Meadow.Foundation.Sensors.LoadCell.Nau7802

Nau7802
Status
Source code	GitHub
Datasheet(s)	GitHub
NuGet package

Code Example

private Nau7802 loadSensor;

public int CalibrationFactor { get; set; } = 16526649; // TODO: change this based on your scale (using the method provided below)
public Mass CalibrationWeight { get; set; } = new Mass(1600, Mass.UnitType.Grams); // TODO: enter the known-weight you used in calibration

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

    loadSensor = new Nau7802(Device.CreateI2cBus());

    if (CalibrationFactor == 0)
    {
        await GetAndDisplayCalibrationUnits(loadSensor);
    }
    else
    {   // wait for the ADC to settle
        await Task.Delay(500);

        // Set the current load to be zero
        loadSensor.SetCalibrationFactor(CalibrationFactor, CalibrationWeight);
        loadSensor.Tare();
    }

    loadSensor.Updated += (sender, values) => Resolver.Log.Info($"Mass is now returned {values.New.Grams:N2}g");
}

public override Task Run()
{
    loadSensor.StartUpdating(TimeSpan.FromSeconds(2));

    return Task.CompletedTask;
}

public async Task GetAndDisplayCalibrationUnits(Nau7802 sensor)
{
    // first notify the user we're starting
    Resolver.Log.Info($"Beginning Calibration. First we'll tare (set a zero).");
    Resolver.Log.Info($"Make sure scale bed is clear. Next step in 5 seconds...");

    await Task.Delay(5000);
    sensor.Tare();
    Resolver.Log.Info($"Place a known weight on the scale. Next step in 5 seconds...");

    await Task.Delay(500);
    var factor = sensor.CalculateCalibrationFactor();

    Resolver.Log.Info($"Your scale's Calibration Factor is: {factor}. Enter this into the code for future use.");
}

Sample project(s) available on GitHub

Class Nau7802

24-Bit Dual-Channel ADC For Bridge Sensors

Assembly: Nau7802.dll

View Source

Declaration

public class Nau7802 : ByteCommsSensorBase<Mass>, IObservable<IChangeResult<Mass>>, IDisposable, IMassSensor, ISamplingSensor<Mass>, ISensor<Mass>, ISensor, ISamplingSensor, II2cPeripheral

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

Implements:
System.IObservable<Meadow.IChangeResult<Meadow.Units.Mass>>, System.IDisposable, Meadow.Peripherals.Sensors.Mass.IMassSensor, Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.Mass>, Meadow.Peripherals.Sensors.ISensor<Meadow.Units.Mass>, Meadow.Peripherals.Sensors.ISensor, Meadow.Peripherals.Sensors.ISamplingSensor, Meadow.Hardware.II2cPeripheral

Properties

DefaultSamplePeriod

Default sample period

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Declaration

public TimeSpan DefaultSamplePeriod { get; }

Mass

The last read Mass

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Declaration

public Mass? Mass { get; }

DefaultI2cAddress

The default I2C address for the peripheral

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Declaration

public byte DefaultI2cAddress { get; }

Methods

Tare()

Tares the sensor, effectively setting the current weight reading to relative zero.

View Source

Declaration

public void Tare()

CalculateCalibrationFactor()

Calculates the calibration factor of the load cell Call this method with a known weight on the sensor, and then use the returned value in a call before using the sensor

View Source

Declaration

public int CalculateCalibrationFactor()

Returns

System.Int32: The calibration factor as an int### SetCalibrationFactor(int, Mass) Sets the sensor's calibration factor based on a factor calculated with a know weight by calling Meadow.Foundation.Sensors.LoadCell.Nau7802.CalculateCalibrationFactor().

View Source

Declaration

public void SetCalibrationFactor(int factor, Mass knownValue)

Parameters

Type	Name
System.Int32	factor
Meadow.Units.Mass	knownValue

ReadSensor()

Reads data from the sensor

View Source

Declaration

protected override Task<Mass> ReadSensor()

Returns

System.Threading.Tasks.Task<Meadow.Units.Mass>: The latest sensor reading

Implements

• System.IObservable<Meadow.IChangeResult<Meadow.Units.Mass>>
• System.IDisposable
• Meadow.Peripherals.Sensors.Mass.IMassSensor
• Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.Mass>
• Meadow.Peripherals.Sensors.ISensor<Meadow.Units.Mass>
• Meadow.Peripherals.Sensors.ISensor
• Meadow.Peripherals.Sensors.ISamplingSensor
• Meadow.Hardware.II2cPeripheral