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/*--------------------------------------------------------------
  Program:      volt_measure

  Description:  Reads value on analog input A2 and calculates
                the voltage assuming that a voltage divider
                network on the pin divides by 11.
  
  Hardware:     Arduino Uno with voltage divider on A2.
                
  Software:     Developed using Arduino 1.0.5 software
                Should be compatible with Arduino 1.0 +

  Date:         22 May 2013
 
  Author:       W.A. Smith, http://startingelectronics.com
--------------------------------------------------------------*/
#include <LiquidCrystal.h>

//            R1          R2 
//   Vin ----/\/\/\----*----/\/\/\---- GND 
//                     | 
//                     | Vout 
//                     | 
//                ANALOG PIN  
// * Vin : input voltage (the voltage we try to meter)
// * Vmax : the maximum value of the input voltage
// * Vout : the output voltage (the Vin remapped to 0 .. 1.1V)

// Choose R1 and R2 CAREFULLY according to the following rule:

// R1 = R2 x 1.1 / (Vmax - 1.1)
// R2 = R1 x (Vmax - 1.1) / 1.1

// A typical configuration is R1 = 1k and R2 = 4k. It assumes Vmax = 5.5V. 

// number of analog samples to take per reading
#define NUM_SAMPLES 10

int sum = 0;                    // sum of samples taken
unsigned char sample_count = 0; // current sample number
float voltage = 0.0;            // calculated voltage

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup()
{
    Serial.begin(9600);
}

void loop()
{
    // take a number of analog samples and add them up
    while (sample_count < NUM_SAMPLES) {
        sum += analogRead(A2);
        sample_count++;
        delay(100);
    }
    // calculate the voltage
    // use 5.0 for a 5.0V ADC reference voltage
    // 5.015V is the calibrated reference voltage
    voltage = ((float)sum / (float)NUM_SAMPLES * 5.015) / 1024.0;
    // send voltage for display on Serial Monitor
    // voltage multiplied by 11 when using voltage divider that
    // divides by 11. 11.132 is the calibrated voltage divide
    // value
    lcd.begin(16, 2);
    lcd.print("  Volt= ");
    lcd.print(voltage * 9.1);
    lcd.print("V");
    
    Serial.print(voltage * 9.1);
    Serial.println (" V");

    sample_count = 0;
    sum = 0;
}