Ultrasonic light switch

ultrasonic-switch.c

#include <NewPing.h>

#define TRIGGER_PIN  5  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     4  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 400 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

int usual_dist;
float acc_dist;
unsigned long last_hit=0;

void setup() {
  pinMode(A3, OUTPUT);
//  digitalWrite(A3, HIGH);
  digitalWrite(A3, LOW);
  Serial.begin(9600); // Open serial monitor at 115200 baud to see ping results.
  pinMode(6, OUTPUT); // VCC pin
  pinMode(3, OUTPUT); // GND ping
  digitalWrite(6, HIGH); // VCC +5V mode  
  digitalWrite(3, LOW);  // GND mode
  int sum_dist = 0;
  delay(2000);
//  for(int i=0;i<100;i++){
//    delay(50);
//    sum_dist += sonar.ping_cm();
//  }
//  usual_dist = sum_dist / 100;
  usual_dist = 164; // 167
  acc_dist = usual_dist;
}

void loop() {
  int dist = sonar.ping_cm();
  if(dist == 0){
    Serial.println("ZERO---------------------------------");
    delay(50);
    return;
  }
  Serial.print(dist);
  Serial.print('-');
  Serial.print(acc_dist);
  if(acc_dist < usual_dist){
    last_hit = millis();
//    Serial.print(acc_dist);
//    Serial.print('-');
//    Serial.print(usual_dist);
    Serial.print('S');
  }
  Serial.println();
  acc_dist = (acc_dist * 10 + dist)/11;
  if(millis() - last_hit < 6000){
    digitalWrite(A3, LOW);
  } else {
    digitalWrite(A3, HIGH);
  }
  delay(50);
}