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Adafruit VCNL4040 Proximity and Lux Sensor is a handy 2-in-1 I2C sensor breakout that combines short-range proximity sensing with ambient light measurement on a single board. It can detect proximity from 0 to 200 mm and measure ambient light from 0.0125 to 6553 lux, making it useful for touchless interfaces, presence detection, display brightness control, and general light-aware projects.
The breakout includes onboard support circuitry so it can be used with both 3.3 V and 5 V microcontroller logic levels. Since it communicates over I2C, wiring is simple, and the onboard STEMMA QT / Qwiic connectors make solderless hookup easy with compatible boards and cables.
The VCNL4040 also gives you control over measurement behaviour. You can adjust the ambient light integration time to trade off range versus sensitivity, and tune the IR LED current and duty cycle to change proximity sensing response. Libraries are available for Arduino as well as CircuitPython/Python.
Technical details for Adafruit VCNL4040 Proximity and Lux Sensor.
| Brand | Adafruit |
|---|---|
| Sensor IC | Vishay VCNL4040 |
| Interface | I2C |
| Board Input Voltage | 3 V to 5 V DC via VIN |
| Proximity Range | 0 to 200 mm |
| Ambient Light Range | 0.0125 to 6553 lux |
| Light Integration Time | Adjustable from 80 ms to 640 ms |
| Connectors | STEMMA QT / SparkFun Qwiic compatible |
| Software Support | Arduino, CircuitPython, Python |
Key connections available on the breakout board.
| Pin | Name | Function |
|---|---|---|
| 1 | VIN | Power input for the breakout board, accepts 3 V to 5 V DC |
| 2 | 3Vo | Regulated 3.3 V output from the onboard regulator |
| 3 | GND | Common ground |
| 4 | SCL | I2C clock line |
| 5 | SDA | I2C data line |
| 6 | INT | Interrupt output for configurable proximity or light threshold events |
QT cable is not included. The board uses STEMMA QT / Qwiic compatible connectors for quick I2C hookup.
Important: the VCNL4xxx family includes several similar-looking parts, but their firmware and libraries are not interchangeable. You cannot simply swap a VCNL4030 and VCNL4040 without using the correct library or recompiling code as needed.
This breakout includes pull-up resistors on the I2C lines, so external pull-ups are typically not required.
It combines two functions in one board: proximity sensing from 0 to 200 mm and ambient light sensing from 0.0125 to 6553 lux. This makes it useful for short-range object detection and lux measurement in the same project.
Yes. The breakout includes onboard support circuitry and a regulator so it can be used with 3.3V boards like Feather or Raspberry Pi as well as 5V boards like Arduino or Metro.
It uses an I2C interface, so you connect power, ground, SDA, and SCL. The board also includes STEMMA QT / Qwiic-compatible connectors for quick plug-and-play I2C wiring.
No. The supplier brief specifically notes that the QT cable is not included.
Yes. Adafruit provides driver support for Arduino as well as CircuitPython/Python, so it can be used with supported microcontrollers and host systems over I2C.
No. Adafruit notes that VCNL4xxx sensors may look similar, but their firmware and libraries are not identical, so swapping between models like VCNL4030 and VCNL4040 requires the correct library and code changes.
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