Remarks

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

Wiring Example

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

Syntax

public class Capacitive : FilterableChangeObservableBase<FloatChangeResult, float>, IMoistureSensor

Constructors

Capacitive(IAnalogInputPort, Single, Single)

Creates a Capacitive soil moisture sensor object with the especified AnalogInputPort.

Declaration

public Capacitive(IAnalogInputPort analogPort, float minimumVoltageCalibration = 0F, float maximumVoltageCalibration = 3.3F)

Parameters

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

Capacitive(IIODevice, IPin, Single, Single)

Creates a Capacitive soil moisture sensor object with the specified analog pin and a IO device.

Declaration

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

Parameters

Type	Name	Description
IIODevice	device
IPin	analogPin
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

IsSampling

Gets a value indicating whether the analog input port is currently sampling the ADC. 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; protected set; }

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>