GY-302 BH1750 Light Intensity Module

🧠 What is it?
The BH1750 Light Sensor module (GY-302) is a digital sensor used to measure ambient light intensity in units of lux.
👉 It’s commonly used in systems that need to adjust brightness automatically, like smartphones or smart lighting.
⚙️ How It Works
The BH1750 sensor detects light using a photodiode
Converts light into electrical signals
Internally processes it and outputs a digital lux value
👉 Unlike analog LDRs, it directly gives accurate lux readings (no ADC needed)
🔌 Communication Interface
The module uses the I2C protocol.
Pins:
Pin
Function
VCC
Power (3.3V – 5V)
GND
Ground
SCL
Clock line (I2C)
SDA
Data line (I2C)
ADDR
Address select
🧠 I2C Address
Default address: 0x23
If ADDR pin is HIGH → 0x5C
👉 Allows connecting multiple sensors on same bus
📊 Key Specifications
Measurement range: 1 – 65,535 lux
High resolution: 1 lux
Built-in ADC (16-bit)
Low power consumption
Wide voltage support
🔄 Working Process
Sensor detects ambient light
Converts light → electrical signal
Internal ADC processes signal
Outputs lux value via I2C
Microcontroller reads and uses data
🚀 Applications
📱 Automatic screen brightness control
🏠 Smart home lighting systems
🌱 Greenhouse light monitoring
🛣️ Street light automation
📸 Camera exposure control
✅ Advantages
Direct lux output (no calculations needed)
High accuracy and resolution
Easy I2C interface
Low power usage
Better than LDR for precision
⚠️ Limitations
Not ideal for detecting specific light wavelengths
Slight delay in measurement
Requires I2C support
🔌 Basic Arduino Connection
VCC → 5V
GND → GND
SDA → A4 (Arduino Uno)
SCL → A5 (Arduino Uno)
💡 Example Use
In a smart lighting system:
Sensor reads ambient light
If lux < threshold → turn ON lights
If lux > threshold → turn OFF lights
🔍 Practical Tips
Avoid direct sunlight on sensor for stable readings
Use proper I2C pull-up resistors (often already included)
Place sensor where ambient light is representative
🔁 BH1750 vs LDR (Quick Comparison)
Feature
BH1750
LDR
Output
Digital (lux)
Analog
Accuracy
High
Low
Interface
I2C
ADC required
Calibration
Minimal
Required