The Si1133 from Silicon Labs is an Ultraviolet & Ambient Light sensor is operated and controlled through registers accessible using i2c protocol / two wire interface to initiate on-demand UV or Ambient Light measurement. This sensor has integrated photo-elements array, used to sense the light intensity in wide spectrum range, including the IR, visible & Ultra Violet (UV) (UV Wavelength A at range of 315~400 nm) & (UV Wavelength B at range of 280~315 nm) The 2 integrated 23bit A/D converter can be switched to sample any of the photo-sensing element type, allowing measurement under various light conditions and a wide dynamic range. The user is able to select between several light sensing configurations, to accommodate for LOW/HIGH intensity conditions.

The sensing elements also include black photo-sensors used to provide readings of the dark current. The dark current is the current that flow through the photo-sensors in absence of light. For obtaining an accurate and improve accuracy and sensitivity of the ADC (Analog to Digital Conversion’s) can be set to measure dark current to be subtracted from the final result of the UV measurement. The low-intensity measurement can be also acquired by adjusting the integration time. Typically, the integration time is 24. 4 µs, but by increasing this time, it is possible to sense the light intensity down to 100mlx. Measuring the visible light and near-human eye response, the infrared spectrum component needs to be removed from the measurement. The Si1133 sensor allows you obtain visible IR light spectrum to be read on separate channels, allowing external signal processing.

This Si1133 can also be place to an autonomous operational state where it performs measurement at set intervals and interrupts the host either after each measurement is completed or whenever a set threshold has been crossed. This result in an overall system power saving allowing the host controller to operate longer in its sleep state instead of polling the Si1133. The Si113 can be used in Clinical Lab, Environmental Equipment’s, Mobile & Wearable Devices, Display Back-lighting Control, ALS or UV measurement applications devices, and some various consumer electronics that received ambient or UV light. For more technical detail refer to the datasheet below.

Required Components

  • Arduino IDE | Atmel Studio | Energia | Processing
  • Arduino PRO, FIO, NANO, UNO, MINI, MEGA, PRO MINI, LEO, BT, DUE, ETHERNET,LILYPAD, NodeMCU, Teensy Board, TeensyDuino, ESP8266 12, 12E, ESP32, LinkItOne, ESP8266 NodeMCU, ESPDuino, ATMEGA328 16/12, ATMEGA32u4 16/8/ MHz, ESP8266, MSP430 ,ATMEGA250 16 MHz, ATSAM3x8E, STM32.
    • Note: For AVR (If your using AVR please see the flash size of the MCU)
    • Note: The Diagram below is using NANO. (please refer to each MCU’s respective pin-outs & bus configurations)
  • Si1133 Sensor / Module
  • Capacitors (See below required value)
  • Resistors (See below required value)
  • PCB Designer (Circuit simulation to PCB Layout)

Wiring Guide

Source Code


Wiring Si1133 i2C Ultraviolet / Ambient Light sensor
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