# Complete Guide for Ultrasonic Sensor HC-SR04 with Arduino

This article is a guide about the Ultrasonic Sensor HC-SR04. We’ll explain how it works, show you some of its features and share an Arduino project example you can follow to integrate into your projects. We provide a schematic diagram on how to wire the ultrasonic sensor and an example sketch with the Arduino.

### Description

The HC-SR04 ultrasonic sensor uses sonar to determine the distance to an object. This sensor reads from 2cm to 400cm (0.8inch to 157inch) with an accuracy of 0.3cm (0.1inches), which is good for most hobbyist projects. In addition, this particular module comes with ultrasonic transmitter and receiver modules.

The following picture shows the HC-SR04 ultrasonic sensor.

The next picture shows the other side of the sensor.

### Features

Here’s a list of some of the HC-SR04 ultrasonic sensor features and specs—for more information, you should consult the sensor’s datasheet:

• Power Supply :+5V DC
• Quiescent Current : <2mA
• Working Current: 15mA
• Effectual Angle: <15°
• Ranging Distance : 2cm – 400 cm/1″ – 13ft
• Resolution : 0.3 cm
• Measuring Angle: 30 degree
• Trigger Input Pulse width: 10uS TTL pulse
• Echo Output Signal: TTL pulse proportional to the distance range
• Dimension: 45mm x 20mm x 15mm

### How Does it Work?

The ultrasonic sensor uses sonar to determine the distance to an object. Here’s what happens:

1. The ultrasound transmitter (trig pin) emits a high-frequency sound (40 kHz).
2. The sound travels through the air. If it finds an object, it bounces back to the module.

The time between the transmission and reception of the signal allows us to calculate the distance to an object. This is possible because we know the sound’s velocity in the air. Here’s the formula:

``distance to an object = ((speed of sound in the air)*time)/2``
• speed of sound in the air at 20ºC (68ºF) = 343m/s

### HC-SR04 Ultrasonic Sensor Pinout

Here’s the pinout of the HC-SR04 Ultrasonic Sensor.

You can check the Ultrasonic Sensor HC-SR04 sensor on Maker Advisor to find the best price:

## Arduino with HC-SR04 Sensor

This sensor is very popular among Arduino tinkerers. So, here we provide an example of how to use the HC-SR04 ultrasonic sensor with the Arduino. In this project, the ultrasonic sensor reads and writes the distance to an object in the serial monitor.

The goal of this project is to help you understand how this sensor works. Then, you should be able to use this example in your own projects.

Parts Required

Here’s a list of the parts required to follow the next tutorial:

You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!

## Arduino with HC-SR04 Sensor Wiring

Follow the next schematic diagram to wire the HC-SR04 ultrasonic sensor to the Arduino.

The following table shows the connections you need to make:

## Code

``````/*
* created by Rui Santos, https://randomnerdtutorials.com
*
* Complete Guide for Ultrasonic Sensor HC-SR04
*
Ultrasonic sensor Pins:
VCC: +5VDC
Trig : Trigger (INPUT) - Pin11
Echo: Echo (OUTPUT) - Pin 12
GND: GND
*/

int trigPin = 11;    // Trigger
int echoPin = 12;    // Echo
long duration, cm, inches;

void setup() {
//Serial Port begin
Serial.begin (9600);
//Define inputs and outputs
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
}

void loop() {
// The sensor is triggered by a HIGH pulse of 10 or more microseconds.
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
digitalWrite(trigPin, LOW);
delayMicroseconds(5);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

// Read the signal from the sensor: a HIGH pulse whose
// duration is the time (in microseconds) from the sending
// of the ping to the reception of its echo off of an object.
pinMode(echoPin, INPUT);
duration = pulseIn(echoPin, HIGH);

// Convert the time into a distance
cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343
inches = (duration/2) / 74;   // Divide by 74 or multiply by 0.0135

Serial.print(inches);
Serial.print("in, ");
Serial.print(cm);
Serial.print("cm");
Serial.println();

delay(250);
}
``````

View raw code

### How the Code Works

First, you create variables for the trigger and echo pin called trigPin and echoPin, respectively. The trigger pin is connected to digital Pin 11, and the echo pin is connected to Pin 12:

``````int trigPin = 11;
int echoPin = 12;``````

You also create three variables of type long: duration and inches. The duration variable saves the time between the emission and reception of the signal. The cm variable will save the distance in centimeters, and the inches variable will save the distance in inches.

``long duration, cm, inches;``

In the setup(), initialize the serial port at a baud rate of 9600, and set the trigger pin as an OUTPUT and the echo pin as an INPUT.

``````//Serial Port begin
Serial.begin (9600);
//Define inputs and outputs
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);``````

In the loop(), trigger the sensor by sending a HIGH pulse of 10 microseconds. But, before that, give a short LOW pulse to ensure you’ll get a clean HIGH pulse:

``````digitalWrite(trigPin, LOW);
delayMicroseconds(5);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);``````

We use the pulseIn() function to get the sound wave travel time:

``duration = pulseIn(echoPin, HIGH);``

The pulseIn() function reads a HIGH or a LOW pulse on a pin. It accepts as arguments the pin and the state of the pulse (either HIGH or LOW). It returns the length of the pulse in microseconds. The pulse length corresponds to the time it took to travel to the object plus the time traveled on the way back.

Then, we calculate the distance to an object, taking into account the sound speed.

```distance = (traveltime/2) x speed of sound

The speed of sound is: 343m/s = 0.0343 cm/uS = 1/29.1 cm/uS

Or in inches: 13503.9in/s = 0.0135in/uS = 1/74in/uS```

We need to divide the travel time by 2 because we have to consider that the wave was sent, hit the object, and then returned to the sensor.

``````cm = (duration/2) / 29.1;
inches = (duration/2) / 74;``````

Finally, we print the results in the Serial Monitor:

``````Serial.print(inches);
Serial.print("in, ");
Serial.print(cm);
Serial.print("cm");
Serial.println();``````

## Source code with NewPing Library

After installing the NewPing library, you can upload the code provided below.

``````/*
* Posted on https://randomnerdtutorials.com
* created by http://playground.arduino.cc/Code/NewPing
*/

#include <NewPing.h>

#define TRIGGER_PIN 11
#define ECHO_PIN 12
#define MAX_DISTANCE 200

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

void setup() {
Serial.begin(9600);
}

void loop() {
delay(50);
unsigned int distance = sonar.ping_cm();
Serial.print(distance);
Serial.println("cm");
}
``````

View raw code

### How the Code Works

Getting the distance to an object using the NewPing library is much simpler.

You start by including the NewPing library:

``#include <NewPing.h>``

Then, define the trigger and echo pin. The trigger pin is connected to the Arduino digital Pin 11 and the echo to Pin 12. You also need to define the MAX_DISTANCE variable to be able to use the library.

``````#define TRIGGER_PIN 11
#define ECHO_PIN 12
#define MAX_DISTANCE 200``````

Then, you create a NewPing instance called sonar:

``NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE);``

In the setup(), you initialize the Serial communication at a baud rate of 9600.

``Serial.begin(9600);``

Finally, in the loop(), you just need to use the ping_cm() method on the sonar object to get the distance in centimeters.

``unsigned int distance = sonar.ping_cm();``

If you want to get the distance in inches, you can use sonar.ping_in() instead.

## Demonstration

Upload the code to your Arduino board. Then, open the Serial Monitor at a baud rate of 115200.

The distance to the nearest object is printed in the Serial Monitor window.

## Wrapping Up

In this post, we’ve shown you how the HC-SR04 ultrasonic sensor works and how you can use it with the Arduino board. For a project example, you can build a Parking Sensor with LEDs and a buzzer.

If you are a beginner to the Arduino, we recommend following our Arduino Mini-Course that will help you get started quickly with this amazing board.

If you like Arduino, you may also like:

You can find all our Arduino projects and tutorials here.

We hope you found this tutorial useful. Thanks for reading.

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### 147 thoughts on “Complete Guide for Ultrasonic Sensor HC-SR04 with Arduino”

1. Hi, Thanks for your interesting and informative projects.

• Thanks Robert for your feedback.
I’m really glad you found this information useful!
Thanks again,
Rui Santos

• Can u plzz tell me the procedure to make a drone at home

• I intend to create a tutorial like that in the future, but right now I don’t have any tutorial on that subject.

• Hello, I want to that sensor in Drone, It is possible?

• Hello all, just got my first arduino, and i have this working. but for my project i need a second ultrasonic sensor. and i have no idea how to do that.
ive added a triggerpin and an echo pin in the code for the second sensor, but how do i define to the code there are 2 sensors? do i need to copy the whole code again for the second sensor? or can the code run for both at the same time?

• Where you see number that I add number ‘2’, this is for the second sensor.

int trigPin = 11; // Trigger
int echoPin = 12; // Echo
int trigPin2 = 9; // Trigger for second sensor
int echoPin2 = 10; // Echo for second sensor
long duration, cm, inches;
long duration2, cm2, inches2;

void setup() {
//Serial Port begin
Serial.begin (9600);
//Define inputs and outputs
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(trigPin2, OUTPUT);
pinMode(echoPin2, INPUT);
}

void loop() {
// The sensor is triggered by a HIGH pulse of 10 or more microseconds.
// Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
digitalWrite(trigPin, LOW);
digitalWrite(trigPin2, LOW);
delayMicroseconds(5);
digitalWrite(trigPin, HIGH);
digitalWrite(trigPin2, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
digitalWrite(trigPin2, LOW);
// Read the signal from the sensor: a HIGH pulse whose
// duration is the time (in microseconds) from the sending
// of the ping to the reception of its echo off of an object.
pinMode(echoPin, INPUT);
pinMode(echoPin2, INPUT);
duration = pulseIn(echoPin, HIGH);
duration = pulseIn(echoPin2, HIGH);
// Convert the time into a distance
cm = (duration/2) / 29.1; // Divide by 29.1 or multiply by 0.0343
cm2 = (duration/2) / 29.1;
inches = (duration/2) / 74; // Divide by 74 or multiply by 0.0135 // Divide by 29.1 or multiply by 0.0343
inches2 = (duration/2) / 74;
Serial.print(inches);
Serial.print(“in, “);
Serial.print(cm);
Serial.print(“cm”);
Serial.println();
Serial.print(inches2);
Serial.print(“in2, “);
Serial.print(cm2);
Serial.print(“cm2”);
Serial.println();

delay(250);
}

• its a great project!! i connected there a GSM module, and it sends sms when its less than 15cm
AND IT WORKED !!

2. Hi, this is to me really helpful. Now I able to understand better how HC-SC04 work.. Hopefully you will keep on sharing this valuable knowledge.
Thank you very much ^_^

• Thanks Abdul!
I’ll try my best to create content every week.

See you in the next project,
Rui Santos

3. make simple if use NewPing library.

the code like this .

#include

#define TRIGGER_PIN 12
#define ECHO_PIN 11
#define MAX_DISTANCE 200

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

void setup() {
Serial.begin(9600);
}

void loop() {
delay(50);
unsigned int uS = sonar.ping_cm();
Serial.print(uS);
Serial.println(“cm”);
}

• yeah I’ve mentioned that library in the notes.

It’s a really nice library specially when your working with robotics and using this sensor.

Thanks for sharing Iman!

• I’ve added that example to my blog post!
Thanks for sharing!

Have a nice day,
Rui

• hi rui , can we become friends , i am interested in robotics can u guide me , i m waiting………..

• Thanks for this code! There is actually a small mistake in the code using the Ping library: pin 11 and 12 should be swapped to work with the wiring you are showing,

• Thank you for letting me know! I’ll fix that!

4. Unfortunately you missed out the one thing that gives people trouble.
If the HC-SR04 does not receive an echo then the output never goes low.
Devantec and Parallax sensors time out after 36ms and I think 28ms respectively. If you use Pulsin as above then with no return echo the program will hang for 1 second which is the default timeout for Pulsin. You need to use the timeout parameter.
http://arduino.cc/en/Reference/PulseIn
The HC-SR04 barely works to 10 feet giving a total path length of 20 feet and a path time of about 20ms so set the timeout to something above that, say 25 or 30ms.
If you put a resistor, say 2k2 between E and T then only connect to T you can use the HC-SR04 from just one Arduino pin. Look up single pin operation of ultrasonic sensors.
Also if you are using a HC-SR04 with a PicAxe you need to up the clockspeed to at least 8MHz otherwise they don’t see the start of the echo pulse so pulsin never starts. The HC-SR04 works fine with a BS2.

• Hi David,
I totally forgot that and some problems I wasn’t aware of.
Next weekend I’ll try to update this post and add all those notes.

Thanks for such a detailed comment and for improving my content!

thanks again,
Rui santos

• Hi David,
You really explained well some stuff that I wasn’t aware of.

I hope you don’t mind.

Have a nice day,
Rui

5. Hi,

very cool guide. Thanks for that! If you want to see a “real life example”, please have look on my blog: danimathblog.wordpress.com/tag/spider/

best regards
Andreas

• Hi Andreas,
All the best,
Rui Santos

6. Fala amigo, beleza?
Testando seu codigo esbarrei em um problema, quanto mais proximo um objeto do sensor, mais rapido o programa faz seu loop, achei isso muito estranho pois na ultima linha o “delayMicroseconds(300)” define basicamente que o loop sera dado a cada 300milisegundos (logico um pouco mais pq tem outros pequenos delays e tem o tempo de processamento), mas nao sei pq o loop fica mt acelerado, acho que ate a baixo de 300milisegundos.
Como o meu programa depende desse tempo, basicamente é um buzzer que almenta a frequencia de apitos com a proximidade de um objeto, nao funcionou com seu codigo. Porem usando a biblioteca NewPing, e usando como base o codigo exemplo que o Imam postou esse erro foi resolvido. Sabe me explicar o porque?

• Olá Rodrigo,
realmente é um erro um pouco estranho. Eu vou testar isso agora mesmo e tentar resolver.

assim que consiga resolver altero este post.
Pode sempre usar a biblioteca NewPing. É mesmo muito boa e simplifica imenso o nosso trabalho.

Abraço,
Rui

• Olá Rodrigo,
já resolvi o problema esqueci-me de fazer low ao trigPin no inicio do loop:

digitalWrite(trigPin, LOW);
delayMicroseconds(5);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);

E isso estava a fazer com que o sensor se comporta-se de uma forma estranha. Já está resolvido.

Abraço,
Rui

7. is it possible that arduino uno can accomodate 4 ultrasonic sensors?

• yes the Arduino can easily accomodate 4 ultrasonic sensors.
Each sensor only requires 2 digitals pins. (4 ultrasonic sensors * 2 digital pins = 8)
so you still have some pins left.

But you need to right a good code so they don’t conflict with each other!

8. I glad of your work, but i want to know the internal working of the module. It consist of 3 ICs . I want to know the Working of them. Can you help me?

• Look on Devantec’s site, he invented and published the circuit and code

i have a question about the sensor . after one trigger does it continue to measure the distance , i mean if we want it to measure the distance for some time , do we need to send the trigger signal continuously?

• Hi Ali,
when you send the trigger after a few seconds you need to read that signal with the echo to see how much time it took the ultrasonic wave to touch the nearest object.
So that means you need to keep repeating that process over and over again to measure the distance…

10. I have six of these…
before connecting to the micro controller, all of them put 5v on trig at power on. is this the correct behavior?
I understand that the micro controller is to put 5v on trig for 10us to trigger the pulse… can you explain how it can be correct to put 5v on trig as instructed, when 5v is already on trig on power up (without connecting to anything)?

nice job with this write up… thanks

• The microcontroller puts 5V on the trigPin when you turn the digital pin of your Arduino to HIGH.

When you do this digitalWrite(trigPin, HIGH);

• Input pins when not connected to anything are said to float and because the input impedance of them is high they can be affected by stray electrostatic voltages on anything, including your fingers. Hence voltage on them can be at an illegal value between the thresholds for logic 0 and logic 1 which can cause the internal circuitry to fail or lock up or generally do bad things. To avoid this a lot of input pins have either pull-up or pull-down resistors connected to them so that when the pin is not connected it will be in a known state.
The Trig pin has a 10K pull up resistor connected between it and Vcc, on mine you can see the tiny surface mount 103 resistor on the back of the board by the header pins. So when the board is powered and no circuitry is connected to Trig the voltage on it will be at Vcc.
The control computer must first set the pin to logic zero and then, when it wants to trigger the HC-04, set the pin to high for 10us before setting it low again.

• im yannay and im proude

• ha a same question i hope u may help me out
i have even not connected the trig pin to the arduino and only the echo is connected but even though i am getting the echo valuse can u please justify this to me

11. I have a problem… I also have the “OUT” pin…
how can I program arduino ?

12. Thank you man!!

• You’re welcome!

Is there any way to make sure sensor is working or not?

• You can see what’s happening with the sensor with an Oscilloscope.
But if you followed my tutorial and it’s not working for you, your ultrasonic sensor might be damaged.

• Thanks for reply. Yes it seems my ultrasonic sensor is not working.

I had change it and everything gone well.

• Awesome Abdo!
I’m glad it’s now working for you

• The sensors are cheap enough so the easy way to see if a sensor is working is to try another one. I have used maybe 20 of them without any problems until the other day when one stopped working. I swapped it and the replacement worked. Nothing was obviously wrong with the bad sensor but if I held it, it started working again so I resoldered the joints on the two transducer cans and the connector and now it works again.

14. Hey this is really useful stuff!

I was wondering if you have ever used the Ultrasonic sensor to control a music shield? Im currently attempting this project and want the song to change depending on how far away you are from the sensor, just using 2 songs though.
Any help will be muchly appreciated!

Lorna

15. hi
i don<t know how to test hcsr04 sensor good or not

16. thanx a lot for this info. But I need your help,I am expecting reading from sensors in millimeters. Is it possible to have??

• Hi Sidd,
You can simply change my code to do the conversion to millimeters by multiplying the centimeters output.

• There are ten millimtres in one centimetre, multiply the centimetre reading by 10

17. I’ve tried a number of different sketches with my HC-SR04 and always have the same problem. Once the maximum range of the sensor is reached, a distance of zero is returned and then the sensor will not start working again. Once it has stopped I can move objects in front of it (like my hand) but continue to get no distance readings. It works fine until then, though. I realize no one has commented here recently, but if anyone has any idea what my problem is, please let me know. Maybe a defective sensor?

• Sam
I have never had that problem. Can you post the sketches you have tried then I can test it with my HC-SR04s. I have them from several different manufacturers. Maybe yours is faulty.
David

• I have also had this problem with cheap HCSR04 modules I got from aliexpress (\$1 each oh well!). Once an “out of range” reading occurs, the device never works again, the output from echo just stays high all the time until you power it down and back up.

I am looking for a solution too and have tried quite a few things including hardware and software with no luck so I feel like the reason they were a buck each was that they are simply defective “seconds” with some hardware flaw.

But if anyone has any insights on this I would appreciate hearing about it.

• 4 out of 5 modules have the same problem. They work for a while. Then when I lay my breadboard on a flat surface, the modules stop reading. I can audibly hear a “tick tick tick” coming from the cans while it works. When it stops working the sound stops. I’ve found that if I blow on the can, the module resumea working again. Or I can flick it with my finger and it will resume. Odd.. has anyone else seen this issue?

• I am ordered over 100 of these sensors for a class, and well over 75% have this issue, regardless of which code, library, or timing I am using. A previous set of 100+ ordered last year do not have this issue, and the ticking cannot be heard.
Flicking it or resetting the power seems to fix the problem until I max out the range or change distance quickly again.
Did you find a solution or cause to the issue?

• Sam,

I have encountered the same issue. I ordered three sensors, one of which performs as it should, one is completely DOA, and the third behaves as you describe. I have found that it will start working again if I clap my hands or snap my fingers near the sensor. It will then work for a while but will eventually hang again. I have been searching the web for a programatic way of correcting it, but haven’t found an easy way. The closest I have found is the last post at:

18. I have the same problem that Sam Khoury has. Once in a while the sensor goes into a mode where the echo pulse is very sharp indicating almost zero distance and the only way to recover from this is to disconnect the sensor and reconnect it. I also found that when the repetition of trigger is faster than 700ms this type of problem crops up. Presently I use a repetition interval of 3 to 4seconds.

19. I wrote my own tutorial based on this sensor and a Servo Motor. Your tutorial was very helpful in accomplishing that, so if you have time, I would appreciate your feedback: Arduino Servo Sweet Tutorial

20. Olá Rui.
Digamos que eu queira colocar o trigger e o pin nas saidas analógicas do Arduino.
Eu teria que colocar TRIGGER_PIN A4 e ECHO_PIN A5?

21. When you convert the input time to cm you use 29.1 and 74 for in. I was wondering were these numbers come from.

• They are the conversion factors for the speed of sound, to converet the time – for the sound to go out, hit the target and return – to distance

22. Hello, I want to use this sensor on my drone. It is possible in outdoor?

23. Some knock-off models of the HC-SR04 do not implement a timeout if no echo is detected at all. In that case, the echo pin will simply remain high forever and will not generate any new pings, regardless of what you do with the trigger pin. The original model from Robot Electronics times out after 36 ms and does not have this problem, but many (all?) cheap knock-off models do.

You can reproduce the problem easily by covering the receiver transducer with your thumb, then removing your thumb. If your sensor doesn’t have a timeout, it will stop generating pings and the only way to recover is to power cycle the sensor.

A workaround that works for me so far is to test the state of the echo pin 100 ms after triggering a ping. If it’s still high, you’re in a stuck state. If you wire power to the sensor through a transistor and control that transistor via another pin, then you can power cycle the sensor via software and get back to a working state.

• I think I was the first person to point out that the HC-SR04 doesn’t time out if it doesn’t receive an echo unlike the SRF04 from Robot Electronics.
I have used a lot of the HC-SR04 modules from different manufacturers in China and non of them have needed power-cycling if they don’t receive an echo. Always a new trigger pulse results in a new ping being sent.
It is possible if you try to use them on a single uController pin by wiring Echo and Trigger together that they will lock up, however you should never wire them like that since the the uController pin when set to output to trigger the module will fight with the Echo pin (an output) and could damage both the HC-SRF04 and the uController.
If you connect the Echo and Trigger pins through a 2k2 resistor and connect the uController pin to the Trigger pin (not the Echo pin) then the 2k2 resistor stops the pins fighting and you can use a single uController pin without any problems.

• I can confirm without a doubt that some of the very cheap (I’m talking about 80 cents including shipping!) units do lock up even if you use both trigger and echo on different controller pins. I can also confirm that putting a 2k2 resistor between trigger and echo to run in 1 pin mode doesn’t help (wouldn’t expect it to since 2 controller pin mode doesn’t).

They are not even consistent. i bought 10 of the 80 cent modules and 5 of them are very, very unstable and lock up very easily. Others only lock up occasionally. Another oddity (that others have also pointed out) is that sometimes if they lock up if you touch them with your finger they unlock, or even if you snap your fingers close to them. Apparently this finally triggers the sensor to sense a ping.

I upgraded to \$2 devices from itead studio and they work great. They do have a 36 millisecond timeout built in and I’ve used 5 different units from them with no problems.

• Well I have used maybe 30 from 6 different batches with different PCBs and have yet to have one that locks up.
My understanding is that the HC-SR04 was designed for a bicycle alarm where it is a good thing if nobody is near and hence no echo , so it makes no sense for them to lock up.
There is always the possibility that if the Trigger pin floats because the uController pin connected to it has been made an input then the module will be susceptible to static – ie the approach of fingers. Correcting the software or using a 10k pull down would stop that.

24. Hi,
Thank you for the article. It is great!
Can anyone please tell me, can i use this sensor 100 meters apart from arduino connected via wires.

• I’m not sure if you can… If it would lower the signal quality too much.

• Murtaza – of course you can’t, it is just basic electronics, it is like asking “can I get a 100m USB lead?” or will my phone work underwater?”. 100m of wire has too much inductance, resistance and capacitance for a signal from the Arduino to reach the sensor or for a reply from the sensor to reach the Arduino. You could do it with two Arduinos and a radio link between them and the HC-SR04 connected by short wires to one of them, or the two Arduinos could be connected using RS485 communication shields and 100m of suitable cable.

25. Hi Rui,

I just got the idea to take the last 10 distance results in a global queue variable to detect if my bot is moving at all (maybe it ran onto an “invisible” obstacle). I used the standard deviation of the distance array for that and although i have quite different results every time i measure i found 1cm enough to detect if i’m stuck in about 1 – 5 seconds.

Maybe this will work out for others, too.

Do you have a method for improving the quality of measurements?
I found this one but seems complex to me:
ijcte.org/papers/118-G227.pdf

Would you agree to take the standard deviation for that?

Do you have a much better approach for motion sensing?

Kind regards, Bernd

26. Hi David,
I can also confirm, waht was said about the cheap HC-SR04. It locks up very fast and can only be resetted by power off/on.
Mine also shows the effect described before, like when you cover the sensor with your finger, its stops immediately. Bought 10 of these and tested 2 so far, both are behaving the same. Seems to be just crap from china. Should have bought the real ones.
Have tested it with 5 different scripts, motor shield v1 and v2, but it all comes down to the sensor failing.
Cheers, Matthias

• The ones from iTead Studio are about \$2 each and they work reliably for me every time.

If you buy the ones that are like \$1 each, well, you get what you pay for. Some of them work and some don’t. I think it just depends on what batch you get.

27. Marza,
Regarding: Can anyone please tell me, can i use this sensor 100 meters apart from arduino connected via wires.

Maybe.
Here are things to consider. The cable adds capacitance. For CAT5 cable the capacitance per foot might be 52pF/meter so you have 5200 pF loading on the I/O lines. It may be a problem, but I doubt it. Assuming the output impedance (driving resistance) of the I/O pins is as high as 1K Ohm , then the time constant of the I/O signals (the product of the R and the C) is about 1×10^3 x 5200*10^-12 = 5.2 x 10 ^-5. Or 0.052 mS.
This will make an unmeasurebly small error.

Now the long wires themselves add a litter resistance. It is less than 0.2 ohms / meter so for 100 meter it is <20 ohms. Again not important when the I/O pins "impedance" (which is like resistance) is already probably 1K ohm.

The only problem with long wires is they become antennas for stray signals and pickup of induced surges from lightning. So it may work fine until one day lighting ruins it all.

I hope this helps and if you try it let us know.

28. Great turtorial! This got me really starting on using my Arduino more.

29. help it shuts down when i do that!

30. Hey! I found it totally useful and interesting! But i have got a question… This may sound totally stupid amd weird… Can I just connect an ultrasonic sensor to a buzzer and them use it for object detection? I mean… Is the arduino that important… Can’t there be a simple circuit?
Hope i’ll get my answer…. Thanks

• The Arduino is what talks with the ultrasonic sensor and reads its proximity

• What i actually want to make is a smart blind walking stick.. Someone told me that the arduino has to be connected to the pc for the ultrasonic sensor to work… But if i keep it connected, then i can’t move my stick?…. Yea, i know i am totally stupid and i know nothing about these sensors… But could you help me out here sir?

31. Hey…what i actually want to make is a smart blind walking stick with an ultrasonic sensor…. Someone told me that the arduino has to be connect to the pc for the ultrasonic sensor to work… So if i hav to keep the arduino connected, then i can’t move my stick?… I know i am stupid and j know nothing about these sensors… Could you please help me out here sir?

• I don’t have any tutorials on that exact subject, but thank you for asking,
Rui

• You need to learn about electronics, microcontrollers (the Arduino is a microcontroller) and programming/software otherwise you won’t understand the answers. There are plenty of tutorials on the web for electronics and programming the Arduino.

• The arduino does the calculation for the distance. If you just use the echo pin, it will be outputting a high on every echo irrespective of the distance. That may not give you any distance based control but your alarm device may get continuously triggered irrespective of distance.

• You probably ought to buy an Arduino Uno and an Ultrasonic sensor and then work through the examples here. You will find that you only need the PC connected for programming the Arduino or for displaying the distance measurement, (if that is what you want to do).

32. nice one can u guide me through more rojects using hc sr04 and arduino UNO

33. Thanks for this tutorial! This was really helpful for me while I was getting started.

• You’re welcome!

34. Im trying to activate my car (hrc-sr04) but i cant seem to get it working do you have any other advice im 12 so make it simple

• What device are you referring?

35. Hi, would anyone be able to tell me how the distance is actually calculated. Everywhere I look, the value of 58.2 shows up, and in this example that has been halved as the distance value hasn’t been. I know that the distance needs to be halved as we are measuring the distance for the wave to hit an object not hit an object and bounce back, but this number just appears with no explanation anywhere?

• Sounds like your sensor is broken or there’s a connection wrong..

36. How do I use this sensor in the gsm and gps based project to monitor the level of waste in the bin?

• I don’t have any tutorials on that exact subject.

Rui

37. What if reciver is also detecting the obsticles??? Then its a problem if sensor or may be of coding??

• It might be a problem with your wiring or the sensor

38. I’m very interested in these type of projects.

39. really glad you found this information useful!

Regards
Bharatam

• You’re welcome!

40. Hi, Thanks for your interesting and informative projects.

• You’re welcome! 🙂

41. Hello sir i have a question how can i measure the human height if the wave never reflected because of our hair?

• The ultrasonic sensor waves should find the hair as an obstacle and come back..

• Hair will most likely scatter and absorb the sound wave unless the receiver is quite close, you will have to experiment. Then again what do you mean by height of the person? Do you mean to the top of their head or the top of their hair, reading off the top of their hair would in lots of cases be meaningless. Think about what you are doing.

42. Thanks for the Tutorial! but I don’t understand why mine doesn’t work. The Serial monitor shows a constant value (that feels like random and not the actual distance). When I touch the USB connector, the value shows “0in, 0cm” (infact, touching some metal surface of the arduino or of the Ultrasonic sensor leads to this result). Is this some kind of grounding issue? Is there a way to fix this? Is any one of the component bricked? Thank you in advance.

• Hi.
If the tutorial is not working, it may be because of some of the following reasons:
– your ultrasonic sensor is faulty – you need to get a new one;
– the wiring is not correct – double-check the wiring using the schematic diagram provided;
– also make sure you have selected the right baud rate on the Serial Monitor.
I hope this helps.
Regards,
Sara 🙂

43. Its really a great information , it will really helpful for beginner Thank You

44. really appreciated your free E books thanks for taking the time to give out this information

• Thank you! 🙂

45. My HCSR04 ultarsonic sensor is not working properly.. with no object in front of sensor. The circuit is working… which I don’t want.
What to Doo..?

• Hi.
What do you mean by “not working properly”. Can you provide more details?
Are you getting any errors on your serial monitor?
Regards,
Sara

46. Do you know how to implement it with MicroPython?

• Hi Sabine.
We don’t have any tutorial for what you are looking for.
But there are several libraries for MicroPython that you can use for ultrasonic sensor, for example:
github.com/rsc1975/micropython-hcsr04
I hope this helps.
Regards,
Sara

47. It is very good

• Thanks 🙂

48. Hi,
I am using ultrasonic sensor to classification of milk based on viscosity. So for that i want the code so please help me
condition:
If range is between 0cm to 4cm then display viscosity is high
If range is between 4cm to 7cm then display viscosity is medium
If range is between 7cm to 10cm then display viscosity is low.

49. HI! Sara Santos
can we place acrylic clear sheet of 2mm in front of the sensor and mount for making it waterproof and get the level of the water?

Please suggest, we are planning to make some application; where the sensor has to be placed inside the water container and it should not be visible by anybody when the container cap is open and if by chance the container falls down or kept upside down by mistake the sensor should not get damaged by water spill over it.

Please let us know, so we can make an enclosure and give a slot cut with acrylic clear glass of 2mm mounted in front of the sensor for getting the accurate water level.

Thank You.
Darshan

• Hi Darshan.
This ultrasonic sensor was made to work when the signal is transmitted on air.
I think that if you try to cover it with an acrylic glass, it will interfere with your results and you won’t have accurate measurements.
However, take a look at this discussion in the Arduino forum and see if something can help with your project: forum.arduino.cc/index.php?topic=349192.0
Regards,
Sara

50. I am having a problem as it is showing only 0 in both the codes what to do ?

• Hi.
What exactly do you get in your serial monitor?
Regards,
Sara

51. Hai sir, I have interfaced ultrasonic sensor with Arduino using serial monitor. Now, I want to interface LCD to monitor the distance values could you please provide the schematic to interface LCD with Arduino.
I have purchased the ultrasonic sensor
uitechies.co.in/BBBcircuits/product.php?product=ultrasonic-range-finder-module-sensor-distance-measuring-transducer

52. Are we supposed to use a screen?
Where does the output gets displayed.. I’m new to this I did the wiring as you’ve shown and typed the code similarly but I don’t understand what’s supposed to happen next… It’s doing absolutely nothing… Am I missing out of something too obvious? Sorry I’m a newbie with Arduinos

• Hi.
With the Arduino connected to your computer, open the Arduino IDE Serial Monitor (magnifying glass icon at the top right corner) and you should start seeing the distance of obstacles to the sensor.
Regards,
Sara

53. hey, im getting zero always, what can i do?whats my problem?

• Can you try with a different Ultrasonic sensor? Unfortunately these cheap sensors sometimes are broken and using a new one fixes the issue.

54. Hello Santos family,

I have noticed the Arduino IDE is very often used in your projects.
For experienced users is that no problem, however when you are not that familiar with programming it could be very frustrating to get things work properly.

I found another way to resolve this in the ESP Easy (mega) flasher Tool.
I use the Wemos D1 mini shields to stack compact solutions together.
It is in combination with Domoticz (for reporting) a fine combination of Tools.

What I noticed with the Ultra Sonic Range finder is that it will not work with Wemos D1 Mini (ESP8266 System on Chip (SOC)) but when connected to a NodeMCU Develop SOC it works instantly.

Is it possible to tell if there is a significant difference between the SOC for the Wemos D1 mini and the NodeMCU Dev SOC?
Or is this a classic situation of comparing Appels and Peers? (Dutch expression).

Would be nice if it is possible for you comment on this.

Best regards
Arjen
Netherlands

55. Hi! is it possible to use hc-sr04 to trigger the button in php?

56. Lots of great comments and it may be covered already but so many to look up I thought I’d just ask.
I want to measure the water level of a small cylinder tank.
What would I need to change or add to the code to get it to read in milliliters.
TIA

57. You would have to know the surface area of the tank so you could convert surface rise or fall to volume change. [millimetres=distance, millilitres=volume]

• Yes. The Diameter is 15cm so the surface area is A=Pi R2 so 176.7…
so how would I put that in the code.

• 1 – Research how to calculate the area of a circle in centimetres
2 – Research how to calculate the volume of a cylinder in cubic centimetres
3 – Research the volume of a millilitre in cubic centimetres
Then get back to me.

58. i have attached a buzzer & the problem is when water level reaches 100% sensor value goes 100% then 99% for few times this is due to water is pumping to the tank, so the buzzer also act accordingly. is there any way to correct this issue?

59. I know this is a very old thread but for correctness I note at the Top you show

Pins
VCC: +5VDC
Trig : Trigger (INPUT)
Echo: Echo (OUTPUT)
GND: GND

``` pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); ```

Could be confusing to some?
Clearly your “PINS” description is inverted.

Cheers
Ralph

• Only confusing to those who don’t understand ‘input’ and ‘output’
The HC-SR04 Trigger pin is marked INPUT because it is an INPUT pin which receives the trigger pulse, and the Echo pin is marked OUTPUT because it outputs the return pulse which gives the distance.
The Sketch has pinMode(trigPin, OUTPUT);
because that pin is connected to the HC-SR04 Trigger pin and on the Arduino it has to be set to OUTPUT so it can generate the trigger pulse to the HC-SR04.
The Sketch has pinMode(echoPin, INPUT);
because that pin is connected to the HC-SR04 Echo pin and on the Arduino it has to be set to INPUT so it can receive the trigger pulse from the HC-SR04.

Try it out, change the sketch to what you think is right and you will find nothing works and then probably blame the Chinese HC-SR04 as being faulty.

60. is it possible to interchange the trig and echo pins. what i want to do is to transmit on one transducer and receive on the other, thereafter transmit on the second and receive on the first

61. hi, it is really helpful to understand the coupling of the sensor with the Arduino.
I need some info. i am intending to connect 5 ultrasonic sensors in my project. Then how should i connect the Trig and Echo pins. either i should mutually join all respective wires of all five sensors and then connect the wires to the arduino digital pins, or i should connect the trig and echo pins of all five sensors to connect in the arduino, separately.
hope you will hear from me soon.

• Hi.
You should connect them to separate pins. Otherwise, you won’t know to which sensors the measurements correspond.
Regards,
Sara

62. If you want to try project with visualisation of data at remote webserver where ESP will send datas, you can use mine project: arduino.clanweb.eu/studna_s_prekladom/?lang=en It is free to use at test web interface. You can also read datas from website by using JSON client that can parse datas. So you can integrate height of water level and its volume to your home automatication – Hassio / Domoticz / Loxone.

63. the 3mm accuracy is theoretical only , in practice it can be as bad as 10cm !!q

64. I have had many problems getting the Ultra Sonic sensor to work in combination with servo motors and/or encoder motors. From my experience and from what I have read they all use the same timer and with more than one device the timer(s) get confused which pulse they are timing. Random, jerky and erratic movements result ruining the entire project. Seems like a bad design to me. Is there a solution to this?

• The bad design is using Arduino libraries when you have no idea whether they use the same Arduino resources or not. I have used lots and lots of servos and lots of the HC-SR04 on Arduinos without any problems because I gave up using Arduino libraries from the beginning after discovering that the IR library causes the servo library pulses to be way off as well as being useless for receiving IR commands. Unless they have changed the design of the HC-SR04 recently you must use the pulsein timout – pulseIn(pin, value, timeout) in case the HC-SR04 does not see anything, otherwise the code waits for the default pulseIn() timeout which is 1 second according to the Arduino documentation. I use 20,000 for 20ms timeout which corresponds to about 10 foot which is more than the HC-SR04’s useful range.

65. situation : assuming blind person is in problem when buzzer beeps using ultrasonic sensor( range 50 cm ) then he presses a button which is connected to his stick . after pressing button , a msge must be sent ( using gsm module ) to certain phone number saying ” i am in danger ” . and with this msg , is live location ( using gps module )must be sent to that same number.. ( location in terms of latitude and longitude) i need answer in c/c++ sim900a

• Hi.
You can check the following tutorials with the SIM900:
https://randomnerdtutorials.com/?s=SIM900
At the moment, we don’t have any GPS examples with the SIM900. But there are several libraries with examples.
Regards,
Sara

66. Hi! thanks in advance. i would like to know if it possible to control volume of a mp3 file just by distance. so when i get close to de HC-SR04 the volume turns up, and when i get far the volume goes down.

thanks!