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In the first attempt I tried to put the LED halfway up the inside wall taking the wires down the middle of the wall.   Initially the sides were necessarily fairly straight to make it easier to drill the hole.  It worked but I was not happy with the shape and in addition I could not find a way of sealing the LEDs into the side walls with resin.  I don’t have a vacuum chamber or pressure pot so I use clear resin that takes 2 days to cure.  I wondered if I could put it on a turntable and use centrifugal force to keep the resin in the groove until it cured but in the end sensibly, I guess, I abandoned the whole idea.

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Second attempt. I made the decision to put the LEDs as a ring in the base which made the design a lot easier.  The sealing with resin worked fine under gravity and I could shape and polish it to flow with the wood.  I did not need to compromise on the shape of the main part of the bowl as the wiring just dropped down into the base of the bowl.  The issue was then about how to incorporate the electronics into the hollow base. I made the walls too thin initially to try and keep the base not too thick and near the end of the turning it all exploded on the lathe.

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A working version

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With the third attempt I accepted the need to have a bigger base and also tried to reduce the size of the electronic circuitry.  It did however still come off the lathe and the base broke on the floor.  Rather than start again I flattened off the bottom and added another piece of wood.  To hide the join I decided to colour the outside and use gold leaf.  By chance I had watched one of John Clothier’s excellent demos at last years Kempton Park show and he had kindly sent me instructions after the show.  Elsewhere in this newsletter are some details of this technique.

 

The last problem I had was to find a battery small enough and powerful enough to last more than an hour or two, LEDs do take a surprisingly high current.  The solution this time was to use an old phone charger connected externally.  I have been told that maybe a different battery that could be recharged inductively might be a good idea but have no experience of this.      

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Future

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Controlling the lighting effects via a Bluetooth link to my phone was an interesting diversion from the woodturning but all a little unnecessary really.  My next attempt will be to forget the Bluetooth link and the Android app and this will mean the electronics will be a much smaller package – a rotary switch on the bottom should still allow different effects to be chosen.

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The electronics was constructed around an Arduino nano microprocessor, the app was built using MIT Appinventor.  

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Appinventor code below - the Arduino program code is in the Arduino section.

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