Arduino program to Design a night lamp using a photodiode and a LED and find out the time delay associated with turning the lamp on and off.

Arduino program to Design a night lamp using a photodiode and a LED and find out the time delay associated with turning the lamp on and off.

Designing a night lamp using a photodiode and an LED with an Arduino Uno involves several steps, including wiring the components, writing the Arduino code, and measuring the time delays. Here is a detailed guide to help you through the process:

Components Needed:

• Arduino Uno
• Photodiode
• LED
• 220-ohm resistor
• 10k-ohm resistor
• Jumper wires

Circuit Diagram:

Photodiode Circuit:

• Connect the anode (positive) of the photodiode to the 5V pin of the Arduino.
• Connect the cathode (negative) of the photodiode to one end of a 10k-ohm resistor and to the Analog pin A0 of the Arduino.
• Connect the other end of the 10k-ohm resistor to the GND pin of the Arduino.

LED Circuit:

• Connect the anode (positive) of the LED to a digital pin (e.g., D9) on the Arduino through a 220-ohm resistor.
• Connect the cathode (negative) of the LED to the GND pin of the Arduino.

const int photodiodePin = A0;
const int ledPin = 13;
int sensorValue = 0;
int threshold = 50; // Adjust this value based on your ambient light
unsigned long turnOnTime = 0;
unsigned long turnOffTime = 0;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  sensorValue = analogRead(photodiodePin);
  Serial.println(sensorValue);
  
  if (sensorValue < threshold) {
    if (digitalRead(ledPin) == LOW) {
      turnOnTime = millis();
      Serial.print("LED turned on at: ");
      Serial.println(turnOnTime);
    }
    digitalWrite(ledPin, HIGH); // Turn on the LED
  } else {
    if (digitalRead(ledPin) == HIGH) {
      turnOffTime = millis();
      Serial.print("LED turned off at: ");
      Serial.println(turnOffTime);
    }
    digitalWrite(ledPin, LOW);  // Turn off the LED
  }

  delay(100); // Delay for stability
}

Threshold Adjustment:

• The threshold variable determines the light level at which the LED should turn on or off. You may need to adjust this value based on your specific environment.

Time Recording:

• turnOnTime and turnOffTime are used to record the time when the LED state changes.
• millis() function returns the number of milliseconds since the Arduino board began running the current program.

Serial Output:

• The Serial.print and Serial.println functions are used to output the times to the Serial Monitor for observation.