Thursday, November 27, 2014

A Sophisticated Heat Beam Which We Called a "Laser."

Having recently acquired a stylish collection of potentiometers and knobs from Tayda2009, I wanted to mount them in a mechanically solid way. An excellent opportunity to learn how to use the Epilog laser cutter at FabLab Z├╝rich

I started with a box design built at MakerCase, rearranged the pieces to fit an A4 sheet of poplar plywood, and added the other features (cutouts for the potentiometer shafts and wires, outline for the breadboard, etc) to the top surface.

After struggling unsuccessfully with Inkscape (which was not overly fond of the 0.01mm thickness of lines signaling to the laser cutter to cut instead of rasterizing, and created PDFs that omitted all circles with that thickness), I spent a well invested dollar on EazyDraw 3 (there appears to be a separate app for every version from 3 to 7, with prices neatly staggered, which I didn't know when I bought the oldest one, but it was perfectly suitable for my purposes) and redid the SVG, creating a PDF that opened just fine.

15 minutes' or so worth of cutting and rasterizing got me this: 

The design has a number of flaws (a.k.a teaching moments for next time):

  • I left off the bottom surface, because it would have been useless, but I forgot to adjust side surfaces to remove the fingers for the bottom. Oh well, I'll pretend these were meant for ventilation.
  • The box is considerably deeper than it needs to be. 2cm would have been ample, I made it twice as deep.
  • The potentiometers I bought have a little pin at the edge, which I had not noticed. In order to be able to mount them flush, I had to cut small notches for those pins, which luckily was no problem with the plywood.
  • The hole for the wires are a bit close to the potentiometer shaft hole, as the pins of the potentiometer are fairly long. On the other hand, there's no reason why the pins of the potentiometer have to point in any particular direction (the knob will mount in any orientation),   so I might just cut the pin notches so the potentiometers are facing at a 45 degree angle to the wire hole next time.
Overall, though, I'm pleased with the result, shown here demonstrating three simple audio circuits (On the left, a VCO and a Metronome, using the two timers of a 556. On the right, a non-functional attempt to build an OpAmp based circuit driving a piezo element).