Introduction
The BH1750 is a digital ambient light sensor that measures light intensity using a photodiode. The photodiode contains a PN junction, which generates electron–hole pairs in the depletion region when light falls on it.
Due to the internal photoelectric effect, an electric current is produced in the photodiode. The BH1750 sensor consumes a very low amount of current and is easy to interface with microcontrollers using the I2C communication protocol.
Block Diagram of BH1750
The block diagram of the BH1750 shows a photodiode used to sense ambient light and transfer the sensed signal to an operational amplifier (OP-AMP).
The OP-AMP converts the photodiode current into a voltage signal. This analog voltage is then converted into 16-bit digital data using an internal Analog-to-Digital Converter (ADC). The digital data is processed using internal logic and communicated through the I2C bus interface for ambient light calculation.
Internal Blocks
- Photodiode: Detects ambient light intensity
- OP-AMP: Converts current into voltage
- ADC: Converts analog signal into 16-bit digital output
- Internal Oscillator: Typical frequency of 320 kHz, used as a clock for internal logic
BH1750 Registers
- Data Register: Stores ambient light data.
Initial value: 0000 0000 0000 0000 - Measurement Time Register: Stores measurement time settings.
Initial value: 0100 0101
Pin Configuration of BH1750
| Pin No. | Pin Name | Description |
|---|---|---|
| 1 | VCC | Power supply pin (2.4 V to 3.6 V) |
| 2 | GND | Ground pin, connected to circuit ground |
| 3 | SCL | Serial Clock Line for I2C communication |
| 4 | SDA | Serial Data Line for I2C communication |
| 5 | ADDR | Device address selection pin when multiple sensors are used |
Applications of BH1750 Sensor
- Used in pulse sensors to measure LED light intensity
- Used in mobile phones to adjust screen brightness automatically
- Used in vehicles for automatic headlight ON/OFF control
- Used in automatic street light systems
- Used to control keyboard backlight brightness in smartphones
Conclusion
The BH1750 is a reliable and low-power ambient light sensor that provides accurate digital light intensity measurements. Its simple I2C interface and high resolution make it ideal for applications such as automatic brightness control, smart lighting systems, and energy-efficient electronic devices.