#include <Servo.h>

int ldrPin = A3;

// LDR Characteristics
const float GAMMA = 0.7;
const float RL10 = 50;

Servo lightMeter; 

void setup() {
  lightMeter.attach(9); 
  pinMode(ldrPin, INPUT);
  Serial.begin(115200);
}

void loop() {
  int ldrStatus = analogRead(ldrPin);

  float voltage = ldrStatus / 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));

  float angle = map (lux, 0, 100000 ,0, 180); 

  lightMeter.write(angle); 
}