DIODE IV CHARATERISTICS

[Jay.kothari]

Hello

I am currently stuck up while implementing  the diode characteristics using LabVIEW . I have tried ample ways to get the diode curve but my efforts are in vain. I am sincerely looking for help from you guys over here. I have attached two .vi
The diode with linear curve.vi is one in which i have achieved a linear increase of current with small increase in voltage.
The second diode ideal.vi is on in which after used ideal conditions of conducting and non conducting state.

The readings are achived using my first year journal.

I am very new to the software and would appreciate any help. i have Labview v8.5 n v10.

Thanks 🙂

[johnsold]

First some diagram clean up helps.  This is available as a menu item in LV 2010, but can be done manually in any version.

Second, the inner loop with the dV control terminal never stops.  This is because of the way numbers are represented in binary. 0.7 cannot be represented exactly as a double precision number in binary.  Depending on the values set for Vmin and dV it is likely that the two inputs to the =? comparison will very rarely be exactly equal.  Either use a >= comparison or the In Range and Coerce function with the upper and lower limits set slightly above and below 0.7.

Third. The outer loop only executes once, so why have it?

Fourth. What is the purpose of building a graph with only two points, the Y values of which are constants?

Lynn

[Jay.kothari]

Hey Lynn,

              The inner loop does stop at 0.7  value of Vmin..also...my point is to obtain a graph of a diode...for a diode circuit as soon as 0.7 V is crossed..the diode is forward biased and it starts conducting.For the same reason..for volatages below 0.7 it is in off state and does not conduct. The inner loop hence has current value as zero while for outer loop the value of volatage is constant at 0.7 while current increases byt 5ma. Could you suggest a different or a new .vi that can help me with this example..
The outer loop aint necessary..I get that..

Cheers 🙂

[johnsold · Accepted solution]

The inner loop stops at 0.7 only if you get lucky.  Add indicators connected to the 0.7 constant and to the V(t) line inside the loop.  Set the display format on both inidcators to 18 significant digits and uncheck Hide trailing zeros. Turn on execution highlighting to slow things down. Set Vmin to zero and dV to 0.05 and watch it. See the image below.

Look at this example for a somewhat simpler approach (and one which uses a more realistic diode model).  I put comments on the block diagram to explain the differences from your VI.

Lynn

[Jay.kothari]

Thank You Johnsold.
I realised my mistake. I will now be working on transistor. Do you have any material to provide with any help ?
Cheers 🙂

Thanks Again.

Regards
Jay Kothari

[johnsold]

Jay,

Decide what model you want to use then implement the appropriate equations in your VI.

Are these school assignments?

Lynn

[Jay.kothari]

Lynn,

        Yes these are my project assignments. And here its a very new software. Our aim in the end is to make all the engineering related problems and experiments graphical and thus develop and educational tool in the end.

By model I am interested in npn, pnp transistor, FET,  BJT, MOSFET, and some also digital experiments like decade counter, up down counter, ic 555, ic 741 etc. Do you have any already developed VIs of these or other basic experiments ?

Jay

[johnsold]

Jay,

I have not done any of these in LV.  You might post a message on the Circuit Design Suite Board.  I think they have some simulation capabilities.

Lynn

[Jay.kothari]

Lynn,

        But i need to work with LabVIEW and not any other software. Will posting in that section help then ?

Jay

[johnsold]

Jay,

I have not used that board much, but I think you will find that many of the participants are very knowledgeable about circuit simulation in general.  The specific language is less important than good models and algorithms.

When you have LabVIEW-specific questions, this Board is the best place.

Lynn