Tuesday, October 4, 2011

Capacitive Touch Fine Tuning

I spent most of the last 3 days working through the finer points of the capacitive touch buttons.  While they were working, they would pulse on and off randomly, making it impossible to drag anything while holding down a mouse button.  I now have a very solid, responsive system working with 4 buttons (right, middle, left and resolution).  It took quite a bit of fine tuning to be both reliable and responsive so I can still easily double-click.  I had to formulate an averaging algorithm that samples each button and keeps a rolling average to get the genaral idea if someone is touching the button or not.  It works really well.  Apparently the capacitance draw of a person isn't very stable.  It's so nice to have a totally silent trackball system with just the ball as the moving part.  "Clicking" (or touching in this case) is lighting fast.  I've been using the new one to browse the web more than the other one lately, though it is currently a two hand arrangement with buttons on left hand and trackball on right hand.  It'll be sweet once it is all integrated.

I'm gearing up to finish up on the ball support, version 4.  It will be double tall this time and have a bottom cap mated up to cover up the circuit board.  I had to order some special #2 screws as the local hardware stores don't carry little stuff like that.  They will be in tomorrow.

Silicone is on order for the hand support.  I plan to rotocast that into a thick silicone balloon of sorts, then fill that with semi-wet sand.  That'll be covered partially with velcro to arrange the buttons around. 

The ball support will need double-sided milling, so working through the front-side and back-side registration with MeshCAM.  I think I have it worked out, but we'll see...

The new ball support design and smaller screws means I'll need to re-mill and make the circuit board.  I scored some soldering paste from a relative in the electronics business and I'll be using my toaster oven I bought a few years ago when I first planned to be making circuit boards.  I probably should get a proper thermocouple setup going to be a little more accurate on the heating....one of these days...

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