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