This project details an open-source colorimeter, which is made from open source electronics and 3-D printable components. This is part of a larger project to reduce the cost of scientific equipment using open-source hardware.
Colorimetric analytical methods are likely to be the most commonly applied methods for determining the concentration of dissolved species. Many dissolved species absorb light of a particular wavelength and the amount absorbed as the light passes through a given length of solution increases with increasing concentration the species; higher concentrations absorb more light than do lower concentrations. The relationship between absorption and concentration is defined by the Beer-Lambert law:http://en.wikipedia.org/wiki/Beer-Lambert.
A colorimeter or a spectrophotometer is employed to measure absorption at a specific wavelength. Light is usually filtered to permit only a narrow band of light at the absorbance peak wavelength for the species measured. The apparatus typically reports results in concentration units but also reports absorbance units or transmittance.
This new Adafruit shield makes it easy to use a 16×2 Character LCD. We really like the Blue & White 16×2 LCDs we stock in the shop. Unfortunately, these LCDs do require quite a few digital pins, 6 to control the LCD and then another pin to control the backlight for a total of 7 pins. That’s almost half of the pins available on a classic Arduino! With this in mind, we wanted to make it easier for people to get these LCD into their projects so we devised a shield that lets you control a 16×2 Character LCD, up to 3 backlight pins AND 5 keypad pins using only the two I2C pins on the Arduino!