Characteristic	Locus
Inheritance	System.Object > FC28
Implements	IMoistureSensor
Namespace	Meadow.Foundation.Sensors.Moisture
Assembly	FC28.dll

Syntax

public class FC28 : FilterableObservableBase<FloatChangeResult, float>, IMoistureSensor

Remarks

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 workararound to prolong the life of the probes is to not constantly have the sensor powered on, but activate it everytime 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.

Examples

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

using System.Threading;
using Meadow;
using Meadow.Foundation.Sensors.Moisture;

namespace FC28_Sample
{
    public class Program
    {
        static IApp _app; 
        public static void Main()
        {
            _app = new App();
        }
    }

    public class App : AppBase<F7Micro, App>
    {
        FC28 _FC28;

        public App ()
        {
            // create a new FC-28 object connected to analog pin A01 and digital pin 14
            _FC28 = new FC28(Device.Pins.A01, Device.Pins.D14);

            Run();
        }

        async Task Run()
        {
            while (true)
            {
                float moisture = await _FC28.Read();
                Console.WriteLine($"Moisture: {0}", moisture);
                Thread.Sleep(1000);
            }
        }
    }
}

Example Circuit

Constructors

FC28(IAnalogInputPort, IDigitalOutputPort, Single, Single)

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

Declaration

public FC28(IAnalogInputPort analogPort, IDigitalOutputPort digitalPort, float minimumVoltageCalibration = 0F, float maximumVoltageCalibration = 3.3F)

Parameters

Type	Name	Description
IAnalogInputPort	analogPort
IDigitalOutputPort	digitalPort
System.Single	minimumVoltageCalibration
System.Single	maximumVoltageCalibration

FC28(IIODevice, IPin, IPin, Single, Single)

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

Declaration

public FC28(IIODevice device, IPin analogPin, IPin digitalPin, float minimumVoltageCalibration = 0F, float maximumVoltageCalibration = 3.3F)

Parameters

Type	Name	Description
IIODevice	device
IPin	analogPin
IPin	digitalPin
System.Single	minimumVoltageCalibration
System.Single	maximumVoltageCalibration

Properties

AnalogInputPort

Returns the analog input port

Declaration

public IAnalogInputPort AnalogInputPort { get; protected set; }

Property Value

Type	Description
IAnalogInputPort

DigitalPort

Returns the digital output port

Declaration

public IDigitalOutputPort DigitalPort { get; protected set; }

Property Value

Type	Description
IDigitalOutputPort

IsSampling

Gets a value indicating whether the sensor is currently in a sampling loop. Call StartSampling() to spin up the sampling process.

Declaration

public bool IsSampling { get; protected set; }

Property Value

Type	Description
System.Boolean	true if sampling; otherwise, false.

MaximumVoltageCalibration

Voltage value of most moist soil

Declaration

public float MaximumVoltageCalibration { get; set; }

Property Value

Type	Description
System.Single

MinimumVoltageCalibration

Voltage value of most dry soil

Declaration

public float MinimumVoltageCalibration { get; set; }

Property Value

Type	Description
System.Single

Moisture

Last value read from the moisture sensor.

Declaration

public float Moisture { get; }

Property Value

Type	Description
System.Single

Methods

Map(Single, Single, Single, Single, Single)

Re-maps a value from one range (fromLow - fromHigh) to another (toLow - toHigh).

Declaration

protected float Map(float value, float fromLow, float fromHigh, float toLow, float toHigh)

Parameters

Type	Name	Description
System.Single	value
System.Single	fromLow
System.Single	fromHigh
System.Single	toLow
System.Single	toHigh

Returns

Type	Description
System.Single

RaiseChangedAndNotify(FloatChangeResult)

Declaration

protected void RaiseChangedAndNotify(FloatChangeResult changeResult)

Parameters

Type	Name	Description
FloatChangeResult	changeResult

Read(Int32, Int32)

Convenience method to get the current soil moisture. For frequent reads, use StartUpdating() and StopUpdating().

Declaration

public Task<float> Read(int sampleCount = 10, int sampleInterval = 40)

Parameters

Type	Name	Description
System.Int32	sampleCount	The number of sample readings to take. Must be greater than 0.
System.Int32	sampleInterval	The interval, in milliseconds, between sample readings.

Returns

Type	Description
System.Threading.Tasks.Task<System.Single>

StartUpdating(Int32, Int32, Int32)

Starts continuously sampling the sensor.

This method also starts raising Updated events and IObservable subscribers getting notified. Use the standbyDuration parameter to specify how often events and notifications are raised/sent.

Declaration

public void StartUpdating(int sampleCount = 10, int sampleIntervalDuration = 40, int standbyDuration = 1000)

Parameters

Type	Name	Description
System.Int32	sampleCount	How many samples to take during a given reading. These are automatically averaged to reduce noise.
System.Int32	sampleIntervalDuration	The time, in milliseconds, to wait in between samples during a reading.
System.Int32	standbyDuration	The time, in milliseconds, to wait between sets of sample readings. This value determines how often Updated events are raised and IObservable consumers are notified.

StopUpdating()

Stops sampling the sensor.

Declaration

public void StopUpdating()

VoltageToMoisture(Single)

Declaration

protected float VoltageToMoisture(float voltage)

Parameters

Type	Name	Description
System.Single	voltage

Returns

Type	Description
System.Single

Events

Updated

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

Declaration

public event EventHandler<FloatChangeResult> Updated

Event Type

Type	Description
System.EventHandler<FloatChangeResult>