What's the formula for working out the resistance needed for various voltages with the LM317 regulator running off a 12V supply?
Is this what you're after? Vout=1.25*(1+R2/R1) I believe there will be at least a 1.5v voltage drop from 12v using that regulator btw.
Yep, that looks about right, but I thought there was something to do with the current across R2 or something. Yeah, I know it won't hit the full 12V.
There's a little bit at the end of the equation dealing w/ current across R2, but the value is negligible enough to not even concern yourself over it.
Excellent thanks Am I right in thinking that when there's no load on the output that the voltage will shoot up?
Accuracy & Precision is our watchwords. The bit on the end is +Iq x R2, but Iq is around 50uA, so if R2 is 5k it makes 0.25v difference. Not a problem with a pot, but using resistors to get a voltage you may as well do the full sum. Providing you use lowish value resistors for R1 & R2 they'll draw enough current for good regulation with no (other) load. The 240R usually shown for R1 will do that.
