BH1750 Light Sensor: Raspberry Pi

1. Introduction

The BH1750 is a digital light sensor that measures ambient light intensity in lux. Unlike LDR, it provides direct digital output via I2C, making it accurate and easy to use with the Raspberry Pi.

2. Components

Raspberry Pi 4 Model B
BH1750
Jumper wires
Breadboard (optional)

3. Circuit and Connections

Raspberry Pi Pinout Diagram

BH1750 Light Intensity Sensor Pinout Diagram

I2C Connection Table

BH1750 Pin	Raspberry Pi
VCC	3.3V
GND	GND
SDA	GPIO2 (Pin 3)
SCL	GPIO3 (Pin 5)

👉 Default I2C Address: 0x23 (or 0x5C depending on ADDR pin)

4. Detailed Step By Step Circuit Working

BH1750 senses ambient light intensity.
Internal ADC converts light into digital lux value.
Data is sent via I2C protocol (SDA & SCL).
Raspberry Pi reads lux value directly.
No external ADC required.

5. Libraries to be Included

Install required libraries:


sudo apt update
sudo apt install python3-smbus i2c-tools
pip3 install smbus2

Enable I2C:


sudo raspi-config

→ Interface Options → I2C → Enable

6. Code (Python)


import smbus2
import time

bus = smbus2.SMBus(1)
addr = 0x23

while True:
    data = bus.read_i2c_block_data(addr, 0x20)
    lux = (data[0] << 8 | data[1]) / 1.2

    print("Light Intensity: {:.2f} lux".format(lux))
    time.sleep(1)

7. Detailed Step By Step Code Working

SMBus(1) → Initializes I2C bus
addr = 0x23 → Default BH1750 address
read_i2c_block_data() → Reads sensor data
Combines two bytes → gives light value
Dividing by 1.2 → converts to lux
Loop continuously prints light intensity

8. Tips

Use i2cdetect -y 1 to confirm address
Avoid direct strong light for testing
Use stable 3.3V supply
Keep wiring short
Try address 0x23 / 0x5C if not detected

9. Uses

Automatic street lighting
Smart home lighting systems
Display brightness control
Weather monitoring systems
Energy-saving applications

10. Conclusion

The BH1750 is an accurate and easy-to-use digital light sensor. With I2C communication, it simplifies light measurement projects and eliminates the need for ADC.