Interfacing Photoresistor With ESP32

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• ESP32 Development Board
• Photoresistor or Light-dependent-resistor (LDR)
• 5mm LED
• 100Ω Resistor
• 10kΩ Resistor
• 4 pieces of jumper wires
• Breadboard

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Wiring the LED to the ESP32 board

• Wire the GND pin from the ESP32 development board to the blue rail on the breadboard to create a common ground rail.
• Connect the flat edge of the LED (also known as the cathode) to the common ground on the Arduino.
• Connect the rounded edge of the LED (also known as the anode) to a 100Ωresistor.
• Then, connect the free-end of this resistor to pin D5 on the ESP32, shown as the orange wire.

Wiring the photoresistor to the ESP32 board using a voltage divider

• Connect one of the pins of the photoresistor to a 10kΩ resistor. Then connect the same end to pin D2 on the ESP32 board, shown as the white wire.
• Connect the free-end of the resistor to the common ground.
• Then, connect the free-end of the photoresistor to the 3.3V pin, shown as the red pin.

/**
 * Interfacing Photoresistor using ESP32
 * By TechMartian
 *
 */

/cosntants for the pins where sensors are plugged into.
const int sensorPin = 2;
const int ledPin = 5;

//Set up some global variables for the light level an initial value.
int lightInit;  // initial value
int lightVal;   // light reading

void setup()
{
  // We'll set up the LED pin to be an output.
  pinMode(ledPin, OUTPUT);
  lightInit = analogRead(sensorPin);
  //we will take a single reading from the light sensor and store it in the lightCal        //variable. This will give us a prelinary value to compare against in the loop
}

void loop()
{

  lightVal = analogRead(sensorPin); // read the current light levels

  //if lightVal is less than our initial reading withing a threshold then it is dark.
  if(lightVal - lightInit <  50)
  {
      digitalWrite (ledPin, HIGH); // turn on light
  }

  //otherwise, it is bright
  else
  {
    digitalWrite (ledPin, LOW); // turn off light
  }

}

Attachments

• lesson_3-photoresistor.ino
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