Milling PCB Cover

I milled out an updated version of the trackball PCB cover today.  It took several hours, but looks good.  Below are some pictures of the finished product and a video I shot at the beginning of the session.

Grounding patch

The grounding patch is finished.  It has two strips of velcro hook sewed on each end of the stretchy conductive fabric.  I secured one side with the velcro, then gave it a stretch over to the other side and tacked the other side down as to make a nice smooth addition to the top.  A wire is connected by crimping force under a metal gromet to connect the fabric to the Teensy board.  In addition to providing a grounding patch, this is where I anticipate most of the wear to be happening, so it can be replaced at a later date without having to replace the whole hand support. 

What is left?  Well, all parts are done and working.  I need to design and mill a new bottom cap on the track ball module as the current one is a little too short.  Once that is done, I'm guessing it is time to start making some silicone molds of these CNC machined parts to be ready to reproduce them and make anther full trackball to prove it can be done.  Once they are reproducable, I'm thinking I'll need to get a few in the hands of alpha and beta testers to see what needs adjusting. 

Showing Off Some Pictures

Over the past few days, I've made quite a bit of progress.  The new hand support is a dream.  I took some time today to tidy up the unit and get it ready for pictures.  Long gone is the bread board and it is a self contained unit.  Some pictures below:

New Hand Support Promising

This afternoon, my wife and I learned how fun it is to sew two pieces of 2mm neoprene material together using a common household sewing machine.  It took a few trys, but eventually we got the tention setup right and learned a few techniques along the way.  4mm of neoprene is taller than the gap under the sewing machines presser foot, so it can be challenging.  The new hand support is done.  It looks and works great.  It is filled with the sand and clay mixture and isn't leaking out.  I couldn't be happier with the way it came out with a solid feel, yet moldable to fit your hand.  The outside is 100% covered in Velro type loop that accepts normal Velcro hook.  I pasted some "industrial strength" Velcro hook on the back of all the buttons and put them on there.  They hold quite nice to the outside of the hand support and allow their removal and  re-installation to the new hand support over and over again until you get each button in exactly the right place.  We went with a very conservative stitch path that is pretty much just a rectangle and straight stitch.  The next version will have a bit more curves and design flare with a zigzag stitch now that we know we can sew it. One of the secrets ended up being the use of tissue paper both above and below the neoprene to help it slip under the presser foot and feed.  The neoprene by itself is quite stubborn and wants to hang up, causing it not to feed through the machine.  Another tip learned is to stick the neoprene parts to be sewn together with double stick carpet tape.  Pinning them together just doesn't work since the material is so thick.

One of these days I'll get around to posting some actual pictures, but my desk is just a mess with all the tools, wires and so on, so I have been reluctant. 

Next up is the creation of the grounding patch that will sit atop the hand support.  I received the small sample size Medtex180 material from SparkFun last week.  It looks and behaves much like regular spandex type material with a nice shiny gleen on one side.  I plan to use a small metal gromet that I bought at the local fabrics store poked through the material and hammered down nice and tight to make a soldering point.  That should make a good solid connection without the requirement of an adhesive.

After the grounding conductive material is in place is to migrate the Teensy board from the breadboard over to its place on the hand support.  I wanted to be sure we got the hand support nailed down before I started figuring out where the Teensy board would reside.  In order to do this, I'll need to design a soldering template that will help me add some tiny 0603 size capacitors to all of the analog pins (11 of them) on the underside of the Teensy board; each run to ground.  Using low value capacitors (100pF - 490pF) really helps make the capacitance touch events much more responsive and repeatable.  While I can reliably detect touches without them, the are a little slower without the capacitors in place.  I plan to glue them down with the hot glue gun to give them structural support to stay attached, in addition to being soldered to each pin the grounding wire running between all of them.  They will all be covered over with a piece of Velcro hook that will hold the Teensy board to the hand support so nobody will know they are there.

Grounding the humans

While troubleshooting some capacitive touch issues today, I discovered a major advancement.  By grounding the human who will be touching the buttons, it makes detecting capacitive touches very much easier as there is a path to ground through the skin.  Looks like I'll be needing to procure some conductive fabric to play with.  As a test, I've just got some bare wires running over the hand support this evening and it is working great.  I read over Jeff's write up over at Keyglove regarding conductive cloth.  I'll need to find a source to get a little.  It doesn't have to be all that stretchy as I'll be sewing it to a piece of velcro.  The end-user will need to just paste it on the hand support somewhere it that it will contact their hand.  The hand support will be made from material with velcro loop, so options are limitless.

Arrival of the Pentabutton

I designed a new "pentabutton" before Christmas and finally got around to milling it out yesterday.  I'll be working on the metal contacts to complete it sometime today.  It should allow me to fully map out all 11 capacitive touch buttons.  Buttons will include:  3 mouse, 2 scroll (up & down), 1 resolution selection, 5 user programmable keystrokes.

The new pentabutton is intended to be placed for your first finger and first mouse button.  The mouse button being in the middle area with four optional programmable button pads around the sides.

On a side note, I'm awaiting the arrival of some neoprene material to make yet another hand support prototype.  Making this thing work from an electrical and programming point of view was the easy part.  Designing the look and feel seems to be the harder part of this project.  I'll be contracting my wife to sew up the neoprene and help me out with the pattern making with her mad sewing skills.