// Measures solar panel voltage, current, and calculated power output
 
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <SoftwareSerial.h>
 
// ----- Pin Definitions -----
#define voltagePin A0
#define currentPin A1
 
LiquidCrystal_I2C lcd(0x27, 16, 2);
SoftwareSerial espSerial(10, 11); // RX, TX for ESP8266
 
// ----- Calibration Constants -----
const float voltageDividerRatio = 5.0; // Adjust based on your voltage sensor's resistor ratio
| const float acsSensitivity = 0.185; | // V per Amp for the ACS712 30A variant |
| --- | --- |
| const float acsZeroPoint = 2.5; | // Zero-current voltage midpoint |
 
void setup() {
  lcd.init();
  lcd.backlight();
  lcd.print("Solar Monitor");
 
  espSerial.begin(9600);
  Serial.begin(9600);
  delay(1500);
  lcd.clear();
}
 
void loop() {
  float voltage = readVoltage();
  float current = readCurrent();
  float power = voltage * current;
 
  updateDisplay(voltage, current, power);
  sendToCloud(voltage, current, power);
 
  delay(2000); // Wait before next reading cycle
}
 
// Reads and scales the panel voltage using the voltage sensor
float readVoltage() {
  int rawValue = analogRead(voltagePin);
  float sensorVoltage = (rawValue / 1023.0) * 5.0;
  return sensorVoltage * voltageDividerRatio;
}
 
// Reads and calculates current using the ACS712 sensor
float readCurrent() {
  int rawValue = analogRead(currentPin);
  float sensorVoltage = (rawValue / 1023.0) * 5.0;
  return (sensorVoltage - acsZeroPoint) / acsSensitivity;
}
 
// Updates the LCD with voltage, current, and power readings
void updateDisplay(float voltage, float current, float power) {
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("V:" + String(voltage, 1) + " I:" + String(current, 2));
  lcd.setCursor(0, 1);
  lcd.print("Power: " + String(power, 1) + " W");
}
 
// Sends the calculated readings to the cloud dashboard
void sendToCloud(float voltage, float current, float power) {
  espSerial.print(voltage); espSerial.print(",");
  espSerial.print(current); espSerial.print(",");
  espSerial.println(power); // ESP8266 firmware forwards this to ThingSpeak/Blynk