Educational Colorimeter Kit

Colorimeters are analytical devices commonly used in science labs to measure the amount of light of a specific wavelength that is absorbed by a sample. Absorbance is related to concentration (Beer-Lambert Law) so the greater the concentration (color intensity) of a sample, the greater the absorbance (A) value. Comparison of the absorbance measurements to a calibration curve provides the final concentration in the sample. In this project we have designed an open source colorimeter with an Arduino shield.

The colorimeter e ssentially consists of two electronics boards: i) a red-green-blue (RGB) LED board and a light sensor board. A cuvette holder in the center of the colorimeter properly positions the sample between the LED and the sensor. The sensor board connects to a Arduino programmed with the colorimeter firmware via a simple colorimeter shield. When the colorimeter is operating, the RGB LED illuminates the sample in the cuvette with one of three different wavelengths of light:

	Peak wavelength	Dominant wavelength	Intensity	Spectral bandwidth
Red Light	632 nm	625 nm	1077.5 mcd	18 nm
Green Light	523 nm	528 nm	1570 mcd	33 nm
Blue Light	465 nm	470 nm	377.5 mcd	25 nm

A small slit in the colorimeter allows light to pass through the sample to the light sensor. Absorbance (A) of the sample is determined by comparing the intensity of incident light (I₀) to the intensity of light after it has passed through the sample (I) using the following equation: A = log₁₀(I/I₀). Check out the User Guide for more background information.

Getting started with the educational colorimeter kit

The Educational Colorimeter Kit (SKU # COLOR-01) contains the following items in a 6" x 4" x 3" clear storage container:

Colorimeter LED board;
Colorimeter sensor board;
Colorimeter shield for the Arduino;
12 laser cut acrylic parts;
Hardware for the enclosure (20 screws, 8 nuts and 6 standoffs);
4 x pre-crimped colored wires and housing;
Ribbon cable for connecting the Arduino and colorimeter shield;
Set of 6 cuvettes;
Philips head mini-screwdriver.

You can also choose to include an Arduino Uno along with the kit if you do not already have access to one. Once you have the colorimeter kit, follow these 3 steps to get started:

Step 1: Assembly

Assembly takes approximately 20-30 minutes and instructions can be downloaded here or from the User Manual. Note that the kit does include a mini-screwdriver and all of the boards are already assembled so no soldering is required.

Step 2: Programming the Arduino

(Note: If you ordered a pre-programmed Arduino with your colorimeter kit, you can skip this step).

Download the latest version of the firmware from here onto your computer. Unzip the downloaded file to a known location. After unzipping you should see a "colorimeter_firmware" folder containing the files used by the firmware. Connect your Arduino board to the computer, launch the Arduino IDE (Installation instructions available at http://arduino.cc/en/Guide/HomePage) and open the main firmware file "firmware.pde". This file should compile without needing to download additional libraries. After selecting the Arduino board model and the serial port (under "Tools" menu of the Arduino IDE), upload the firmware to the board.

Step 3: Downloading the colorimeter software

Download the software for your choice of Operating System (Windows, Mac or Linux) from the software page. The files are provided as precompiled binaries so they can be launched immediately after download (by double-clicking on any of the 3 program files). For the more adventurous users, the source files are available at http://bitbucket.org/iorodeo/colorimeter. The software suite we have developed consistes of 3 different programs:

Colorimeter Basic Program: This program reports the Transmittance and Absorbance measured by the colorimeter for the wavelength(s) of light selected by the user.
Colorimeter Plotting Program: This program can be used to generate calibration/standard curves that can be used to determine the concentration of a solution.
Colorimeter Concentration Program: This program measures the concentration of an unknown solution.

Using the colorimeter

Once assembled, the colorimeter can be used in a huge number of experiments. Some labs and examples are listed below.

Light absorbance with colored solutions - Introductory colorimetry lab using food dyes
Beers Law lab - Use food dye or other colored solution (eg. copper sulphate) to investigate the relationship between concentration and absorbance;
Nitrogen cycle lab - Investigate nitrification bacteria in aquarium gravel
Aquarium water quality tests - Use a chemical assay to quantify the amount of ammonia, nitrite and nitrate in your home aquarium water;
Population growth - Measure the absorbance of a microbial culture over time to follow population growth (lab coming soon).
Measure beer color - Measure absorbance at 430 nm to quantify beer color (lab coming soon).

Calibration Curves

Measurement	Method	Solution color	Absorbance Peak	LED	Range	Calibration data
Ammonia	Ammonia-Salicylate Assay	Green-Blue	660 nm	Red	0 - 2.5 ppm	ammonia_salicylate.txt
Ammonia (saltwater samples)	Ammonia-Salicylate Assay			Red	0 - 2.5 ppm
Ammonia - API test kit (updated)	API ammonia test kit	Green	686 nm	Red	0 - 8.0 ppm	ammonia_api.txt
Erioglaucine (Blue food dye #1)	Not applicable	Blue	630 nm	Red	0 - 14 uM	erioglaucine.txt
Erythrosin B (Red food dye #5)	Not applicable	Pink-Red	526 nm	Green	0 - 14 uM	erythrosin_b.txt
Iron	Hach FerroVer Reagent Pillow		510 nm	Blue	0 - 10 ppm	iron_hach.txt
Nitrate	Nitrate Reductase & Greiss Assay	Purple/magenta	540 nm	Green	0 - 45 ppm	nitrate_nr.txt
Nitrate - API test kit (updated)	API nitrate test kit	Red	545 nm	Green	0 - 200.0 ppm	nitrate_api.txt

colorimeter

Thank you to all of our Kickstarter Backers for helping us to reach our funding goal and for supporting development of the open source colorimeter project !