The Crystal Cave


It had been a hard week so a trip to the Adam and Eve Inn was in order. Hans and Matilda sat next to the dwarves who for once were not having an argument. The dwarves had recently discovered a new cave lined with amethyst and citrine crystals, they discovered a strange phenomenon that happened on a full moon. Tonight was a full moon so Hans and Matilda were invited to see. They were given hard hats with lights and headed off through the forest to the mine. As they journeyed a wolf howled in the distance. They arrived at the mine and headed into the tunnels. After several turns and forks they arrived at the new workings, "23m below ground" the dwarves told them. As they rounded the corner they were met with purple and yellow twinkles as their torches shone off the mineral deposits. The dwarves told them to find a comfortable place to sit and one by one all of the torches were distinguished. Hans nervously held Matilda's hand, he was not used to such extreme darkness. Matilda on the other hand found it calming and smiled in Hans' direction. Suddenly, light appeared from above, it got rapidly brighter until the whole cave was glowing, it was a magnificent sight. Then as suddenly as it appeared the light faded away. "It happens each day when the sun is overhead" explained the lead dwarf, "but it's better with a full moon as the light is softer". He pointed his torch to a hole in the ceiling, the light reflects of the internal walls of that shaft and bounces all the way down here to the cavern".


Extending the LEDs with fibres


Matilda realised that this idea of total internal reflection was also how fibre optics works, she wondered if these could be used to extend the LEDs that were deep in the heart of the electronics to the top of the house for display. Some fibres were purchased and Matilda played with bundles of these wrapped in tape to ensure that the light would transmit as desired.


She designed a part to fit over the LEDs on the Arduino Yún with slots to take fibres from the LEDs

Fibre Housing R1

The first version of this was printed and had a couple of issues. One of the corners badly distorted where the adhesion to the bed was poor, the second was that the holes were too small so installing the fibres would be challenging. An additional check showed that the holes for the support struts were a bit small so these were increased from 3.2mm to 3.7mm.

Fibre Housing R1 Printed

The new model resolved these issues with bigger slots for fibres, bigger holes and the sharp corners were chopped off.

Fibre Housing R2

That fixed the problems and the new part printed without issue.


A top panel for a couple of switches and 4 lights was also designed, the POWER, WIFI, LED 13 and USB LEDs are to be extended to the panel as all of these can be controlled by our code / hardware.


Top Panel


Testing the fibres


0.5mm fibres were used so that they could be in a straight line for the rectangular LEDs but in a circle on the top panel.



The fibre housing and top panel work well but the fibres are quite slippy (and have a low melting point) so the heat shrink tubing used to indicate the colours and hold the fibres together is not locking them in place. Some kind of adhesive will need to be added, I suspect Sugru will do the trick.

Fibres Top PanelFibres Arduino



Arduino Yún Fibre Housing Design:

Arduino Yún Fibre Housing Model:


Top Panel Design:

Top Panel Model:




Arduino Yun LEDs


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