Hi. So I have an arduino system of wheels, servos, and leds. These sure consume a lot of power. I want my arduino to tell me wether its battery is running low, maybe by switching on led 13. My problem is I dont know how to measure arduino power supply.
Based on my electrical and arduino experience, if I have 9v battery, I will use a voltage divider to step it down to 5v, then plug that to an analog pin. My THEORY is that it will work like a potentiometer, then once the battery falls 1v then it will tell me to change or charge the batteries
Is my theory correct? If not, I kindly ask for your suggestions?
Yup, that's how its normally done. A 1:1 divider with 18k resistors will reduce 10V to 5V and have an impedance less than 10k which will ensure accurate ADC readings.
A freshly charged NiMH cell measured open circuit is "around " 1.4V - depending on temperature.
Shape of Discharge Curve
A typical discharge profile for a battery discharged at the 5-hour rate (the 0.2C rate) is shown in (Fig. 6).
The initial drop from an open-circuit voltage of approximately 1.4 volts to the 1.2 volt plateau occurs rapidly.
Li-ion rechargeable cells have a different characteristic and dont show the "plateau" that NiMH cells do.
Its important not to over-discharge so you should turn offf if the cell voltage drops below 3.0V
Thats why cells in series should ALL be measured.
