Proportional two analog outputs

[dark_jackal7]

Hi to everyone.

As a part of my project I have an analog input. I looked for FC105 and the control of analog signals. The quality of air is being measured. If the value is in range from 500ppm to 700ppm one analog output has to be opened 100%. When the value is between 700 and 900ppm both of them have to be opened 50% so their sum is 100%. When over 900ppm only the second one has to be opened. i dont know how to set up that proportion with those two outputs so any help is welcome.
Thanks in advance.

 

[L D[AR2P#0.0]]

If less than 500ppm then both analogue outputs are off ?

 

[dark_jackal7]

cant be less, there is no in the world that pure air.
if less only the first one is opened.

im using cpu 314ifm and step7 program.

 

[dchartier]

Hello jackal;
Look at the compare instructions (for LAD programming) in your program editor.
Use instructions that end in _R (for REAL value evaluation)as you are using the output of FC105 (a REAL value)for your program.
For example, in your first network:
use the CMP >R instruction with FC105-Output and 500.0
AND
use the CMP<=R instruction with FC105-Output and 700.0
If both are true then
Set your 1st analog output to max
Set your 2nd analog output to min

Do the same (with the correct compare instructions and values) for the next two distint operations.
Hope this helps,
Daniel Chartier

 

[L D[AR2P#0.0]]

..

 

[dark_jackal7]

thanks both of you, I ll try this.

 

[dark_jackal7]

solution is working. the problem is that in plcsim, where I put the slider of piw256 on input and Q127 as output, when I move the slider it doesnt switch to the another output on the values of ppm I put in the comparators.

any suggestions?

 

[L D[AR2P#0.0]]

If the solution is working then the problem your are referring to is to do with monitoring the program - correct ?

 

[dark_jackal7]

yes, the problem is with plcsim. the piw input is going over the high limit set into the scaling function fc105.

 

[robo77]

and class has ended too soon..lol

 

[dark_jackal7]

I have some more problems with some other part of code. I have the analog input of temperature with limit between 18 and 30 degrees of celsius. So I put the fc105 with those limits and output of the scaling function to MDxx. My output is threeway valve which is 0..10V.
How can I assign 18 degrees to be 100% valve opened(10V)and 30 degrees 0% valve opened (0V)?

I dont have the margins so I cant put 24 degrees is opened 50% and 28 degrees opened for 20%. What I need that as the temperature rises the valve is closing down.

 

[cagliostro]

Hi,

use the FC106 as the picture below attach

Regards
http://img215.imageshack.us/img215/4205/fc106.png

 

[dark_jackal7]

this is what I did. im missing something..

 

[L D[AR2P#0.0]]

I dont have the margins so I cant put 24 degrees is opened 50% and 28 degrees opened for 20%

Yet this is exactly what you are now trying to do

 

[cagliostro]

Hi,

if you reached the purpose as the image attached in your last post, I think you solve the problem!!!

I think you don't have missing nothing, every thing correct.....you're moving in the right way.