// C++ Arduino Code (Copy Below)

#include <Servo.h>

 

// Pins (as you used before)

const int TRIG_PIN  = 5;

const int ECHO_PIN  = 6;

const int SERVO_PIN = 9;

 

// Distances & timing

const int NEAR_CM        = 15;    // trigger distance to detect a hand

const int FAR_CM         = 18;    // small hysteresis to release detection

const unsigned long COOLDOWN_MS = 1500;  // ignore re-triggers for this time

 

// Servo angles (adjust for your mechanism)

const int OPEN_ANGLE  = 0;    // curtain open

const int CLOSE_ANGLE = 90;   // curtain closed

 

Servo curtain;

bool curtainClosed = false;    // start opened

bool wasNear = false;          // previous "near" state

unsigned long lastToggleMs = 0;

 

long readDistanceOnceCM() {

  // Send pulse

  digitalWrite(TRIG_PIN, LOW);

  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);

  delayMicroseconds(10);

  digitalWrite(TRIG_PIN, LOW);

 

  // Listen with timeout to avoid blocking forever

  unsigned long duration = pulseIn(ECHO_PIN, HIGH, 25000UL); // ~4.3 m max

  if (duration == 0) return 999; // no echo

  return (long)(duration * 0.0343 / 2.0); // cm

}

 

// Median of 3 reads for stability

long distanceCM() {

  long a = readDistanceOnceCM();

  delay(10);

  long b = readDistanceOnceCM();

  delay(10);

  long c = readDistanceOnceCM();

 

  // sort a,b,c and return median

  if (a > b) { long t=a; a=b; b=t; }

  if (b > c) { long t=b; b=c; c=t; }

  if (a > b) { long t=a; a=b; b=t; }

  return b;

}

 

void moveCurtain(bool closeIt) {

  if (closeIt) {

    curtain.write(CLOSE_ANGLE);

  } else {

    curtain.write(OPEN_ANGLE);

  }

  curtainClosed = closeIt;

}

 

void setup() {

  pinMode(TRIG_PIN, OUTPUT);

  pinMode(ECHO_PIN, INPUT);

  curtain.attach(SERVO_PIN);

 

  // Start opened

  moveCurtain(false);

}

 

void loop() {

  long d = distanceCM();

 

  // Determine current "near" with hysteresis

  bool isNear;

  if (wasNear) {

    // remain "near" until it moves past FAR_CM

    isNear = (d < FAR_CM);

  } else {

    // become "near" only when inside NEAR_CM

    isNear = (d < NEAR_CM);

  }

 

  unsigned long now = millis();

 

  // Edge-detect: far -> near and cooldown passed

  if (!wasNear && isNear && (now - lastToggleMs >= COOLDOWN_MS)) {

    moveCurtain(!curtainClosed);    // toggle

    lastToggleMs = now;

  }

 

  wasNear = isNear;

  delay(30); // small loop delay

}