Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post

meelis11 · 03-31-2011, 05:54 PM

Here is my working function:
Voltage divider ratio could be bigger but I had these resistors and it is working.
* correct R1 and R2 value to resistor values you use. For calibration, you can fine-tune these numbers
* you also must define voltagePin with correct pin number

Code:

#define voltagePin   2

unsigned long batteryVoltage(void){
   float vout = 0.0;
   float vin = 0.0;
   float R1 = 21500.0;    // !! resistance of R1 !!
   float R2 = 9500.0;     // !! resistance of R2 !!
   int value = 0;

   value = analogRead(voltagePin);
   vout = (value * 5.0) / 1024.0;
   vin = vout / (R2/(R1+R2));

   return vin * 1000;
}

Schematic is like this.
12V...R1...VoltagePin...R2...GND
so it means R1 is between 12V and VoltagePin, R2 is between VoltagePin and GND

03-31-2011, 05:54 PM	#18 (permalink)
meelis11 EcoModding Apprentice Join Date: Feb 2009 Location: Estonia Posts: 199 Green frog - '97 Audi A4 Avant 1.9TDI 81kW Diesel 90 day: 43.1 mpg (US) Thanks: 19 Thanked 40 Times in 28 Posts	Here is my working function: Voltage divider ratio could be bigger but I had these resistors and it is working. * correct R1 and R2 value to resistor values you use. For calibration, you can fine-tune these numbers * you also must define voltagePin with correct pin number Code: #define voltagePin 2 unsigned long batteryVoltage(void){ float vout = 0.0; float vin = 0.0; float R1 = 21500.0; // !! resistance of R1 !! float R2 = 9500.0; // !! resistance of R2 !! int value = 0; value = analogRead(voltagePin); vout = (value * 5.0) / 1024.0; vin = vout / (R2/(R1+R2)); return vin * 1000; } Schematic is like this. 12V...R1...VoltagePin...R2...GND so it means R1 is between 12V and VoltagePin, R2 is between VoltagePin and GND Last edited by meelis11; 03-31-2011 at 06:02 PM..