Ultra Sonic range measurement module


Seeed ultrasonic sensor is non-contact distance measurement module, which is also compatible with electronic brick. It’s designed for easy modular project usage with industrial performance.


  • Detecting range: 3cm-4m
  • Best in 30 degree angle
  • Electronic brick compatible interface
  • 5VDC power supply
  • Breadboard friendly
  • Dual transducer
  • Arduino library ready


Supply voltage 5V
Global Current Consumption 15 mA
Ultrasonic Frequency 40k Hz
Maximal Range 400 cm
Minimal Range 3 cm
Resolution 1 cm
Trigger Pulse Width 10 μs
Outline Dimension 43x20x15 mm


Hardware Installation

A short ultrasonic pulse is transmitted at the time 0, reflected by an object. The senor receives this signal and converts it to an electric signal. The next pulse can be transmitted when the echo is faded away. This time period is called cycle period. The recommend cycle period should be no less than 50ms. If a 10μs width trigger pulse is sent to the signal pin, the Ultrasonic module will output eight 40kHz ultrasonic signal and detect the echo back. The measured distance is proportional to the echo pulse width and can be calculated by the formula above. If no obstacle is detected, the output pin will give a 38ms high level signal.


Includes important code snippet. Demo code like :

//    Function: Measure the distance to obstacles in front and print the distance
//              value to the serial terminal.The measured distance is from
//              the range 0 to 400cm(157 inches).
//    Hardware: Ultrasonic Range sensor
//    Arduino IDE: Arduino-1.0
//    Author:     LG
//    Date:      Jan 17,2013
//    Version: v1.0 modified by FrankieChu
//    by www.seeedstudio.com
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2.1 of the License, or (at your option) any later version.
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  Lesser General Public License for more details.
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#include "Arduino.h"
class Ultrasonic
    Ultrasonic(int pin);
    void DistanceMeasure(void);
    long microsecondsToCentimeters(void);
    long microsecondsToInches(void);
    int _pin;//pin number of Arduino that is connected with SIG pin of Ultrasonic Ranger.
    long duration;// the Pulse time received;
Ultrasonic::Ultrasonic(int pin)
    _pin = pin;
/*Begin the detection and get the pulse back signal*/
void Ultrasonic::DistanceMeasure(void)
    pinMode(_pin, OUTPUT);
    digitalWrite(_pin, LOW);
    digitalWrite(_pin, HIGH);
    duration = pulseIn(_pin,HIGH);
/*The measured distance from the range 0 to 400 Centimeters*/
long Ultrasonic::microsecondsToCentimeters(void)
    return duration/29/2;
/*The measured distance from the range 0 to 157 Inches*/
long Ultrasonic::microsecondsToInches(void)
    return duration/74/2;

Ultrasonic ultrasonic(7);
void setup()
void loop()
    long RangeInInches;
    long RangeInCentimeters;
    ultrasonic.DistanceMeasure();// get the current signal time;
    RangeInInches = ultrasonic.microsecondsToInches();//convert the time to inches;
    RangeInCentimeters = ultrasonic.microsecondsToCentimeters();//convert the time to centimeters
    Serial.println("The distance to obstacles in front is: ");
    Serial.print(RangeInInches);//0~157 inches
    Serial.println(" inch");
    Serial.println(" cm");

Help us make it better

Thank you for choosing Seeed. A couple of months ago we initiated a project to improve our documentation system. What you are looking at now is the first edition of the new documentation system. Comparing to the old one, here is the progresses that we made:

  • Replaced the old documentation system with a new one that was developed from Mkdocs, a more widely used and cooler tool to develop documentation system.
  • Integrated the documentation system with our official website, now you can go to Bazaar and other section like Forum and Community more conveniently.
  • Reviewed and rewrote documents for hundreds of products for the system’s first edition, and will continue migrate documents from old wiki to the new one.

An easy-to-use instruction is as important as the product itself. We are expecting this new system will improve your experience when using Seeed’s products. However since this is the first edition, there are still many things need to improve, if you have any suggestions or findings, you are most welcome to submit the amended version as our contributor or give us suggestions in the survey below, Please don’t forget to leave your email address so that we can reply.

Happy hacking