Meadow.Foundation.Sensors.Moisture.Capacitive

Capacitive
Status
Source code	GitHub
NuGet package

Capacitive Soil Moisture sensor is a simple breakout for measuring the moisture in soil and similar materials. This sensor measures moisture levels by capacitive sensing, rather then resistive sensing like other types of moisture sensor such as the FC-28.

Capacitive sensing means measuring the dielectrum that is formed by the soil and the water is the most important factor that forms the dielectrum. Even though this kind of sensor might be a little pricier, it is made of corrosion resistant material giving it a longer service of life than a resistive sensor.

The following example shows how read the soil moisture every second:

public class MeadowApp : App<F7Micro, MeadowApp>
{
    Capacitive _Capacitive;

    public MeadowApp()
    {
        // create a new Capacitive sensor object connected to analog pin A01
        _Capacitive = new Capacitive(Device.Pins.A01);

        Run();
    }

    async Task Run()
    {
        while (true)
        {
            float moisture = await _Capacitive.Read();
            Console.WriteLine($"Moisture: {0}", moisture);
            Thread.Sleep(1000);
        }
    }
}

Sample projects available on GitHub

Code Example

Capacitive capacitive;

public override Task Initialize()
{
    Resolver.Log.Info("Initialize...");

    capacitive = new Capacitive(
        Device.Pins.A00,
        minimumVoltageCalibration: new Voltage(2.84f),
        maximumVoltageCalibration: new Voltage(1.63f)
    );

    // Example that uses an IObservable subscription to only be notified when the moisture changes by filter defined.
    var consumer = Capacitive.CreateObserver(
        handler: result =>
        {
            string oldValue = (result.Old is { } old) ? $"{old:n2}" : "n/a";
            Resolver.Log.Info($"Subscribed - " +
                $"new: {result.New}, " +
                $"old: {oldValue}");
        },
        filter: null
    );
    capacitive.Subscribe(consumer);

    // classical .NET events can also be used:
    capacitive.Updated += (sender, result) =>
    {
        string oldValue = (result.Old is { } old) ? $"{old:n2}" : "n/a";
        Resolver.Log.Info($"Updated - New: {result.New}, Old: {oldValue}");
    };

    //==== One-off reading use case/pattern
    ReadSensor().Wait();

    capacitive.StartUpdating(TimeSpan.FromMilliseconds(1000));

    return Task.CompletedTask;
}

protected async Task ReadSensor()
{
    var moisture = await capacitive.Read();
    Resolver.Log.Info($"Initial moisture: {moisture:n2}");
}

Sample project(s) available on GitHub

Wiring Example

Class Capacitive

Capacitive Soil Moisture Sensor

Assembly: Capacitive.dll

View Source

Declaration

public class Capacitive : SamplingSensorBase<double>, IObservable<IChangeResult<double>>, IMoistureSensor, ISamplingSensor<double>, ISensor<double>, ISensor, ISamplingSensor, IDisposable

Inheritance: System.Object -> Meadow.Foundation.ObservableBase<UNIT>

Implements:
System.IObservable<Meadow.IChangeResult<System.Double>>, Meadow.Peripherals.Sensors.Moisture.IMoistureSensor, Meadow.Peripherals.Sensors.ISamplingSensor<System.Double>, Meadow.Peripherals.Sensors.ISensor<System.Double>, Meadow.Peripherals.Sensors.ISensor, Meadow.Peripherals.Sensors.ISamplingSensor, System.IDisposable

Properties

AnalogInputPort

Returns the analog input port

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Declaration

protected IAnalogInputPort AnalogInputPort { get; }

Moisture

Last value read from the moisture sensor

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Declaration

public double? Moisture { get; protected set; }

MinimumVoltageCalibration

Voltage value of most dry soil - default is 0 volts

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Declaration

public Voltage MinimumVoltageCalibration { get; set; }

MaximumVoltageCalibration

Voltage value of most moist soil - default of 3.3V

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Declaration

public Voltage MaximumVoltageCalibration { get; set; }

IsDisposed

Is the object disposed

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Declaration

public bool IsDisposed { get; }

Methods

ReadSensor()

Reads data from the sensor

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Declaration

protected override Task<double> ReadSensor()

Returns

System.Threading.Tasks.Task<System.Double>: The latest sensor reading### StartUpdating(TimeSpan?) Starts continuously sampling the sensor

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Declaration

public override void StartUpdating(TimeSpan? updateInterval)

Parameters

Type	Name
System.Nullable<System.TimeSpan>	updateInterval

StopUpdating()

Stops sampling the sensor

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Declaration

public override void StopUpdating()

VoltageToMoisture(Voltage)

Converts voltage to moisture value, ranging from 0 (most dry) to 1 (most wet)

View Source

Declaration

protected double VoltageToMoisture(Voltage voltage)

Returns

System.Double

Parameters

Type	Name
Meadow.Units.Voltage	voltage

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

Implements

• System.IObservable<Meadow.IChangeResult<System.Double>>
• Meadow.Peripherals.Sensors.Moisture.IMoistureSensor
• Meadow.Peripherals.Sensors.ISamplingSensor<System.Double>
• Meadow.Peripherals.Sensors.ISensor<System.Double>
• Meadow.Peripherals.Sensors.ISensor
• Meadow.Peripherals.Sensors.ISamplingSensor
• System.IDisposable