Arduino Hall Effect Sensor Tutorial: The Easy Way

 

Arduino Hall Effect Sensor Tutorial DIY Hacking

Arduino Hall Effect Sensor Tutorial

Have you ever wanted to make a project that involved contact-less sensing. For example: to detect a door close, to count the number of revolutions of a wheel or even to make a speedometer? Then this Arduino Hall Effect sensor tutorial is for you.

This project uses a hall effect sensor to detect the presence of a magnet. Whenever a magnet moves past this sensor, it can detect it.  Hence, this sort of sensor can be used to do a lot of things. For instance, if we need to detect a door close; then we simply have to attach a magnet to the door and a hall sensor to the frame of the door. Whenever the door closes, the magnet gets placed near the hall effect sensor and therefore we are able to detect that the door has been closed.

Similarly, this same principle can be used to make a speedometer for a bike or any other vehicle. If a magnet is attached to the wheel and a hall effect sensor is placed somewhere in the frame of the bike, the time taken for the wheel to complete one revolution can be achieved. Thus, using a bit more math, we can detect the speed of movement of the bike.

What are the stuff required to do this project? Hardware:

  1. Arduino or an arduino clone board (freeduino), or make your own custom arduino board with this tutorial.
  2. Hall effect sensor 44E or  US5881 or US1881.
  3. A small magnet.
  4. 10K resistor.
  5. 9V Battery and connector.
  6. Connecting wires and breadboard.

Software:

Arduino IDE

How does it work?

The Hall Effect sensor works on the principle of Hall Effect. According to which, whenever a magnetic field is applied in a direction perpendicular to the flow of electric current in a conductor, a potential difference is induced. This voltage can thus be used to detect whether the sensor is in the proximity of a magnet or not. The arduino can detect this voltage change through its interrupt pin and determine whether the magnet is near the sensor or not. The basic working of the Arduino hall effect sensor can be described as shown:

Arduino Hall sensor DIY Hacking

Arduino Hall Effect sensor working

There are many types of Hall Effect sensors, and depending on your project you should choose the right one. For applications in which speed of detection is not crucial, ordinary hall effect sensors like 44E can be used. However, for applications that involves high speed detection, like in the case of speedometers, high frequency hall effect sensors like US5881 or US1881 should be used. Mainly there are two types of hall effect sensors:

  1. Latching hall effect sensors.
  2. Non-latching hall effect sensors.

US1881 is a latching hall effect sensor. Here, the sensor gives out an output HIGH (5V) voltage whenever the north pole of a magnet is brought close to it. However, even when the magnet is removed the sensor still outputs a HIGH voltage and does not go LOW (0V) until the south pole of the magnet is brought close to it. These type of sensors that latches on to a particular state are called latched hall effect sensors.

US5881 is a non-latching hall effect sensor. Here, the sensor gives an output HIGH voltage whenever the north pole of a magnet is brought close to it. And, switches LOW whenever the magnet is removed. I personally prefer non-latching hall effect sensors like US5881 for my projects.

Hall effect sensors have three pins: VCC(5V), GND and Vout(Signal). The pin out of a hall effect sensor is as shown below:

Arduino Hall sensor pin out DIY Hacking

Arduino Hall Effect sensor pin out

Step 1: Connections for the Arduino Hall Effect Sensor

Interfacing the hall effect sensor with Arduino is really simple. The VCC of the sensor is connected to Arduino’s 5V power pin. The GND of the sensor is connected to the GND pin of Arduino. And the Vout or Signal pin of the hall effect sensor is connected to Arduino’s interrupt pin (digital pin 2). Furthermore, a 10K resistor is connected between the VCC and Vout pins of the hall effect sensor. This is done to pull the output of the hall effect sensor to 5V. The connections are done as shown below (the side having the printed number is facing towards you in the diagram):

Step 2:  Uploading the code and testing the Arduino Hall Effect sensor

After you finish hooking up the hall effect sensor to arduino, you need to upload the code to the board and test it. The code which can be used to detect a magnet and count the number of times it detects it can be found here: Arduino Hall Effect Sensor code. This is a very simple arduino code which utilizes the interrupt pin 0 (digital pin 2) of the arduino.

Whenever the hall effect sensor detects a magnet, it outputs a HIGH (5V) voltage to its Vout pin. The interrupt pin of the arduino which is connected to Vout, thus detects this rising (HIGH) voltage through the function: magnet_detect. A screenshot of the serial monitor which prints “detect” whenever a magnet is brought close to the sensor.

Arduino Hall Effect Sensor Tutorial DIY Hacking

Arduino Hall Effect Sensor serial monitor

Step 3: Hooking up the Arduino hall effect sensor to your project

Here, in order to show the applications of this project, I have installed the sensor on my door frame.  I have also attached a small magnet on to my door. Thus, whenever my door closes, I can detect it. This can also be used as a burglar alarm system by hooking it up to some lights/sirens.

Furthermore, you can also use this sensor to make a speedometer for your bike. Here, a small magnet needs to be attached to your wheel and the hall effect sensor could be attached to the frame of your bike. The number of rotations made by the wheel and the time taken for doing it can be measured through the hall effect sensor. And after performing some calculations on this data, you can show the speed of your bike in Km/h or Mp/H.

Check out this video which shows the demo for the Arduino hall effect sensor project:

 

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Showing 31 comments
  • Sergei BallsFallOff
    Reply

    Someone send me a shlong pic

  • Gurj
    Reply

    hi i looking i am new to this, but i use the code but serial monitor is printing letters with accent, can help with that? And also i looking for make sensor to detect car over the sensor can you recommend anything?

  • Anand Abraham
    Reply

    Hello Arvind,

    I am using the interrupt function as described on reading the hall effect pulse change across my motor. But my pulses read 0. No update.

    My arduino is running at 12V. My interrupt pin gets 8.5V at high & 5.64V at low.

    My interrupt ISR function is as follows:

    void count()
    {
    pulses++;
    }

    void setup()
    {
    // initialize serial communication:
    Serial.begin(9600);
    pinMode(2,INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(2),count,RISING);
    interrupts();
    }

    Do you know what the fault may be?

  • James ng
    Reply

    We wish to know more about these to increase speed to our bldc motor thru personal channel. Please contact me

  • farhan
    Reply

    Hi i wanted to ask is it possible to connect the output pin of the sensor to an analog pin on the arduino to see the different voltage values we would get for different magnets. thank you

  • Morai Motion
    Reply

    Great idea to use the Hall sensor for a home security system. Should be fairly easy to implement anywhere someone needs that extra level of protection with your clear instructions. Bike speedometer’s a good idea too, especially with the rise in popularity of cycle stationary-stands. Obviously there are many handy uses for it. Being in the linear motion industry, we find many people also like to use Hall sensors to control the motor timing of our micro linear actuators – being that they are electronic, there are always some minor timing delays when using multiple ones together – syncing them with a Hall sensor is an effective solution.

  • IAN
    Reply

    Gud day!
    Im student here in philippines looking for what sensor should be used to detect vehicle, although all can detect vehicle. Our thesis is “vehicle notifier in sharp curve road”

  • shazz
    Reply

    hi i want to ask can i find faults in wire using non latching Hall sensor ?
    i need a quick response please its urgent thanks

  • Doniel
    Reply

    Hello am a student trying to implement a similar project, i would like to know how to display the obtained rpm in an LCD. PLease advice, i keep trying but it fails

  • Joe Weisman
    Reply

    A couple of minor tips:
    – I use hall effect sensors with just the arduino’s internal pullup resistor, and I don’t add the 10K ohm or any other resistor. Works fine so far.
    – I’ve also wired a sensor using just 3 sequential arduino pins, which might be convenient in some cases:
    – pinMode(10, OUTPUT); digitalWrite(10, HIGH); // vcc
    – pinMode(11, OUTPUT); digitalWrite(11, LOW); // ground
    – pinMode(12, INPUT_PULLUP); // signal, low when magnet is sensed

  • Tim Yinger
    Reply

    Hi I’m new to all this. i just got the US5881 UA sensor, and on the data sheet it says “For proper operation, a 100nF bypass capacitor should be placed as close as possible to the device between the VDD and ground pin.” and the schematic shows both a 100nF capacitor and a 4.7 nF capacitor in the “typical 3-wire circuit”. However, there is also a schematic for a 2-wire circuit which does not use capacitors. Can you explain why you did not use capacitors in your setup? I’m counting revolutions of a small wheel (3-5″) and logging that data for analysis.
    Thank you

  • Oki E. Rinaldi
    Reply

    How long is the maximum distance that can be detected by the sensor?
    I need 5 to 10 cm distance between the sensor and the magnet. Can the sensor handle it? Or, do I need A ‘bigger’ magnet?

  • Don
    Reply

    I’m confused – don;t Hall Effect Sensors go low on output, not high? That pull-up resistor would make it high as of default, would it not?

  • Nik Fenning
    Reply

    Hi I am new to arduino in my head I can picture what I want the code to do but dont know how to do it, I am sure its a tiny adjustment to the code but how would I get it toprint just the rpm when there is an increase ?

    Thanks in Advance

    Blulander

  • Gaurav
    Reply

    rpm = 30*1000/(millis() – timeold)*half_revolutions;

    not getting the above statement whats the use of 30 and 1000 in above statement
    n suggest the modification to convert the code for bike speedometer in KM/Hr

  • Muhammed
    Reply

    oh, I am sorry.
    You hav already put a link but I did not see.

  • Muhammed
    Reply

    I am trying to do almost same thing to do university project.
    However, I am not good to use arduino codes.
    If you have this code, can you send me?

    best

  • santosh
    Reply

    Please List some non Latching Hall effect Sensors

    • Arvind Sanjeev
      Reply

      As said in the tutorial, US5881 is an optimal non latching hall effect sensor.

  • Daksh Gulati
    Reply

    Hi there!
    I wanted to ask if a Reed Switch will be better or a Hall Effect sensor will be better for measuring speed?
    I want to use it in an ATV.

    Thank you =)

    • Arvind Sanjeev
      Reply

      Personally, I have tried both. And I think the hall effect sensor: US5881 will suit your purpose best.

  • NaEun
    Reply

    Hi this is NaEun again!
    Thank you for your comment.
    It really helped us a lot :)

    But we have another problem about measuring the speed.
    When we stop the bike(spd==0) the speed value comes out the former speed, not changing to 0. We used “attachinterrupt” that you wrote.
    I’m wondering if you could solve this problem.

    I’ll be looking forward to get your comments.
    Thank you.

    • Arvind Sanjeev
      Reply

      You can perhaps create a code that checks if it takes a lot of time for the sensor to detect the next interrupt. That is, (if time_for_next_interrupt > long) then speed = 0, or something like that.

  • NaEun
    Reply

    Hello, I’m a student from Korea and I’m studying arduino.
    I’m making a speedometer and I cannot understand about the “half_revolution” in the code you uploaded. I’m curious what’s the use of it and why use the value 20 for the ‘if’ condition.

    I’ll be glad if you can response to my question:)
    Thanks!

    • Arvind Sanjeev
      Reply

      The half_revolution basically stores the count for the total number of revolutions. It is used to calculate the rpm (total revolutions/time), and 20 is just used as a starting threshold. For calibration, etc, only after the first 20 revolutions will we get the value for rpm.

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