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Built-in project · Arduino Uno R3

Ultrasonic distance on pins 12 and 11, on an Arduino Uno

An HC-SR04 with TRIG on pin 12 and ECHO on pin 11: the SR04 library times the echo and prints the distance in centimeters once a second. The whole build, an Arduino Uno and 1 more part, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

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Ultrasonic distance on pins 12 and 11 · Arduino Uno R3live0.000 s 0.00x
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The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

The code

The firmware exactly as the editor opens it. Change a line there and press Run: it compiles in the browser.

sketch.ino · Arduino Uno R3
// Ultrasonic distance: an HC-SR04 with TRIG on pin 12 and ECHO on pin 11.
//
//   HC-SR04 VCC  -> 5V       HC-SR04 TRIG -> pin 12
//   HC-SR04 ECHO -> pin 11   HC-SR04 GND  -> GND
//
// The sensor sends eight pulses of 40 kHz sound when TRIG goes high for 10
// microseconds, then holds ECHO high until the sound comes back. Sound travels
// about 343 meters a second, so every 58 microseconds of echo is one
// centimeter there and back. The SR04 library does the timing and the sum.
//
// Note the order in the constructor: echo first, then trigger.
//
// Drag the slider on the sensor to move the obstacle nearer or farther.

#include "SR04.h"

const int TRIG_PIN = 12;
const int ECHO_PIN = 11;

SR04 sonar = SR04(ECHO_PIN, TRIG_PIN);

void setup() {
  Serial.begin(9600);
  Serial.println("Mokxi Uno: HC-SR04 on pins 12 (TRIG) and 11 (ECHO)");
}

void loop() {
  long cm = sonar.Distance();
  if (cm == 0) {
    Serial.println("nothing in range");
  } else {
    Serial.print(cm);
    Serial.println(" cm");
  }
  delay(1000);
}

Parts list

3 parts, plus the jumper wires. Every one is in the editor's parts bin.

How it is wired

4 connections, pin by pin, read from the circuit itself. Each line is one set of pins joined together, by a jumper wire or a breadboard strip.

  • Ground: Arduino Uno R3 pin GND; Ultrasonic ranger pin GND
  • Arduino Uno R3 pin 12; Ultrasonic ranger pin TRIG
  • Arduino Uno R3 pin 11; Ultrasonic ranger pin ECHO
  • Arduino Uno R3 pin 5V; Ultrasonic ranger pin VCC

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