v3.6-low-solar-voltage-cutoff

/*
 * solar-charger-arduino-nano-v3
 * v3.6-low-solar-voltage-cutoff
 * Todo:
 *[x]  get tmp36 sensor working with code
 *[x]  get display working
 *[x]  display tmp36 on display
 *[x]  get mosfet driver circuit working
 *[x]  create voltage divider for solar
 *[x]  create voltage divider for battery
 *[x]  get current sensor working on solar
 *[x]  create sleep arduino when low solar voltage
 *[ ]  create sleep arduino when battery voltage is less than 6V
 *[ ]  create cut off solar panel when battery voltage is 9V
 *[ ]  create cut off solar panel based on temp increase (perhaps +10c?)
 */
#include <Wire.h>
#include <Adafruit_INA219.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_GFX.h>
#include "LowPower.h"
Adafruit_INA219 ina219;

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define pwmMax 255
#define sensorPin A0

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

int pwmPin = 6;
float batteryMaxV = 9;
float solarVoltage = 0.0;
float batteryVoltage = 0.0;

void setup()
{
    Serial.begin(9600);
    pinMode(pwmPin,OUTPUT);
    TCCR1B = TCCR1B & B11111000 | B00000101;  // 30Hz Pin 9 & 10
    TCCR0B = TCCR0B & 0b11111000 | 0x05 ; // 61Hz Pin 5 & 6 

    if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) 
    { 
      // Address 0x3D for 128x64
      Serial.println(F("SSD1306 allocation failed"));
    }
    display.clearDisplay();
    display.ssd1306_command(SSD1306_SETCONTRAST);
    display.ssd1306_command(10); // Where c is a value from 0 to 255 (sets contrast e.g. brightness)

    uint32_t currentFrequency;
    ina219.begin();
}

void loop()
{
  /*******************Current Sensor***********************/
  float shuntvoltage = 0;
  float busvoltage = 0;
  float current_mA = 0;
  float loadvoltage = 0;
  float power_mW = 0;
  float power_W = 0;

  shuntvoltage = ina219.getShuntVoltage_mV();
  busvoltage = ina219.getBusVoltage_V();
  current_mA = ina219.getCurrent_mA();
  power_mW = ina219.getPower_mW();
  loadvoltage = busvoltage + (shuntvoltage / 1000);
  power_W = power_mW / 1000;
  
  Serial.print("Bus Voltage:   "); Serial.print(busvoltage); Serial.println(" V");
  Serial.print("Shunt Voltage: "); Serial.print(shuntvoltage); Serial.println(" mV");
  Serial.print("Load Voltage:  "); Serial.print(loadvoltage); Serial.println(" V");
  Serial.print("Current:       "); Serial.print(current_mA); Serial.println(" mA");
  Serial.print("Power:         "); Serial.print(power_mW); Serial.println(" mW");
  Serial.println("");
  
  /*******************Voltage Reads***********************/
  int sampleCount = 0;
  while (sampleCount < 50) 
  {
    solarVoltage += analogRead(A3);
    batteryVoltage += analogRead(A2);
    sampleCount++;
    delay(5);
  }
  /*
   * read the voltage from the two voltage dividers, for solar and battery voltages
   * Divide by 50 samples
   * Multiply by 5V 
   * Divide by 1024 ADC values
   * Multiply by division factor R1 / R2 ... R1 = 10k , R2 = 1k
  */
  solarVoltage = (((float)solarVoltage / 50) * 4.7) / 1024.0 * 11;
  batteryVoltage = (((float)batteryVoltage / 50) * 4.7) / 1024.0 * 11;

  /*******************PWM Duty Cycle***********************/
  //duty cycle is inversed by mosfet, 
  //so 90% duty cycle = 10% on.
  //10% duty cycle = 90% on.
  analogWrite(pwmPin, pwmMax * 0.05); //5% duty cycle or on 95%

  /*******************Temperature Reading***********************/
  // Get a reading from the temperature sensor:
  int reading = analogRead(sensorPin);

  // Convert the reading into voltage:
  float voltage = reading * (5000 / 1024.0);

  // Convert the voltage into the temperature in Celsius:
  float temperature = (voltage - 500) / 10;

  /*******************Display***********************/
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0, 10);
  display.print("Battery V: ");
  display.print(batteryVoltage);
  display.println("V");
  //display.println("-------");
  display.print("Solar V: ");
  display.print(solarVoltage);
  display.println("V");
  //display.println("-------");
  display.print("Solar I:");
  display.print(current_mA);
  display.println("mA");
  //display.println("-------");
  display.print("Solar Pwr:");
  display.print(power_W);
  display.println("W");
  //display.println("-------");
  display.display();
  display.clearDisplay();
  delay(50);

   /*******************Sleep Arduino When Low Solar***********************/
   /*
    * If the current from the panel is under 30mA:
    *   Wait 1 second to check the current wasn't an erronous error.
    *   If still under 30mA; 
    *   - Display error to OLED
    *   - Switch off MOSFET with 100% duty cycle
    *   - Turn off OLED display
    *   - Sleep Arduino for 64 seconds
    */
   
  if (current_mA < 30)
  {
    delay(1000);
    current_mA = ina219.getCurrent_mA();
    if (current_mA < 30)
    {
      display.clearDisplay();
      display.setTextSize(2);
      display.setCursor(0, 10);
      display.println("ERROR!");
      display.print("Low Solar Voltage");
      display.display();
      delay(200);
      display.clearDisplay();
      analogWrite(pwmPin, pwmMax); //Switch off MOSFET with 100% duty cycle
      display.ssd1306_command(SSD1306_DISPLAYOFF);
      for (int i = 0; i < 1; i++) // 8 seconds * 8 = 64 seconds
//MUST CHANGE THE 1 FOR TESTING TO 8 LOOPS
      {
        LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
      }
      display.ssd1306_command(SSD1306_DISPLAYON);
    }
  }
}