Solar-Powered Motion-Activated LED Circuit Documentation

Summary

This circuit is designed to harness solar energy to charge a 9V battery, which in turn powers an Arduino UNO microcontroller along with a Light-Dependent Resistor (LDR), a Passive Infrared (PIR) motion sensor, and an LED. The Arduino UNO reads the ambient light level through the LDR and detects motion via the PIR sensor. When the environment is dark and motion is detected, the LED is turned on, indicating the presence of an individual or moving object.

Component List

Solar Panel

• Description: A photovoltaic module that converts sunlight into electrical energy.
• Pins: +, -

Solar Charge Controller

• Description: Regulates the voltage and current coming from the solar panels to charge the battery and prevent overcharging.
• Pins: Solar Cell +, Solar Cell -, Battery +, Battery -, Load +, Load -

Battery 9V

• Description: Provides energy storage for the circuit to operate when solar power is insufficient.
• Pins: VCC, GND

LDR (Light-Dependent Resistor)

• Description: A sensor that changes resistance based on the ambient light level.
• Pins: A0, D0, GND, VCC

PIR/Motion Sensor

• Description: Detects motion by measuring changes in the infrared levels emitted by surrounding objects.
• Pins: GND, OUTPUT, VCC

LED: Two Pin (red)

• Description: A red light-emitting diode used as an indicator.
• Pins: cathode, anode

Arduino UNO

• Description: A microcontroller board based on the ATmega328P, used for controlling the sensors and LED.
• Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0 to A5, SCL, SDA, AREF, D13 to D0

Wiring Details

Solar Panel

• + connected to Solar Charge Controller Solar Cell +
• - connected to Solar Charge Controller Solar Cell -

Solar Charge Controller

• Battery + connected to Battery 9V VCC
• Battery - connected to Battery 9V GND

Battery 9V

• VCC connected to Solar Charge Controller Battery +
• GND connected to Solar Charge Controller Battery -

LDR

• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND
• A0 connected to Arduino UNO A0

PIR/Motion Sensor

• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND
• OUTPUT connected to Arduino UNO D2

LED: Two Pin (red)

• anode connected to Arduino UNO D13
• cathode connected to Arduino UNO GND

Arduino UNO

• 5V connected to LDR VCC and PIR/Motion Sensor VCC
• GND connected to LED cathode, PIR/Motion Sensor GND, and LDR GND
• A0 connected to LDR A0
• D13 connected to LED anode
• D2 connected to PIR/Motion Sensor OUTPUT

Documented Code

// sketch.ino
const int ldrPin = A0; // LDR connected to A0
const int pirPin = 2;  // PIR sensor connected to D2
const int ledPin = 13; // LED connected to D13

void setup() {
  pinMode(ldrPin, INPUT); // Set LDR pin as input
  pinMode(pirPin, INPUT); // Set PIR pin as input
  pinMode(ledPin, OUTPUT); // Set LED pin as output
  Serial.begin(9600); // Initialize serial communication
}

void loop() {
  int ldrValue = analogRead(ldrPin); // Read LDR value
  int pirValue = digitalRead(pirPin); // Read PIR value

  Serial.print("LDR Value: ");
  Serial.println(ldrValue);
  Serial.print("PIR Value: ");
  Serial.println(pirValue);

  // Check if it is dark and motion is detected
  if (ldrValue < 500 && pirValue == HIGH) {
    digitalWrite(ledPin, HIGH); // Turn on LED
  } else {
    digitalWrite(ledPin, LOW); // Turn off LED
  }

  delay(1000); // Wait for 1 second
}

This code is designed to be uploaded to the Arduino UNO microcontroller. It initializes the LDR and PIR sensor as inputs and the LED as an output. The loop function continuously reads the values from the LDR and PIR sensor, printing them to the serial monitor. If the LDR value indicates low light (value below 500) and the PIR sensor detects motion (value is HIGH), the LED is turned on. Otherwise, the LED is turned off. The system pauses for 1 second between each loop iteration.