Micro:bit Spectrometry

In memoriam Joseph von Fraunhofer, the inventor of the spectroscope.

This basically is a simple combination of two ideas from my previously released instructables. I would have liked to add this to the rainbow contest, but I had to wait some days to long for sunshine.

The micro:bit is a nice device to learn programming, but can also be used to build simple but functional devices. I had previously described a simple colorimetric device consisting of a micro:bit and the enviro:bit by Pimoroni.

A prism was used to split sunlight into the visible light spectrum and the micro/enviro:bit combination used to "measure" the spectral colors. The light intensity and the intensity of the RGB colors are displayed on the micro:bits' LED matrix. The both left rows give the light intensity (log3 scaling, minimum left top, max right down), the three right rows the R, G and B values (min top, max down).

Colors as cyan, yellow, orange will give "mixed" values but the pure colors blue, green and red give high corresponding R, G and B values. The device also allows the determination of precise RGB values, as shown previously.

A micro:bit

Pimoroni enviro:bit

Pimoroni power:bit (or another power source for the micro:bit)

The script for the micro:bit had been described in a previous instructable and attached here

A glass prism, 30 x 30 x 100 mm

A bit of sunshine

A room with a window

The details how to setup the micro:bit had been described here.

The prism was place on the windowsill so that the spectrum was projected to a wall on the other side of the room. Then the micro/enviro:bit was moved through the spectrum, documenting the patterns on the display for several colors. You may use color filters to eliminate certain colors from the spectrum, as described here.

So how does it work?

The prism splits the white sunlight into the individual colors that are projected to slightly different locations, depending on the wavelength, resulting in the spectrum. As the RGBW sensor on the enviro:bit is much smaller then the projected spectrum, this allows to pick individual colors by correct positioning of the sensor. Other then classical spectrometers, where just the light intensity of a selected narrow part of the spectrum is measured, we here get a combined color (RGB) and intensity information. So you might use the setting also to measure emission spectra, e.g. of LEDs or sodium lamps, at least in theory.

For some more theory, please have a look on the Wikipedia articles on spectroscopy and spectrometers.

Above you see a series of images, where I used the device to the spectral colors.

Have a look on the colors and the corresponding patterns/values on the LED matrix.

I also listed them here:

Color R G B

violet 2 2 3

blue 2 2 4

green 2 3 2

yellow/green 2 3 1

yellow 3 3 1

orange 3 2 1

red 4 2 2

baseline 3 2 2