hello everyone. I would like to know how we can calculate the resistor value attached to the Arduino and the battery (2.2Kohms).
I know that we use the voltage divider but I just can't figure it out and I know that the maximum current that I can draw from an Arduino pin is 40 mA. If someone plz could help me get this right.
I want to test cell batteries using this schematic from the 65 projects book.
??
A voltage divider requires two or more resistors. R4 in your circuit doesn't do anything.
A better battery tester would be to apply a brief load on the battery, then measure the voltage. The unloaded voltage only tells you if the battery is truly dead beyond all use. Coin-cell batteries will measure good unloaded but drop in voltage very fast under load. I.E., dead.
In my opinion, this circuit is worthless for measuring coin cells.
