Pololu Robotics & Electronics
Menu
My account Comments or questions? About Pololu Contact Ordering information Distributors

Problem adjusting Pololu Boost Regulator 4-25V


#1

I have problems adjusting the potentiometer to obtain an stable 18.0 v output. the potentiometer is extremely sensible, and the most minimal movement causes a ±0.5v variation at the output, so it’s really hard to get the desired value and because of this, the output voltage would be likely unastable, taking into account that the regulator will be instaled in a robot.

this only happens when the output voltage is being setting above 14v aproxemily. The input is connected to an 3S 11.1v Lipo battery, with a 47uF capacitor. The load is an 1k resistor.

What could I do to solve the problem? I can replace the potentiometer with smd resistances, what values should I use to get 18.0v at the output?

Thanks.


#2

Hi.

I am sorry you are having a hard time adjusting the output of your regulator. Because the potentiometer adjustment not linear, there is less resolution for setting output voltages near the top of the regulator’s range. To get a fixed output voltage of 18V you could replace the potentiometer with two resistors of about 9.5k between the top pad and wiper and 400ohms between the bottom pad and wiper. I have marked the wiper and top potentiometer connections in the picture below.

reg04a_fixed_pot

By the way, if you are able to adjust it to a point you are happy with, you might consider using glue to fix the potentiometer in place rather than changing the potentiometer for resistors.

-Claire


#3

Thank you Claire!

But that regulator is not the product I’m asking. the regulator that I bought is this:

The resistors values that you recommend are still valid for this product?


#4

Oops! Sorry, I accidentally misread that you had one of our 4-25V step-down regulators.

To get a fixed 18V out of the #799 step-up regulator, you can replace the potentiometer with two resistors of about 97-100k between the top pad and wiper and 3k between the bottom pad and wiper. Here is the labeled picture of the correct regulator:

reg03a_fixed_pot

-Claire


#5

Hello, I have the same problem. I need fixed 12.4 V between 12.6 Voltage output from #799. My lipo is 2S (7.4 V) So when i adjust the voltage, after using my robot 2-3 times, voltage changing because of the vibration. Can you help me which resistors i need to use ?

Thank you.


#6

Hi, Reaven.

To get an output voltage between 12.4V and 12.6V, you should use a top resistor of 91k and a bottom resistor of 7.32k or 7.5k.

-Claire


#7

Top - Wiper - 91 K
Bottom - Wiper 7,32 - 7,5 K right ? Wiper is the common point rihgt ?


#8

Hi, Reaven.

Yes, that is right.

Kevin