resistors in a circuit

i was trying to find the amont of the resistor for my circuit based on a function i have, these two resistors are in parallel, can someone please explain me how to write the right function for it to get the amount of the resistors?

here is the eqution i used 1.24 = minimum voltage * ( ( R1 || R2 ) / ( R3 + R1 || R2 ) ).

[Shubham Gupta]

Do you mean something like this ?

ResistorAmount = R1*R2/(R1*R2 + R2*R3 + R3*R1);

Not sure how the equation that you have mentioned works ?

[mohammad nazari]

The equation is suppose to give me the amount of R1 and R2 by giving it the amount of R3 and minimum voltage, just couldn't figure out how to sort it in MATLAB.

Answer 1

[Shubham Gupta]

Try this :

r3 = 100; % for example
Volt_func =  @(r)1.24*(r(1)*r(2)+r(2)*r3+r3*r(1))/r(1)/r(2);

rout = lsqnonlin(Volt_func,[50,55])
r1 = rout(1);
r2 = rout(2);

Note : "lsqnonlin" can only be used if you have optimization toolbox. If not, there are few other functions that don't need optimization toolbox.

http://www.mathworks.com/help/matlab/optimization.html

[mohammad nazari]

no actually the R1 and R2 are not multiolied they are in parallel in a circuit.

[Shubham Gupta]

But if R1 & R2 are parallel, then it's equivalent resistance is calculated by :

R1 || R2 = R1*R2/(R1+R2) , isn't it? If that's not true, I am not sure what "parallel in a cicuit" means?