Monitor Battery Level

Using Arduino Programming Questions
1

hi i am using arduino one and want to see the charge level of the battery.

I'm using an 8v battery and one voltage divider:

vi = 8v,
R1 = 1000
R2 = 1000

I am using this code but not work for me, does not yield the correct values.
any ideas?

const int referenceVolts = 5; // the default reference on a 5-volt board
const int R1 = 1000; // value for a maximum voltage of 20 volts
const int R2 = 1000;
// determine by voltage divider resistors, see text
const int resistorFactor = 255 / (R2/(R1 + R2));
const int batteryPin = A0; // +V from battery is connected to analog pin 0

void setup()
{
Serial.begin(115200);
}

void loop()
{
int val = analogRead(batteryPin); // read the value from the sensor
float volts =  (val / resistorFactor) * referenceVolts ; // calculate the ratio
Serial.println(volts); // print the value in volts
delay(500);
}

708×840 38.5 KB

2

http://arduino.cc/en/Reference/AnalogRead

3

const int referenceVolts = 5; // the default reference on a 5-volt board
should be
const int referenceVolts = 5.0; // the default reference on a 5-volt board

Need a decimal in the equation.

Try:
int val = analogRead(batteryPin); // read the value from the sensor
float volts = (val*2.0 / 1023.0) * 5.0 ; // calculate the ratio
Serial.println(volts); // print the value in volts
delay(500);

4

not work for me.
so I have connected to the Arduino, please help

5

Works fine here on UNO.

Put .1uf cap as close as possible on the input to ground on the regulator.
What colors are on your resistors?

6

LarryD:
Works fine here on UNO.

Put .1uf cap as close as possible on the input to ground on the regulator.
What colors are on your resistors?

1.5 K,

BROWN, GREEN , RED, GOLD

7

Hi, do you have a meter to measure voltage, ie a DMM.
Check what the voltage is from gnd to A0.

Tom..... :slight_smile: