เซ็นเซอร์วัดระยะ อัลตราโซนิคเซ็นเซอร์ 2 - 400 cm Ultrasonic Module HC-SR04

• Working voltage: DC 5 V
• Static current: 3 mA
• Working temperature: 0 ~ + 70 
• Output way: GPIO
• Induction Angle: Less than 15 
• Detection range: 2 cm to 4 m
• Detecting precision: 0.3 cm + 1%
• Sensor size: Approx. 45 x 20 x 1.6mm

/*
  HC-SR04 Ping distance sensor]
  VCC to arduino 5v GND to arduino GND
  Echo to Arduino pin 13 Trig to Arduino pin 12
  Red POS to Arduino pin 11
  Green POS to Arduino pin 10
  560 ohm resistor to both LED NEG and GRD power rail
  More info at: http://goo.gl/kJ8Gl
  Original code improvements to the Ping sketch sourced from Trollmaker.com
  Some code and wiring inspired by http://en.wikiversity.org/wiki/User:Dstaub/robotcar
*/

#define trigPin 13
#define echoPin 12
#define led 11
#define led2 10

void setup() {
 Serial.begin (9600);
 pinMode(trigPin, OUTPUT);
 pinMode(echoPin, INPUT);
 pinMode(led, OUTPUT);
 pinMode(led2, OUTPUT);
}

void loop() {
 long duration, distance;
 digitalWrite(trigPin, LOW);  // Added this line
 delayMicroseconds(2); // Added this line
 digitalWrite(trigPin, HIGH);
 //  delayMicroseconds(1000); - Removed this line
 delayMicroseconds(10); // Added this line
 digitalWrite(trigPin, LOW);
 duration = pulseIn(echoPin, HIGH);
 distance = (duration / 2) / 29.1;
 if (distance < 4) {  // This is where the LED On/Off happens
   digitalWrite(led, HIGH); // When the Red condition is met, the Green LED should turn off
   digitalWrite(led2, LOW);
 }
 else {
   digitalWrite(led, LOW);
   digitalWrite(led2, HIGH);
 }
 if (distance >= 200 || distance <= 0) {
   Serial.println("Out of range");
 }
 else {
   Serial.print(distance);
   Serial.println(" cm");
 }
 delay(500);
}