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BH1750 digital light sensor library for Arduino

This is a 16-bit BH1750 digital ambient light sensor on a GY-302 breakout PCB:

Arduino library features

• Measurement in LUX
• Three operation modes:
  • Continues conversion
  • One-time conversion
• Three selectable resolutions:
  • Low 4 LUX resolution (low power)
  • High 1 LUX resolution
  • High 0.5 LUX resolution
• Asynchronous and synchronous conversion

BH1750 sensor specifications

• Operating voltage: 3.3V .. 4.5V max
• Low current by power down: max 1uA
• I2C bus interface: max 400kHz
• Ambience light:
  • Range: 1 - 65535 lx
  • Deviation: +/- 20%
  • Selectable resolutions:
    • 4 lx (low resolution, max 24 ms measurement time)
    • 1 lx (mid resolution max 180 ms measurement time)
    • 0.5 lx (high resolution 180 ms measurement time)
• No additional electronic components needed

GY-302 breakout specifications

• Supply voltage: 3.3 .. 5V
• 5V tolerant I2C SCL and SDA pins
• 2 selectable I2C addresses with ADDR pin high or low/floating

Hardware

Connection Arduino UNO board - BH1750

Note: Tested ESP8266 / ESP32 boards:

• ESP8266 boards: ESP12E / WeMos D1 & R2 / Node MCU v2 / v3
• ESP32 boards: WeMos LOLIN32 / LOLIN D32

Other unlisted MCU's may work, but are not tested.

WeMos LOLIN32 with OLED display

Change the following Wire initialization to:

// WeMos LOLIN32 with OLED support
Wire.begin(5, 4);

I2C address

• ADDR pin LOW for I2C address 0x23 (0x46 including R/W bit)

• ADDR pin HIGH for I2C address 0x5C (0xB8 including R/W bit)

Note: ADDR pin may be floating (open) which is the same as LOW.

Examples

Examples | Erriez BH1750:

• ContinuesMode | BH1750ContinuesAsynchronous
• ContinuesMode | BH1750ContinuesBasic
• ContinuesMode | BH1750ContinuesHighResolution
• ContinuesMode | BH1750ContinuesLowResolution
• ContinuesMode | BH1750ContinuesPowerMgt
• OneTimeMode | BH1750OneTimeBasic
• OneTimeMode| BH1750OneTimeHighResolution
• OneTimeMode| BH1750OneTimeLowResolution
• OneTimeMode| BH1750OneTimePowerMgt

Documentation

• Doxygen online HTML
• Doxygen PDF
• BH1750 chip datasheet

Example continues conversion high resolution

#include <Wire.h>
#include <ErriezBH1750.h>

// ADDR line LOW/open:  I2C address 0x23 (0x46 including R/W bit) [default]
// ADDR line HIGH:      I2C address 0x5C (0xB8 including R/W bit)
BH1750 sensor(LOW);

void setup()
{
  Serial.begin(115200);
  Serial.println(F("BH1750 continues measurement high resolution example"));

  // Initialize I2C bus
  Wire.begin();

  // Initialize sensor in continues mode, high 0.5 lx resolution
  sensor.begin(ModeContinuous, ResolutionHigh);

  // Start conversion
  sensor.startConversion();
}

void loop()
{
  uint16_t lux;

  // Wait for completion (blocking busy-wait delay)
  if (sensor.isConversionCompleted()) {
    // Read light
    lux = sensor.read();

    // Print light
    Serial.print(F("Light: "));
    Serial.print(lux / 2);
    Serial.print(F("."));
    Serial.print(lux % 10);
    Serial.println(F(" LUX"));
  }
}

Output

BH1750 continues measurement high resolution example
Light: 15.0 LUX
Light: 31.2 LUX
Light: 385.0 LUX
Light: 575.1 LUX
Light: 667.5 LUX

Usage

Initialization

#include <Wire.h>
#include <ErriezBH1750.h>

// ADDR line LOW/open:  I2C address 0x23 (0x46 including R/W bit) [default]
// ADDR line HIGH:      I2C address 0x5C (0xB8 including R/W bit)
BH1750 sensor(LOW);

void setup()
{
  	// Initialize I2C bus
  	Wire.begin();
    
    // Initialize sensor with a mode and resolution:
    //   Modes:
    //     ModeContinuous
    //     ModeOneTime
    //   Resolutions:
    //     ResolutionLow (4 lx resolution)
    //     ResolutionMid (1 lx resolution)
    //     ResolutionHigh (0.5 lx resolution)
    sensor.begin(mode, resolution);
}

Start conversion

Wire.begin(); and sensor.begin(); must be called before starting the conversion:

sensor.startConversion();

Wait for completion asynchronous (non-blocking)

The sensor conversion completion status can be checked asynchronously before reading the light value:

bool completed = sensor.isConversionCompleted();

Wait for completion synchronous (blocking)

The sensor conversion completion status can be checked synchronously before reading the light value:

// Wait for completion
// completed = false: Timeout or device in power-down
bool completed = sensor.waitForCompletion();

Read light value in LUX

One-time mode: The application must wait or check for a completed conversion, otherwise the sensor may return an invalid value. Continues mode: The application can call this function without checking completion, but is not recommended when accurate values are required.

Read sensor light value:

// lux = 0: No light or not initialized
uint16_t lux = sensor.read();

For 4 lx low and 1 lx high resolutions:

// Print low and medium resolutions
Serial.print(F("Light: "));
Serial.print(lux);
Serial.println(F(" LUX"));

For 0.5 lx high resolution:

// Print high resolution
Serial.print(F("Light: "));
Serial.print(lux / 2);
Serial.print(F("."));
Serial.print(lux % 10);
Serial.println(F(" LUX"));

Power down

The device enters power down automatically after a one-time conversion.

A manual power-down in continues mode can be generated by calling:

sensor.powerDown();

Library dependencies

• Built-in Wire.h

Library installation

Please refer to the Wiki page.

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