a ]/[ instruction between the Always On and your output
This way you can condition the output to be false when needed.

BCS

Thanks, I'm using ladder. However, I don't understand how using a XOR would accomplish this. I have some logic making the output both 1 and 0 (by setting, unsetting, toggling, ...). I would just an initial set.

I stumbled upon SFC which has some init-functionality, I think that might work.

No matter what you do in logic I do not believe the output will turn on until the second scan - the first scan is a check scan normally but do not know a lot about a Zelio.

Wire a relay to the output, and use the normally closed contacts of the relay to whichever device you need to be "normally energised"

marnik said:

Thanks, I'm using ladder. However, I don't understand how using a XOR would accomplish this. I have some logic making the output both 1 and 0 (by setting, unsetting, toggling, ...). I would just an initial set.

I stumbled upon SFC which has some init-functionality, I think that might work.

Click to expand...

I may have mis-interpreted what you were looking to do.
I thought you wanted the relay to be close when the PLC boots back up.

Now it seems that you want the relay to be closed while the plc is powered down.....if that is the case then ASF's suggestion would be the way to go if you are just wanting the field device to be energized during PLC off state.
But if you are looking for the actual output to be true in the logic to get an initial "Set" as you say then this will not work either.

If you can post a screen shot of what you are trying to do or give better explanation of it, that would help get you the best answer.

BCS

A lot of "IF's here but....

If you are just looking to initially "SET" an output upon PLC Boot, then the picture below should do that.

The top of rung #1 is your existing logic (what ever it may be). You said you are setting and resetting so I am assuming you are using a "SET" output instruction.

The parallel rungs are the logic that you would need to add for an initial set of your output.
Note: The output I added is also to be a "SET" type output instruction.

The always on instruction will set both bits on 2nd scan (as BobB pointed out).
The Always On instruction will then be conditionally blocked by the "SET" output I added on the parallel rung.

Rung #2 would be your existing logic for "RESTING" your "SET" output.

The "SET" output I added on the parallel rung will not be reset until the PLC is switched from an off to an on state again. (See disclaimer below)

2 more BIG IF's....

Zelio needs to allow you to parallel rungs (I forget if it does or not)

Zelio "SET" instructions can not be retentive (they must be false (0) upon boot of the PLC for this to work right.

If this is what you are looking for and the answer is yes to the 2 big if's then this should work.

If this is still somewhere out in left feild and not what you are trying to do then please provide more detail.
Reading your post I think this is what you are trying to do now.

BCS

And here is what I was suggesting in my first comment about using an XOR.

The output would be true upon boot.

You would then control your output inversely by adding any additional true logic to the XOR to make your output false.

All just WAG's as to what you are actually trying to achieve and how you are trying to achieve it, since we cant see what you are actually trying to do.

Good luck,

BCS

If you find that the "SET" instructions in Zelio are retentive, then this would be another way for you to get there.

At least I am 99% sure you can get there from here, I am pretty sure you will get one scan with the C4 instruction not true so your "SET" output would initially set for you.

(If I am wrong about that we will know in ....3...2....1 )

OR....And I can't believe I overlooked this one.

If Zelio has a "First Scan" instruction....just put that on a parallel rung to your set and you are done.




BCS

Hello Marnik,

I dont know if it is what you want, and if Zelio supports it, but what I understand with your question is that you want an output to become, or stayed high when rebooting the PLC.
A lot of PLC's have the possibility to setup the behavior of an output when the PLC stops or reboots. ( always off, always on or hold last state)
When your system supports that you can setup the output to become always on, and set it to off when the PLC starts running the code.

greetings
John.