How to calculate the decimal value of thumbwheel bool input?

[wqtony2004]

hi, guys. I am using the Siemens setp 7. I have a thumbwheel input in the panel, which has four bit input all boolean ones? How can I get the decimal value of this wheel input, thanks a lot! PLZ help me- a new leaner of PLC.

 

[wqtony2004]

FYI, I am programming using the ladder diagram.

 

[wqtony2004]

I am working under S7-300, the device is CPU 314C-2 PN/DP

 

[Bullzi]

I would take a look at http://www.plctalk.net/qanda/showthread.php?postid=23381#post23381 for a good explanation.

 

[wqtony2004]

I would take a look at http://www.plctalk.net/qanda/showthread.php?postid=23381#post23381 for a good explanation.

Thank you first, i have already read this thread, but i am a new leaner I still can not quite follow Ron Beaufort's meaning.When i check the input i found that my thumbwheel has 4 boolean input with their address fixed in I137.3,I137.2,I137.1,I137.0 repectively. The situation sames different mentioned in the thread you offered, coz they are dealing with binary input,though the value is same but the format of value is different, right?
So, is there any way i can access my thumbwheel input and get a decimal value?

 

[L D[AR2P#0.0]]

Assuming the thumbwheel inputs are coded in BCD and produce 0-9, here's one implementation:

 

[L D[AR2P#0.0]]

.. or another..

 

[wqtony2004]

.. or another..

First, thanks for your help ,LD.
I still have some questions.
In the first figure you offer, is there any possible the initial instruction will be implemented after other bit instruction? If not, is it because the program scan is top down, so it will always implement the top instruction first?

In the second figure, do you mean we use a word 'AND' instruction between 4 bit thumbwheel input and 'FF', and then we get the decimal output? what if there are some random '1' in the high bit of word I137?

 

[L D[AR2P#0.0]]

In the first figure you offer, is there any possible the initial instruction will be implemented after other bit instruction? If not, is it because the program scan is top down, so it will always implement the top instruction first?

No and yes.

 

[L D[AR2P#0.0]]

In the second figure, do you mean we use a word 'AND' instruction between 4 bit thumbwheel input and 'FF', and then we get the decimal output? what if there are some random '1' in the high bit of word I137?

The AND is with F, not FF so the high bits of byte IB137 are masked to zero.

 

[wqtony2004]

The AND is with F, not FF so the high bits of byte IB137 are masked to zero.

In the fig2, the data type of 'move' is different, can it be implemented?

 

[shooter]

or use the simple ladders 10 of them
not 0 AND not1 .... coil=0
0 AND not1 ... coil=1
not0 AND 1 .... coil=2
....

 

[boneless]

Why is the data type different in fig. 2?

 

[L D[AR2P#0.0]]

I think the OP is referring to the fact that I am moving a byte to a word. The screen shot is from my Step 7 program so yes it can be implemented.

 

[wqtony2004]

Why is the data type different in fig. 2?

I mean in fig.2 the bottom right 'move', the input is byte while the output is int, will it work?