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Rainbows, natural phenomena that produce beautiful spectrums of coloured light in the sky, inspire myth and legend and art and give happiness to millions of people. Just as natural rainbows are created by how sunlight plays through water droplets in the atmosphere, we can artificially create our own rainbows using prisms. There are many scientific applications of rainbows, and one is ‘Spectrophotometry’!
A spectrophotometer is a scientific instrument used to measure how different wavelengths of light (the different colours of light seen in the rainbow are different wavelengths) are absorbed by a sample. This analysis can tell us all sorts of things, and these instruments (first made in the 1940s) have played a huge role in modern science, especially biochemistry.
In this Instructable, we’re going to make a basic Arduino-powered spectrophotometer, using a little prism to create and use our own rainbow. We’ll make a lot of use of 3D printing, and also learn about lots of other things along the way.
The project video gives a short overview of the project, but please read on through the Instructable for full instructions too!

These are the components I used to build my prototype. Please read onto the next step to read a more full explanation of how a spectrophotometer works, and how we can make our own at home!

Main Components

- Triangular prism (30mm each side)
- Arduino Uno
- LDR (light dependent resistor)
- 16-Bit LED pixel ring
- 9g Servo
- Mini Test Tubes
- DC-DC boost converter 5V-9V
- USB cable (one end cut off, and the power lines soldered to the boost converter)
- Wall plug that can supply 5V DC 0.5A
- USB cable to connect Arduino to PC

Minor Components

- Ball bearings
- Toggle switch
- Momentary push button
- E10 filament light bulb
- Bulb holder
- 10k ohm potentiometer (or larger)


- Heatshrink
- Header pins
- Hookup wire
- Solder
- Electrical insulative tape
- 3D printing filament


- Windows PC
- 3D printer (my print bed is 210x210mm)


- Arduino IDE
- CAD Software if you want to modify the files and view the assembly”

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