How to use same output on different networks?

[JAM007]

I have designed a program for an S7-1214 so that when you activate input .1, it will output a certain set of commands to make a robotic arm pick up a puck, rotate clock wise, drop the puck, then return to its original location. I created this program on network 1. When I tried to design a similar program that uses a different input (.3) on network 2 to make the arm go counter-clockwise, nothing is output. Both of the networks share the same outputs, but I don't understand why the program works when input .1 is activated, but not when input .3 is activated. Any suggestions?

 

[Nelliyan]

U cant use Q flags in more than 1 networks.

If u want that to happen then use M flag bit in ur logic whereever u want to switch that op & finally map that M bit to Q flag( Op).

Regards,
Nelliyan.G

 

[Espiration]

Don't forget that the PLC runs in cycles. So if you have 2 networks with the same Q, it will only output the state of the last Q you've entered (last network you used it in). The PLC won't give any problems if you use a Q more than once but it just won't work like you want to.

 

[JAM007]

U cant use Q flags in more than 1 networks.

If u want that to happen then use M flag bit in ur logic whereever u want to switch that op & finally map that M bit to Q flag( Op).

Regards,
Nelliyan.G

I am implementing M flag bits into the logic, but am still getting the same problem.

Don't forget that the PLC runs in cycles. So if you have 2 networks with the same Q, it will only output the state of the last Q you've entered (last network you used it in). The PLC won't give any problems if you use a Q more than once but it just won't work like you want to.

So the only way to achieve what I want to do would be to use a second S7-1214, since there aren't enough outputs on one?

 

[rQx]

Go online and see what happens?

Or share the program (print screen?) so we can see what you have done?

 

[Espiration]

See it like this

[ladder]
NW1: 
I0.0   Q0.0
--||---( )--
 
 
NW2:
Q0.0   Q0.1
--||---( )--
 
 
NW3:
I0.1   Q0.0
--||---( )--
[/ladder]

Follow with me for a moment:

1. PLC reads inputs and sees that I0.1 = 1 and I0.1 = 0

2. PLC starts cycling in the code: in ONE cycle it will do this:

NW1: I0.0=1 so Q0.0 will be set to 1

NW2: Q0.0=1 so Q0.1=1

NW3: I0.1=0 so Q0.0= will be set to 0

3. PLC will set Q0.0 to 0 and Q0.1 to 1


So even though the outcome of Q0.0 is 0, Q0.1 will be 1. This only counts CYCLE PER CYCLE. Why is this? Because the networks before won't be bothered by changes in the code after it for that particular cycle.

Hope I helped you a bit, it's a hard theory but interesting nevertheless. What I just told you is the reason you can't use 2 of the same outputs.

 

[JesperMP]

You should have something like this:

                            Case_A
|---(conditions)-------------( )

                            Case_B
|---(conditions)-------------( )

   Case_A                   output
|---| |----------------------( )
|          |
|  Case_B  |
|---| |----x

 

[JAM007]

So even though the outcome of Q0.0 is 0, Q0.1 will be 1. This only counts CYCLE PER CYCLE. Why is this? Because the networks before won't be bothered by changes in the code after it for that particular cycle.

Hope I helped you a bit, it's a hard theory but interesting nevertheless. What I just told you is the reason you can't use 2 of the same outputs.

Thank you, this helped me to understand the networks better. It was stuck in my mind before that each network worked individually.

You should have something like this:

                            Case_A
|---(conditions)-------------( )

                            Case_B
|---(conditions)-------------( )

   Case_A                   output
|---| |----------------------( )
|          |
|  Case_B  |
|---| |----x

I changed my code around to follow this design, and it worked flawlessly. Thank you so much for this, I greatly appreciate it.