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

Pins board - BH1750	VCC	GND	SDA	SCL
Arduino UNO (ATMega328 boards)	5V	GND	A4	A5
Arduino Mega2560	5V	GND	D20	D21
Arduino Leonardo	5V	GND	D2	D3
Arduino DUE (ATSAM3X8E)	3V3	GND	20	21
ESP8266	3V3	GND	GPIO4 (D2)	GPIO5 (D1)
ESP32	3V3	GND	GPIO21	GPIO22

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.

Other Arduino Libraries and Sketches from Erriez

• Erriez Libraries and Sketches