Maximum power transfer

[Jay.kothari]

Hi

   I am using Labview 10 and would want to implement Maximum Power Transfer Theorem. I have attached a VI which calculates the maximum power. Now I want a way in which I can plot the graph of Power v/s Rload/Rsource.
The attached method does not work. Please help me on the same

Jay

[johnsold]

Jay,

You only have one data point so how do you expect to plot anything?  If you want to scan over a range of values for the source or load resistance you need to have a loop and inputs for minumum and maximum values.

To do something like that I would recommend moving away from the resistor color code to simple numeric values for resistance.

To work with the color codes I recommend switching from string inputs where any typing or spelling errors lead to problems to enumerated controls which can only have the designated colors.  I would also create a subVI to compare the colors entered to the standard resistor values.

Lynn

[Jay.kothari]

johnsold

I tried putting a while loop and tried using a stop button but it aint helping me. I want run the loop for values of  Rload and Rsourc above and below the valeus when they are equal and then plot a graph. Can you help me in doing so ?

Jay

[johnsold · Accepted solution]

Jay,

From your other posts I think you need to do two things:

1. Learn more about LV.  These kinds of simple loop programs are very basic.  If you do not understand this stuff, you have no chance of reaching your goals.

2. You need to define exactly what you want your lab exercises to do.  Are they to be purely software simulations or will you have real voltages, currents, temperatures, and so on, to measure?  If it is to be all software, then you need to select all the models and define all the equations and algorithms for those models.  If you will be making measurements of real physical quantities, then you need to define what you will be measuring and the range of allowable values for each parameter.

After you have those definitions, then you can begin to design your system.  Select measurement hardware.  Select software architectures. Design program structures.  Adapt algorithms, if necessary, to LV's dataflow paradigm.  Then start writing VIs.

Here is a simple looping VI for your power calculation.  Note that your model is not the same as a photocell so the curve is different.

Also note that people on this Forum are mostly volunteers.  We are glad to help you learn to use LV, but we will not do your work for you and we expect you to make a reasonable effort to do your part.

Lynn

[Jay.kothari]

Lynn,

         First of all dont get me wrong. I did try on my own to get the graph. And m good with the basics of LV. Its just that when I get stuck up at some points it then becomes really very difficult to come out of it and so i ask for help. You have been really helpful, kind and patient in helping me in my problems. I hope you continue to do so. Here I have attached a vi in which i have used a loop and then tried collecting the values to the X-Y graph. Please correct me where I went wrong.

Also in the VI you attached, how did u make the connection between the cluster and the XY graph. Cause in another VI am getting a bad/broken wire. Please Help !

Jay

[johnsold]

Jay,

In your Vi you only look at the last point from the loop.  You discard all previous points from earlier iterations.

Notice that in my while loop the tunnels bringing Power and RL/Rs out of the loop are white with [ ]. This means that I enabled autoindexing for those tunnels, thereby producing arrays at the outputs.  Between the while loop and the XY Graph terminal is a Bundle node from the Cluster, Class, & Variant palette.  The Help for the graph shows how this is used.

Lynn

[Jay.kothari]

Thanks a lot Lynn. Also that was very self explanatory...

Thanks again

Regards

Jay