read external 6V power source via 5V driven arduino

Other Hardware Motors, Mechanics, Power and CNC
1

I need to check the external 6V voltage for a servo circuit
on my 5V USB driven arduino uno

in order to not waste power & "over-power" the arduino's
analog pin reading the external 6Vt:

  • should i use a voltage divider with high resistor values
    or rather small value resistors?

i look forward to your advice …

arduino read external 6V.jpg
arduino read external 6V.jpg989×638 108 KB

2

The Arduino ADC works best with resistors below 10k ohms - that should be high enough to keep the power loss acceptable.

...R

3

... thanks for your immediate reply!

i was a bit concerned, thought that i might need > 10k
since it's 6v external voltage connected to a 5v arduino pin
but will give it a try with <= 10k resistor combinations.

4

marc_is_curious:
since it's 6v external voltage connected to a 5v arduino pin

The purpose of the voltage divider is to ensure there is less than 5v on th Arduino pin. With a 2k and 10k resistor the 6v would be reduced to 5v so maybe 3k and 10k would be better - to give a margin of safety.

...R

5

i will try 3k and 10k:

(temporary analog output) + (test-measured real voltage - test-measured analog output)
... instead of ...
(temporary analog output) * 2

should provide a more precise value.

thanks a lot, again!