SKU: TH2043
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Adafruit LTR-303 Light Sensor - STEMMA QT / Qwiic is a simple, low-cost I2C ambient light sensor breakout designed for reliable light measurements across a wide range of conditions. It provides 16-bit readings for both Infrared and Visible+IR channels, letting you estimate human-visible light by subtracting the IR component from the combined reading.
With configurable gain and integration time, the LTR-303 can cover a broad measurement range from 0.01 lux to 64k lux. That makes it useful for projects such as automatic display brightness control, day/night detection, and light-seeking robots.
This breakout is built in Adafruit's STEMMA QT form factor with onboard voltage regulation and level shifting, so it can work with both 3.3V and 5V microcontroller platforms. It also includes Qwiic-compatible connectors for quick I2C hookup without soldering. QT cable is not included.
Technical details for the Adafruit LTR-303 Light Sensor breakout.
| Brand | Adafruit |
|---|---|
| Sensor | LTR-303ALS-01 |
| Interface | I2C, up to Fast Mode 400kbit/s |
| I2C Address | 0x29 (fixed, cannot be changed) |
| Resolution | 16-bit effective resolution |
| Light Range | 6 dynamic ranges from 0.01 lux to 64k lux |
| Package | Ultra-small ChipLED package |
| Features | Built-in temperature compensation, low active power consumption with standby mode, interrupt output capability |
| Optical Characteristics | Close to human eye spectral response, immunity to IR / UV light source, automatic 50 / 60 Hz lighting flicker rejection |
| Operating Temperature | -30 C to +70 C |
| Compliance | RoHS and Halogen free compliant |
| Board Compatibility | 3.3V and 5V systems via onboard regulator and level shifting |
| Connector Ecosystem | STEMMA QT / SparkFun Qwiic compatible |
Supported with CircuitPython and Python, including Raspberry Pi setups. It can also be used from a full-sized computer with an MCP2221 breakout, and Arduino users can work with the Adafruit LTR-303 library and example sketches.
The breakout exposes the main power and I2C connections, plus interrupt functionality for threshold-based alerts.
| Pin | Name | Function |
|---|---|---|
| 1 | VIN | Power input for the breakout. Use the same logic-level supply as your microcontroller. |
| 2 | 3V | 3.3V output from the onboard regulator, available for light external use. |
| 3 | GND | Ground reference for power and logic. |
| 4 | SCL | I2C clock line. |
| 5 | SDA | I2C data line. |
| 6 | IRQ | Interrupt output for alert or threshold-triggered events. |
Compared to the closely related LTR-329, the LTR-303 adds interrupt/IRQ support. That means your controller can respond only when light levels cross configured thresholds, which is especially useful in low-power designs where you want to avoid constant polling.
The I2C address is fixed at 0x29 and cannot be changed. If you are planning to use multiple identical sensors on the same bus, keep this in mind during system design. Also note that the board supports solderless connection through STEMMA QT / Qwiic, but the QT cable is not included.
It uses an I2C interface and supports Fast Mode up to 400 kbit/s. The sensor's I2C address is 0x29, and this address cannot be changed.
Yes, the breakout includes an onboard voltage regulator and level shifting so it can be used with both 3.3V devices like Raspberry Pi or Feather boards and 5V devices such as Arduino. It also supports STEMMA QT and SparkFun Qwiic I2C connections.
The LTR-303 offers 16-bit effective resolution and six dynamic ranges from 0.01 lux to 64k lux. It measures both Infrared and Visible+IR channels for wide-ranging light sensing.
The main difference is that the LTR-303 adds alert and interrupt/IRQ capability, allowing a pin to trigger when readings cross set thresholds. If you do not need interrupt output, the LTR-329 is otherwise described as basically the same sensor.
Not necessarily. The board has STEMMA QT / Qwiic-compatible connectors for solderless I2C hookup with a compatible cable, and it also breaks out the pins to standard 0.1 inch (2.54 mm) headers for breadboard or wired connections.
Common uses mentioned for this sensor include automatic display brightness adjustment, detecting day versus night, and helping a robot move toward brighter areas. Its interrupt feature can also help in low-power designs by reducing the need to constantly poll the sensor.
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SKU: TH2030
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