ESP32 voltage divider for ADC question

[brebisson]

Hello,

I use an ESP32 and I want to measure the voltage of a 12V input power supply/battery.
I placed a 11 to 1 divider bridge using a 10K/100K pair of resistor, but I seem to be getting weird readings...

I am not at all good in electronics. Am I doing something wrong that is causing my bad readings? Should I use other values for my resistors?

Thanks,
Cyrille

[Rogga10000!]

Hi Cyrille,
I use this voltage divider to do my first high level calculations. After that, I do practical test using the serial monitor and a multimeter. The reason for this is because R2 will be in parallel with the internal resistance of the microcontroller)

I then put the values in a diagram. The values from the serial monitor on the x-axis and the values from the multimeter on the y-axis.

Then you should have a linear function. You then use the equation of the straight line (y=kX+m) to get the right figures.

Good luck!
Roger


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