Motion Sensor Activated Light With Automatic Brightness Adjustment | Arduino + PIR + LDR

So today I am planning to put an end this struggle. In this project, we are going to make a PIR based motion sensor activated light and using an LDR (photoresistor) to automatically adjust the brightness of the light ie at night the light will be in full brightness and in the morning if the sunlight is low then the light will automatically turn on with a suitable brightness if motion is detected.

LDR With Arduino

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Video

Hardware Required

Components	Amazon	AliExpress	Banggood
Arduino Nano
LDR (photoresistor)
PIR Motion Sensor
TIP120 Transistor

Circuit

• Connect GND to Arduino GND, PIR GND, and Emitter of TIP120.
• Connect 5v to one of the terminals of LDR and VCC of PIR.
• Connect the other terminal of LDR to pin A7 of Arduino.
• Connect the OUT of PIR to pin D2 of Arduino
• Connect the Base of TIP120 to Arduino pin D3 via a 1k ohm 1/4w resistor.
• Connect a 10k ohm 1/4w resistor from pin A7 of Arduino to the GND.
• Finally, connect the negative of Light to the Collector of TIP120 and positive of Light directly to the 12v supply.
• Also, don’t forget to give power to Arduino.

Code

#define LDR A7
#define PIR 2
#define Light 3

int LDRvalue;
long counter;

void setup() {
  pinMode(PIR, INPUT);
  pinMode(Light, OUTPUT);
}

void loop() {
  if (digitalRead(PIR) == HIGH)
  {
    counter =0;
    LDRvalue = map(analogRead(LDR), 0, 1024, 254, 0);
    delay(50);
    analogWrite(Light,LDRvalue);
  }
  else
    counter++;
  if (counter <= 10000)
    digitalWrite(Light, LOW);
}