LTSpice variable Resistor with voltage and current

Thread Starter

ulix

Joined May 21, 2015
8
Hello,

I want to simulate a variable resistor, for which I have the current and voltage date (0V, 0.5V, 1V, 2V, 4V, 6V, 8V, 10V) How can I get this realized? Everything I tested didn't get me in the simulation on the x-axes the voltage and on the y-axes the current...
cheers
 

MikeML

Joined Oct 2, 2009
5,444
Is the resistor non-linear ( a function of the voltage across it), or do you just want to vary the resistor to see what effect that has on the operation of the circuit?
 

Alec_t

Joined Sep 17, 2013
14,280
I suggest you plot your data and from the graph deduce an equation which gives resistance as a function of current or voltage. Then use that equation to set the sim resistor value.
 

Thread Starter

ulix

Joined May 21, 2015
8
How can I get the function? Is there no other way? In PSpice it works with the GTABLE Command, you put TABLE = (u_1, i_1) (u_2, i_2) ....
 

Attachments

Last edited:

Thread Starter

ulix

Joined May 21, 2015
8
Well, my function is: f(x)=-5.7942*10^-4 * x^2 + 0.01416x + 7.3299*10^-3. But it doesn't replay the correct value. Can I display the voltage current as function in ltspice?
The right value is: V(vr)=1.695V and 31.8mA
 

Attachments

Thread Starter

ulix

Joined May 21, 2015
8
Alec_t you are great, mate! I got it. I read your post again, I didn't make a function for R, at first I did it for I.
cheers!
 

MikeML

Joined Oct 2, 2009
5,444
Well, my function is: f(x)=-5.7942*10^-4 * x^2 + 0.01416x + 7.3299*10^-3. But it doesn't replay the correct value. Can I display the voltage current as function in ltspice?
...
Sure, just plot the expression V(vr)/I(R5).

Here is an example of how to make a resistor a function of a node voltage in LTSpice. I also show how to plot the resistance of R1.


219.gif

I am guessing that your function R=f(x) is not correct. I sure doesn't resemble any light bulb I have ever modeled.
 
Top