NIME Stage Capacitive Touch Sensors

NIME Stage Capacitive Touch Sensors

March 22, 2018
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I took the capacitive toggle touch sensor from Adafruit and made it so you could use a custom board.  The board to the left is the original.  The board to the right is the modified version with surface mount terminal components for custom capacitive plates and external power and ground.

I then took my board and exported the pdf to Illustrator.  I printed a hard copy to make sure the terminal legs fit these pads and the distance between them.  In illustrator, I inverted the black and white board layout for the lasercutter raster.  I also added labels and things to make my life easier.

For the physical circuit, I sprayed one-sided copper PCB board with oil-based spray paint.  I bought flat spray, but it’s better to use glossy.  You can by Krylon brand spray paint from Blick for this.  The difference between the flat and the glossy paint is that the flat paint has a rough surface which expedites the etching process in covered areas…. this can lead to random holes or exposed areas, so it’s better to use glossy if you can.  After spraying, I etched the board on the lasercutter.  The laser cutting  exposes the copper in the areas that I wanted to etch away in the acid (1st image from the right).  I used 100 percent power and 100 percent speed and ran the cut 3 times to make sure all those areas were completely exposed.  Then I wiped the board down of any paint-ash and dipped it in the acid bath (with Kar’s supervision, 2nd from the right).  In the bath I used a synthetic brush to expedite the etching process.  Once this was done, I used acetone nail polish remover to remove the remaining black spray paint (3rd from the right).  Lastly, I soldered all my components to my board with the solder paste and heat gun (BOM here).

Yay!  Success.

My one thing, was that I didn’t understand the full anatomy of the touch sensor from the original capacitive pad.  The pad was basically a double sided copper plate with power on one side and ground on the other.  Andy and I snapped my original plate and taped the two new pieces back to back… et voilá!

This was the capacitive  toggle.  My next steps will be to make a few more of these and a shit ton of the capacitive momentary for my NIME stage.

 

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