Thymio and the RGB colours


This page includes the script of the video. Sentences in italics are those presented in the clip


Opening credits

Questions about Thymio

  • Thymio can display 35'937 different colours… How is it done?

General concept presentation

  • 1st view
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* Explain the primary, secondary and tertiary colours
* All colours come from basic colours called primary colours. If we mix these primary colours together, we get secondary colours. And if we mix the same quantity of a primary and a secondary colour, we get a tertiary colour.
* Difference between additive and subtractive colour
* Colours can be mixed in different ways: either we add colours together or we subtract colours from each other. The results are called additive colours or subtractive colours respectively.
* Additive colours are used in screens and projectors, but also in our robot Thymio. The basic colour for this colour synthesis is black, when all lights are turned off. When we subtract colours, we remove them from the basic colour white. Subtractive colours are used with paint, where we absorb colours from the white sheet of paper we paint on.
* We are now going to illustrate these different colour systems.

  • 2nd view
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* Subtractive colour (paint)
* Primary colours
* For the subtractive colours, the primary colours are yellow, cyan and magenta.
* Secondary colours
* If we mix these basic colours two by two, we get the secondary colours. If we mix yellow and cyan, we obtain the colour green; if we mix yellow and magenta, we obtain red and if we mix cyan and magenta, we get blue.
* All primary colours added together
* We can also observe that if we mix all three primary colours together (yellow, cyan and magenta), we will get the colour black. Those are the specifications of subtractive colours.

Concept presentation with Thymio

  • 1st view
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* Additive colour (Thymio)
* Let's illustrate the additive colours with our robot Thymio.

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  • 2nd view
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* Show the LEDs in detail and the result on Thymio on a shared screen
* Thymio's colours are a result of a mixture of LEDs. We can see this mixture when we observe the whole of Thymio. As we can see, Thymio's plastic shell diffuses the light.

  • 3rd view
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* Zoom on a "triple LED"
* Let's observe what is happening inside Thymio. Each LED is composed of three small LEDs next to each other (the 3 primary colours) that can be turned on independently of each other.
* Primary colours
* For the additive colours, the primary colours are blue, green and red. We can note that these were the secondary colours that we obtained with the subtractive colours.
* Secondary colours
* To get the "ideal" secondary colours, we must mix 2 primary colours having the same intensity, which means that we need to turn on 2 LEDs with the same intensity. If we mix green and red, we get yellow; if we mix green and blue, we get cyan and if we mix blue and red, we obtain magenta.
* We can also get many different shades if we vary the LEDs' intensities. That is why Thymio can show 35'937 different colours!

* All primary colours added together
* However, if we mix all three primary colours at equal intensity, that is red, green and blue, we will see white light.

  • 4th view
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* Zoom-out from open Thymio to closed Thymio

Conclusion

  • Thymio + sheet of paper with paint
    • Now that we understand how colours are formed, we can say that in both cases the primary colours are the secondary colours of the other formation type and vice versa.

Closing credits

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