Automatic Power Source Selector (Mains / Solar / Generator) using Arduino

 

🎯 Project Objective

To automatically switch the load to the available power source in the following priority order:

1. Mains Power (Highest Priority)

2. Solar Inverter

3. Generator (Backup)

No manual switching required.

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🧠 Working Principle (Simple)

• Arduino continuously checks voltage availability of:

  • Mains

  • Solar Inverter

  • Generator

• Based on priority:

  • If Mains ON → Load connects to Mains

  • Else if Solar ON → Load connects to Solar

  • Else if Generator ON → Load connects to Generator

• Switching is done using relay modules

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🧩 Required Components

Component	Quantity
Arduino UNO / Nano	1
5V Relay Module (3-Channel)	1
AC Voltage Sensor / Optocoupler (PC817)	3
Resistors (1k, 10k)	As needed
Diodes (1N4007)	3
LED Indicators	3
Buzzer (Optional)	1
AC Sources (Mains, Solar, Generator)	—
Load (Bulb/Fan)	1

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🔄 System Block Diagram

 MAINS AC ──┐
            │
 SOLAR AC ──┼──> Voltage Sensors ──> Arduino UNO
            │
 GENERATOR ─┘

 Arduino Outputs
   │
   ├── Relay 1 → Mains
   ├── Relay 2 → Solar
   └── Relay 3 → Generator

 Selected Source ──> LOAD

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⚡ Circuit Diagram (Text Representation)

MAINS AC ----[Optocoupler]---- D2 (Arduino)
SOLAR AC ----[Optocoupler]---- D3 (Arduino)
GEN AC  ----[Optocoupler]---- D4 (Arduino)

Arduino D8 ---- Relay 1 (Mains)
Arduino D9 ---- Relay 2 (Solar)
Arduino D10 --- Relay 3 (Generator)

Relay COM → Load
Relay NO  → Respective Power Source

⚠ Important:
Never connect AC directly to Arduino. Use Optocouplers / Voltage Sensors only.

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🧑‍💻 Arduino Code (Working)

// Auto Power Source Switching System

int mainsPin = 2;
int solarPin = 3;
int genPin   = 4;

int relayMains = 8;
int relaySolar = 9;
int relayGen   = 10;

void setup() {
  pinMode(mainsPin, INPUT);
  pinMode(solarPin, INPUT);
  pinMode(genPin, INPUT);

  pinMode(relayMains, OUTPUT);
  pinMode(relaySolar, OUTPUT);
  pinMode(relayGen, OUTPUT);

  digitalWrite(relayMains, LOW);
  digitalWrite(relaySolar, LOW);
  digitalWrite(relayGen, LOW);
}

void loop() {

  int mains = digitalRead(mainsPin);
  int solar = digitalRead(solarPin);
  int gen   = digitalRead(genPin);

  if (mains == HIGH) {
    switchMains();
  }
  else if (solar == HIGH) {
    switchSolar();
  }
  else if (gen == HIGH) {
    switchGenerator();
  }
  else {
    allOff();
  }
}

void switchMains() {
  digitalWrite(relayMains, HIGH);
  digitalWrite(relaySolar, LOW);
  digitalWrite(relayGen, LOW);
}

void switchSolar() {
  digitalWrite(relayMains, LOW);
  digitalWrite(relaySolar, HIGH);
  digitalWrite(relayGen, LOW);
}

void switchGenerator() {
  digitalWrite(relayMains, LOW);
  digitalWrite(relaySolar, LOW);
  digitalWrite(relayGen, HIGH);
}

void allOff() {
  digitalWrite(relayMains, LOW);
  digitalWrite(relaySolar, LOW);
  digitalWrite(relayGen, LOW);
}

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 Example Scenario

Mains	Solar	Generator	Output
ON	ON	ON	Mains
OFF	ON	ON	Solar
OFF	OFF	ON	Generator
OFF	OFF	OFF	Power OFF

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📌 Applications

• Home UPS systems

• Solar power systems

• Industries & factories

• Hospitals

• Rural electrification