The GA1A12S202 is an analogue light sensor with a logarithmic response across a wide dynamic range of 3 to 55,000 lux. Unlike standard photocells that are either too sensitive in bright light or not sensitive enough in the dark, this sensor provides useful readings across both indoor and outdoor conditions without changing code or calibration.

The breakout board includes a 68 kΩ resistor to convert the sensor's current output to a voltage. Simply connect power, ground, and read the analogue output — it ranges up to 3 V in extremely bright sunlight. On an Arduino, use analogRead() on the OUT pin.

Key Features

• Logarithmic Response – True log-linear relationship with light levels
• Wide Dynamic Range – 3 to 55,000 lux
• Analogue Output – No microcontroller required for basic use
• Consistent Calibration – Chip-fabricated sensor with minimal unit-to-unit variation
• Indoor/Outdoor Use – Works in dim and bright conditions without adjustment

Specifications

• Sensor – GA1A12S202
• Input Voltage – 2.3–6 V DC
• Output – Analogue voltage, up to 3 V
• Light Range – 3–55,000 lux
• Load Resistor – 68 kΩ (onboard)

Ideal For

• Ambient light measurement
• Automatic display brightness adjustment
• Indoor/outdoor light level monitoring
• Replacing photocells in existing projects