The 'Trickle' hand-held controller

A TAFE project was to design and build a hand-held controller with:

a battery hatch
a split line
a power switch
three identical buttons
an LCD screen and
a bend.

Being a workshop based unit, the design itself was less important than the accurate construction of the model. Once the design was locked-in, that's what you had to make. With this in mind (then) fellow student and Team Trajectory stalwart, Steve Wallace suggested the use of his small CNC router. The device was originally purchased to cut tracks into PCBs, but Steve's nothing if not a lateral thinker. It sounded like a great time-saver, too.

After roughing out a few sketches a design was selected and developed. Then I needed to come up with .dxf file for the CNC router. I was doing a manual drafting unit with Ren Jakovich, so I had no excuses for not getting the information across, but I had to learn a bit of AutoCAD before I could get any further.

The outer shell was to be made out of 12mm MDF with a 1mm acrylic spacer to create the split line. Steve's machine wasn't going to accept 12mm thick material so under Steve's supervision I cut a couple of templates out of 3mm MDF.

It wasn't quite as straight-forward as I'd imagined. Load the file, stick the wood in and drink coffee while the machine did my bidding? Not quite. The CNC router controlling application (ISOPro) accepted the .dxf files and then converted them to .iso files. We were using a 3mm cutting tool so the centre line of the cut had to move 1.5mm and it needed to know which areas were waste material (the green areas in the photo above).

A few other oddities, several hours and two broken cutting bits later (dang nails...), I had the templates for the shell and also a 'master' to cast the buttons.

To make three identical buttons, Richard Dann suggested casting them in silicone. Taking the CNC router path meant that I didn't need to cast the same button three times, but could cast them as a set. Thanks Steve!



Armed with the templates I was able to use the table router to copy the shapes and to cut radii. Steve's CNC router was ideal for cutting a recess into the back of the front panel to accept the yellow silicone buttons.

The main components were screwed together so that the angled cuts could be made.

Meanwhile I had to create the 'battery cover'. Conveniently, there was aluminium rod of the right diameter in the workshop, so all I had to do was file a face flat, cut the coin-notch into it with a Dremel and cut a slice off. It was good luck rather than good judgement on my part, but Richard Dann (and Mick Doyle in the Studio unit) had already spoken about working with the dimensions of raw materials.

It sounds a bit like 'cheating' to let materials 'dictate' designs, doesn't it? Would you make sandwiches out of house-bricks, because that's what you had? Probably not; you'd get some bread. Would sliced bread from the bakery come into your plans? Probably. Turkish bread? Maybe, but then sandwich bags, lunch boxes and side plates aren't as much help around these parts. Get clever: know the standard sizes and let them work for you if they can. Don't be the guy who made the arbitrary decision to use 10mm thick sections and had to take 2mm off the available materials to get it. Too late to change the drawing - but a lesson learnt.

Do you wonder why the battery hatch diameter happens to be the same as a standard alloy rod size? Measure a few utility items (that somebody once had to make an appearance-model of) and standard metric or imperial sizes will jump out at you. The battery hatch on my 'designed in California' wireless Mac keyboard happens to be 5/8 of an inch. You can almost see Wynona or Randi in the Apple Design Department sketching the keyboard with a hardware catalogue open. Richard knew this; anyone who didn't wasn't going make the same mistake again.

I was a little concerned about gluing the (now separated) screen and button sections back together to create the 'bend'. I started planning a jig to line everything up but the solution was far simpler than I imagined - Eric Schneider to the rescue, again. He pointed out that if I laid the pieces flat with the longer mating edges lined up and put some tape across them, they would fall together when I picked it up; just add glue.

Then squirt some paint at it.

Sometimes I wonder what would happen if Eric collected all the beer I (and other TAFE students) owe him, all at once. But he wouldn't: fleets have been lost in less!