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BrianG · 03.30.2010, 12:26 AM

Squee, after using a few resistor values and analyzing the results, it appears the formulas are:

R=(V-5)/0.000533

V=R*0.000533+5

V = the output voltage you want.
R = the resistor
5 = the base regulator rating

So, for 7v, the resistor needed is 3752 ohms. The closest common value is 3.3k, which would give you around 6.75v. If you want exactly 7v, find some way to shoehorn a 5k ohm pot in there, adjust it, and then glue it so it doesn't move. I would prefer an actual resistor to prevent the pot from getting dirty and causing issues (like the output going to full input voltage). A 3.3k ohm in series with a 470 would work.

Be warned, the inductor value does play a critical role. If you choose a voltage too far away from 5v, "bad" things may happen. From what I've seen for the datasheet for the adjustable versions, each inductor value is good for a range. I would definitely bench test it under load to make sure it's ok before you risk a servo/receiver.

	(#4)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	03.30.2010, 12:26 AM Squee, after using a few resistor values and analyzing the results, it appears the formulas are: R=(V-5)/0.000533 V=R0.000533+5 V = the output voltage you want. R = the resistor 5 = the base regulator rating So, for 7v, the resistor needed is 3752 ohms. The closest common value is 3.3k, which would give you around 6.75v. If you want exactly 7v, find some way to shoehorn a 5k ohm pot in there, adjust it, and then glue it so it doesn't move. I would prefer an actual resistor to prevent the pot from getting dirty and causing issues (like the output going to full input voltage). A 3.3k ohm in series with a 470 would work. Be warned*, the inductor value does play a critical role. If you choose a voltage too far away from 5v, "bad" things may happen. From what I've seen for the datasheet for the adjustable versions, each inductor value is good for a range. I would definitely bench test it under load to make sure it's ok before you risk a servo/receiver.