Meadow.Foundation.Sensors.HallEffect.LinearHallEffectTachometer

LinearHallEffectTachometer
Status	Not Tested
Source code	GitHub
NuGet package

A Hall effect sensor is a device that is used to measure the magnitude of a magnetic field. Its output voltage is directly proportional to the magnetic field strength through it. These sensors are commonly used for proximity sensing, positioning, speed detection, and current sensing applications.

Frequently, a Hall sensor is combined with threshold detection so that it acts as and is called a switch. Commonly seen in industrial applications such as the pictured pneumatic cylinder, they are also used in consumer equipment; for example some computer printers use them to detect missing paper and open covers. They can also be used in computer keyboards, an application that requires ultra-high reliability.

Hall sensors are commonly used to time the speed of wheels and shafts, such as for internal combustion engine ignition timing, tachometers and anti-lock braking systems. They are used in brushless DC electric motors to detect the position of the permanent magnet. In the pictured wheel with two equally spaced magnets, the voltage from the sensor will peak twice for each revolution. This arrangement is commonly used to regulate the speed of disk drives.

The following example instantiates a LinearHallEffectTachometer object, and registers the RPMsChanged event handler, and it outputs the RPMs in the output console. To trigger the event of the sensor, you can place a magnet on a rotating object like a small motor, or even a fidget spinner, and make sure that the magnet passes very close to the sensor in every rotation so it picks up the electromagnetic field and it will start measuring RPMs.

Code Example

The following example prints horizontal and vertical values ranging from -1 to 1, 0 being the center position:

public class MeadowApp : App<F7Micro, MeadowApp>
{
    public MeadowApp()
    {
        LinearHallEffectTachometer hallSensor;

        public MeadowApp()
        {
            Console.Write("Initializing...");

            hallSensor = new LinearHallEffectTachometer(
                inputPort: Device.CreateDigitalInputPort(Device.Pins.D02, Meadow.Hardware.InterruptMode.EdgeRising, Meadow.Hardware.ResistorMode.InternalPullUp, 0, 10),
                type: CircuitTerminationType.CommonGround,
                numberOfMagnets: 2,
                rpmChangeNotificationThreshold: 1);
            hallSensor.RPMsChanged += HallSensorRPMsChanged;

            Console.WriteLine("done");
        }

        void HallSensorRPMsChanged(object sender, ChangeResult<float> e)
        {
            Console.WriteLine($"RPM: {e.New}");
        }
    }
}

Sample projects available on GitHub

Wiring Example

Class LinearHallEffectTachometer

Represents a Lineal Hall Effect tachometer.

Assembly: Meadow.Foundation.dll

View Source

Declaration

public class LinearHallEffectTachometer : IDisposable

Implements:
System.IDisposable

Properties

RPMChangeNotificationThreshold

Any changes to the RPMs that are greater than the RPM change threshold will cause an event to be raised when the instance is set to update automatically.

View Source

Declaration

public float RPMChangeNotificationThreshold { get; set; }

InputPort

Input port for the tachometer

View Source

Declaration

protected IDigitalInterruptPort InputPort { get; set; }

NumberOfMagnets

Returns number of magnets of the sensor.

View Source

Declaration

public ushort NumberOfMagnets { get; }

RPMs

Returns number of revolutions per minute.

View Source

Declaration

public int RPMs { get; }

IsDisposed

Is the object disposed

View Source

Declaration

public bool IsDisposed { get; }

Fields

rpms

Revolutions per minute

View Source

Declaration

protected float rpms

lastNotifiedRPMs

Last notified RPM value

View Source

Declaration

protected float lastNotifiedRPMs

revolutionTimeStart

Revolution start time

View Source

Declaration

protected DateTime revolutionTimeStart

numberOfReads

Number of reads

View Source

Declaration

protected ushort numberOfReads

Methods

OnRaiseRPMChanged()

Notify when RPMs change

View Source

Declaration

protected void OnRaiseRPMChanged()

Dispose()

Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.

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Declaration

public void Dispose()

Dispose(bool)

Dispose of the object

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Declaration

protected virtual void Dispose(bool disposing)

Parameters

Type	Name	Description
System.Boolean	disposing	Is disposing

Events

RPMsChanged

Event raised when the RPM change is greater than the RPMChangeNotificationThreshold value.

View Source

Declaration

public event EventHandler<ChangeResult<float>> RPMsChanged

Event Type

System.EventHandler<Meadow.ChangeResult<System.Single>>

Implements

• System.IDisposable