So I have the following LED circuit:
I know how to find the forward voltage and current from the datasheet of the LED and how to then solve for the appropriate value of \$R\$.
However, what I really want to do is fix the resistor value at \$R=100\$ (I'm just picking a resistor value that exists in a kit I have) and solve for \$I_F\$:
The only way I can currently think of to solve this is:
$$V_F+V_R=V_{CC}-V_{OL}$$ $$V_F+I_FR=V_{CC}-V_{OL}$$ $$V_F+100I_F=4.3$$
I found \$(V_F,I_F)=\{(2.3, 20), (2.8,15)\}\$ to be 2 arbitrary solutions to the equation. Then I graphed a line on the VI plot to determine all possible solutions to the equation. Finally I found the intersection of the line and the VI plot to determine what was the true solution to the equation is.
From this it looks like \$V_F=2.1\$ and \$I_F=22\$.
However, this was a lot of work for such a basic circuit. Is there an easier way to solve for or at least nicely estimate what \$I_F\$ would be given \$R\$? The value of the current matters a lot to me because I need to make sure I don't fry my microcontroller!
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