Arduino Lesson #9

Lesson Objective: Create and build a functioning spectrophotometer using Arduino components. Determine the figures of merit for the designed spectrophotometer.

Materials Required:

  • Recycled materials such as carboard tubes, paper, Styrofoam, aluminum foil, plastic or glass bottles.
  • Tape: masking, duct, or electrical tape.
  • Arduino, wires, breadboard
  • Source, analyzer, and detector of choice.
  • Sample of choice.

Hints for students:

  • Make sure you think about the voltage readings coming from your serial monitor. How do these relate to transmittance? How does this relate to absorbance?
  • Consider what wavelength you are going to use as it relates to the sample and the sensitivity of the detector you choose.
  • Consider if you want to include calibration with a blank instrumentally or in your data analysis.
  • Start simple and expand as you get good results. Sometimes it helps to look up schematics of commercial or hoke-built spectrophotometers online, but this isn’t necessary!
  • Consider what sample you will be analyzing. Simple things like Kool-aid are a great place to start!
  • If you want to use a CD or DVD as a diffraction grating, here is a fantastic video that shows you how to remove the foil label.
  • Start by demonstrating the linear relationship between concentration and absorbance. Then work to improve the linearity by altering your instrument design. Then determine figures of merit for your device. Possible figures of merit to determine include: sensitivity, limit of linearity, minimal detectable absorbance, detection limit, limit of quantitation, dynamic range.
  • Above all: be creative, work hard, and have fun!!

Helpful Links:

  • The scene “Square Peg in a Round Hole” from the 1995 Apollo 13 movie can be found here.
  • An excellent journal article explaining the important figures of merit that can be determined from creating an Arduino controlled spectrophotometer.
  • Old non-digital instruments can also be interfaced with Arduinos to modernize the data collected with these instruments. An example of this is the old Spec20 spectrophotometers. This article shows how to interface with the Spec20s. My students were all successful in interfacing and collecting data electronically with our collection of these old, but reliable, instruments!