Meadow.Foundation.Sensors.Light.Bh1750

Bh1750
Status
Source code	GitHub
Datasheet(s)	GitHub
NuGet package

The BH1750 is a light intensity sensor that communicates over I2C.

Code Example

Bh1750 sensor;

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

    var i2c = Device.CreateI2cBus();
    sensor = new Bh1750(
        i2c,
        measuringMode: Mode.ContinuouslyHighResolutionMode, // the various modes take differing amounts of time.
        lightTransmittance: 1 // lower this to increase sensitivity, for instance, if it's behind a semi opaque window
        );

    // Example that uses an IObservable subscription to only be notified when the filter is satisfied
    var consumer = Bh1750.CreateObserver(
        handler: result => Resolver.Log.Info($"Observer: filter satisfied: {result.New.Lux:N2}Lux, old: {result.Old?.Lux:N2}Lux"),

        // only notify if the visible light changes by 100 lux (put your hand over the sensor to trigger)
        filter: result =>
        {
            if (result.Old is { } old)
            {
                // returns true if > 100lux change
                return ((result.New - old).Abs().Lux > 100);
            }
            return false;
        });
    sensor.Subscribe(consumer);

    // classical .NET events can also be used:
    sensor.Updated += (sender, result) => Resolver.Log.Info($"Light: {result.New.Lux:N2}Lux");

    return Task.CompletedTask;
}

public override async Task Run()
{
    var result = await sensor.Read();
    Resolver.Log.Info("Initial Readings:");
    Resolver.Log.Info($" Light: {result.Lux:N2}Lux");

    sensor.StartUpdating(TimeSpan.FromSeconds(1));
}

Sample project(s) available on GitHub

Wiring Example

To wire a Bh1750 to your Meadow board, connect the following:

Bh1750	Meadow Pin
GND	GND
SCL	D08 (SCL)
SDA	D07 (SDA)
VCC	3V3

It should look like the following diagram:

Class Bh1750

Represents a BH1750 ambient light sensor

Assembly: Bh1750.dll

View Source

Declaration

public class Bh1750 : ByteCommsSensorBase<Illuminance>, IObservable<IChangeResult<Illuminance>>, IDisposable, ILightSensor, ISamplingSensor<Illuminance>, ISensor<Illuminance>, ISensor, ISamplingSensor, II2cPeripheral

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

Implements:
System.IObservable<Meadow.IChangeResult<Meadow.Units.Illuminance>>, System.IDisposable, Meadow.Peripherals.Sensors.Light.ILightSensor, Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.Illuminance>, Meadow.Peripherals.Sensors.ISensor<Meadow.Units.Illuminance>, Meadow.Peripherals.Sensors.ISensor, Meadow.Peripherals.Sensors.ISamplingSensor, Meadow.Hardware.II2cPeripheral

Properties

LightTransmittance

BH1750 Light Transmittance (27.20-222.50%)

View Source

Declaration

public double LightTransmittance { get; set; }

MeasuringMode

BH1750 Measuring Mode

View Source

Declaration

public Bh1750.MeasuringModes MeasuringMode { get; set; }

Illuminance

The current illuminance read by the sensor

View Source

Declaration

public Illuminance? Illuminance { get; }

DefaultI2cAddress

The default I2C address for the peripheral

View Source

Declaration

public byte DefaultI2cAddress { get; }

Methods

ReadSensor()

Read the current luminosity

View Source

Declaration

protected override Task<Illuminance> ReadSensor()

Returns

System.Threading.Tasks.Task<Meadow.Units.Illuminance>: The current Illuminance value

Implements

• System.IObservable<Meadow.IChangeResult<Meadow.Units.Illuminance>>
• System.IDisposable
• Meadow.Peripherals.Sensors.Light.ILightSensor
• Meadow.Peripherals.Sensors.ISamplingSensor<Meadow.Units.Illuminance>
• Meadow.Peripherals.Sensors.ISensor<Meadow.Units.Illuminance>
• Meadow.Peripherals.Sensors.ISensor
• Meadow.Peripherals.Sensors.ISamplingSensor
• Meadow.Hardware.II2cPeripheral