Oki, great information! I will consider it in the future. Although i have spent countless hours reading about the LM317, I am yet to find any information that says to use max 120Ω. Quite the contrary actually, as you can see in guides and tutorials for the LM317, people use resistors hugely different to 120Ω. But thanks for pointing it out nonetheless.
Edit: Ok i tested myself now and see the point of using <=120Ω for R1 now. Then the regulator shows the desired Vout even without any load on it.. But as soon as a regulator with R1 >120Ω gets load on it (tested with a 0,1A fan) it starts producing the desired Vout. I will use <=120Ω in the future. Thanks!
So, if we put all that aside now, I would be really happy for a solution to my original topic.
And to clarify, i will make a recap.
√ Vout can be calculated knowing the values of R1 and R2.
√ R1 can be calculated knowing the Vout i want and R2.
X R2 can be calculated the same way but knowing the Vout and value of R1, however, i need help with breaking out R1 from the original formula Vout= 1,25*(1+(R2/R1)) + Iadj*R2
To make it even clearer, lets put values for Vout and R1.
Vout = 12,5v
R1 = 120Ω
R2 =
x
Which makes: 12,5=1,25*(1+(
x/120))+((50*10^-6)*
x)
Solve
X