Remarks

Fc28
Status
Source code	GitHub
Datasheet(s)	GitHub
NuGet package

FC-28 Soil Moisture Sensor is a simple breakout for measuring the moisture in soil and similar materials. The sensor has two probes and measures the resistance between them, which means this sensor is of type Resistive. Since water is conductive, as moisture in the soil increases, the resistance decreases allowing the sensor to determine soil humidity.

The biggest issue of this sensor is the corrosion of the probes, not just because it is in contact with the soil but also because there is a DC current flowing which causes electrolysis of the sensors. A work-around to prolong the life of the probes is to not constantly have the sensor powered on, but activate it every time the sensor will perform a read using a digital output port connected to the VCC pin. The code and circuit example shows you how to use it.

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

public class MeadowApp : App<F7Micro, MeadowApp>
{
    Fc28 fc28;

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

        fc28 = new Fc28(
            Device.CreateAnalogInputPort(Device.Pins.A01),
            Device.CreateDigitalOutputPort(Device.Pins.D15),
            minimumVoltageCalibration: 3.24f,
            maximumVoltageCalibration: 2.25f
        );

        TestFC28Updating();
    }

    void TestFC28Updating() 
    {
        Console.WriteLine("TestFC28Updating...");

        fc28.Subscribe(new FilterableObserver<FloatChangeResult, float>(
            h => { Console.WriteLine($"Moisture values: {Math.Truncate(h.New)}, old: {Math.Truncate(h.Old)}, delta: {h.DeltaPercent}"); },
            e => { return true; }
        ));

        fc28.Updated += (object sender, FloatChangeResult e) =>
        {
            Console.WriteLine($"Moisture Updated: {e.New}");
        };

        fc28.StartUpdating();
    }
}

Sample projects available on GitHub

Code Example

Fc28 fc28;

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

    fc28 = new Fc28(
        Device.CreateAnalogInputPort(Device.Pins.A01, 5, TimeSpan.FromMilliseconds(40), new Voltage(3.3, Voltage.UnitType.Volts)),
        Device.CreateDigitalOutputPort(Device.Pins.D15),
        minimumVoltageCalibration: new Voltage(3.24f, VU.Volts),
        maximumVoltageCalibration: new Voltage(2.25f, VU.Volts)
    );

    var consumer = Fc28.CreateObserver(
        handler: result => {
            // the first time through, old will be null.
            string oldValue = (result.Old is { } old) ? $"{old:n2}" : "n/a"; // C# 8 pattern matching
            Resolver.Log.Info($"Subscribed - " +
                $"new: {result.New}, " +
                $"old: {oldValue}");
        },
        filter: null
    );
    fc28.Subscribe(consumer);

    fc28.HumidityUpdated += (object sender, IChangeResult<double> e) =>
    {
        Resolver.Log.Info($"Moisture Updated: {e.New}");
    };

    return Task.CompletedTask;
}

public async override Task Run()
{
    var moisture = await fc28.Read();
    Resolver.Log.Info($"Moisture Value { moisture}");

    fc28.StartUpdating(TimeSpan.FromMilliseconds(5000));
}

Sample project(s) available on GitHub

Wiring Example

Characteristic	Locus
Inheritance	System.Object ObservableBase<System.Double> SamplingSensorBase<System.Double> > Fc28
Implements	ISamplingSensor<System.Double> IMoistureSensor
Inherited Members	SamplingSensorBase<Double>.samplingLock SamplingSensorBase<Double>.Updated SamplingSensorBase<Double>.SamplingTokenSource SamplingSensorBase<Double>.Conditions SamplingSensorBase<Double>.IsSampling SamplingSensorBase<Double>.UpdateInterval SamplingSensorBase<Double>.RaiseEventsAndNotify(IChangeResult<>) SamplingSensorBase<Double>.Read() ObservableBase<Double>.observers ObservableBase<Double>.NotifyObservers(IChangeResult<>) Meadow.Foundation.ObservableBase<System.Double>.Subscribe(IObserver<>) Meadow.Foundation.ObservableBase<System.Double>.CreateObserver(Action<>, System.Nullable<Predicate<IChangeResult<UNIT>>>)
Namespace	Meadow.Foundation.Sensors.Moisture
Assembly	Fc28.dll

Syntax

public class Fc28 : SamplingSensorBase<double>, ISamplingSensor<double>, IMoistureSensor

Constructors

Fc28(IAnalogInputPort, IDigitalOutputPort, Nullable<Voltage>, Nullable<Voltage>)

Creates a FC28 soil moisture sensor object with the especified analog pin and digital pin

Declaration

public Fc28(IAnalogInputPort analogInputPort, IDigitalOutputPort digitalOutputPort, Voltage? minimumVoltageCalibration, Voltage? maximumVoltageCalibration)

Parameters

Type	Name	Description
IAnalogInputPort	analogInputPort	Analog input port connected
IDigitalOutputPort	digitalOutputPort	Digital output port connected
System.Nullable<Voltage>	minimumVoltageCalibration	Minimum Voltage Calibration value
System.Nullable<Voltage>	maximumVoltageCalibration	Maximum Voltage Calibration value

Fc28(IPin, IPin, Nullable<Voltage>, Nullable<Voltage>, Nullable<TimeSpan>, Int32, Nullable<TimeSpan>)

Creates a FC28 soil moisture sensor object with the especified analog pin, digital pin and IO device

Declaration

public Fc28(IPin analogInputPin, IPin digitalOutputPin, Voltage? minimumVoltageCalibration, Voltage? maximumVoltageCalibration, TimeSpan? updateInterval = null, int sampleCount = 5, TimeSpan? sampleInterval = null)

Parameters

Type	Name	Description
IPin	analogInputPin	Analog input pin connected
IPin	digitalOutputPin	Digital output pin connected
System.Nullable<Voltage>	minimumVoltageCalibration	Minimum Voltage Calibration value
System.Nullable<Voltage>	maximumVoltageCalibration	Maximum Voltage Calibration value
System.Nullable<TimeSpan>	updateInterval	The time, to wait between sets of sample readings. This value determines how oftenChanged events are raised and IObservable consumers are notified.
System.Int32	sampleCount	How many samples to take during a given reading. These are automatically averaged to reduce noise.
System.Nullable<TimeSpan>	sampleInterval	The time, to wait in between samples during a reading.

Properties

AnalogInputPort

Returns the analog input port

Declaration

protected IAnalogInputPort AnalogInputPort { get; }

Property Value

Type	Description
IAnalogInputPort

DigitalOutputPort

Returns the digital output port

Declaration

protected IDigitalOutputPort DigitalOutputPort { get; }

Property Value

Type	Description
IDigitalOutputPort

MaximumVoltageCalibration

Voltage value of most moist soil. Default of 3.3V

Declaration

public Voltage MaximumVoltageCalibration { get; set; }

Property Value

Type	Description
Voltage

MinimumVoltageCalibration

Voltage value of most dry soil. Default of 0V

Declaration

public Voltage MinimumVoltageCalibration { get; set; }

Property Value

Type	Description
Voltage

Moisture

Last value read from the moisture sensor

Declaration

public double? Moisture { get; }

Property Value

Type	Description
System.Nullable<System.Double>

Methods

RaiseChangedAndNotify(IChangeResult<Double>)

Raise change events for subscribers

Declaration

protected void RaiseChangedAndNotify(IChangeResult<double> changeResult)

Parameters

Type	Name	Description
IChangeResult<System.Double>	changeResult	The change result with the current sensor data

ReadSensor()

Reads data from the sensor

Declaration

protected override Task<double> ReadSensor()

Returns

Type	Description
Task<System.Double>	The latest sensor reading

Overrides

Meadow.Foundation.SamplingSensorBase<System.Double>.ReadSensor()

StartUpdating(Nullable<TimeSpan>)

Starts continuously sampling the sensor

Declaration

public override void StartUpdating(TimeSpan? updateInterval)

Parameters

Type	Name	Description
System.Nullable<TimeSpan>	updateInterval

StopUpdating()

Stops sampling the sensor

Declaration

public override void StopUpdating()

Overrides

Meadow.Foundation.SamplingSensorBase<System.Double>.StopUpdating()

VoltageToMoisture(Voltage)

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

Declaration

protected double VoltageToMoisture(Voltage voltage)

Parameters

Type	Name	Description
Voltage	voltage

Returns

Type	Description
System.Double

Events

HumidityUpdated

Raised when a new sensor reading has been made. To enable, call StartUpdating().

Declaration

public event EventHandler<IChangeResult<double>> HumidityUpdated

Event Type

Type	Description
EventHandler<IChangeResult<System.Double>>