Open Colorimeter PLUS Electronics

The Open Colorimeter uses STEMMA QT connectors. Communication with peripheral devices via I2C using 4-wire cables with JST SH connectors, such as  Sparkfun Qwiic or Adafruit STEMMA QT, is rapidly becoming a standard on new development boards. This standardized cabling allows multiple sensors to be connected to the development board without any soldering.  By using these standardized connectors our colorimeter compatibile with the large and growing variety of development boards that support this standard.  For example Adafruit Feather RP2o40FeatherS2Sparkfun Qwiic ProMicroSparkfun RedBoard Qwiic and many others. It will also work with the larger 4-pin STEMMA connectors with a JST PH to JST SH adapter cable  so that development boards such as the PyBadge and PyGamer can be used - both of which are ideal for making standalone instruments. For those wishing to use the Raspberry Pi  a Qwiic HAT adapter is available from Sparkfun.  


  • We are currently using the Adafruit PyBadge, though the PyBadge LC and EdgeBadge are also supported
  • We decided to use the Adafruit PyBadge as our initial target hardware platform. The PyBadge has a 160x128 color TFT display, Lipo battery connector with recharging capability, a 4-pin I2C connector for connecting the light sensor and on/off switch and buttons for user input.  In addition, the PyBadge can run circuitpython making firmware development quick and easy
  • As we described above, the light sensor and LED are connected to the development board via an I2C connection with a standardized STEMMA-QT/Qwiic connector. Thus no hardware changes are required when switching to boards and only very minor changes are required to the firmware in order to accommodate a different screen size.The I2C devices connected via STEMMA-QT/Qwiic connectors are chainable making it easy to modify by connecting to additional sensors and actuators for even more advanced customization!

Dual Light Sensors

Primary measurement sensor (90°)

The Open Colorimeter Plus uses the same measurement sensor as the Open Colorimeter.

Adafruit TSL2591 High Dynamic Range Digital Light Sensor
When the future is dazzlingly-bright, this ultra-high-range luminosity sensor will help you measure it. The TSL2591 luminosity sensor is an advanced digital light sensor, ideal for use in a wide range of light situations. Compared to low cost CdS cells, this sensor is more precise, allowing for exac…

Secondary light sensor (180°)

The 180° sensor we are using is the Adafruit BH1750 Light Sensor - STEMMA QT/Qwiic. This is an inexpensive $4.50 light sensor with STEMMA connectors so it can be easily connected to the Open Colorimeter Plus. The interface to the BH1750 light sensor was added to the CiruitPython firmware using the Adafruit_CircuitPython_BH1750 library. This library is part of Adafruit's CircuitPython library bundle. The latest releases for the CircuitPython library bundle can be downloaded from here.

Adafruit BH1750 Ambient Light Sensor
This is the BH1750 16-bit Ambient Light sensor from Rohm. Because of how important it is to humans an most other living things, sensing the amount of light in an environment is a common place to get started when learning to work with microcontrollers and sensors. Should we turn up the brightness of…

LED boards

Coming soon