Wednesday, February 10, 2010

Emission Spectra

The New Year brings in good things!

When I was learning how to knit, I spent a long time trying to cajole a friend of mine into making me the world's geekiest present: an emission spectrum scarf. It didn't pan out, but over New Years (and over drinks) we were circulating the idea around again and now it looks like Stern Lab is on assignment!

Becky over at Stern Lab is making emission spectrum scarves! Once she starts selling them at her Etsy store, you should go pick one up! Best. Present. Ever.

Fig 1. Silicon


Every Christmas break is another opportunity to go down to Adafruit Industries in NY, NY and (in addition to having a good time) exercise my nascent industrial design impulses. The new tradition is to knock out a kit enclosure. Adafruit's design constraints were as follows:

1. The enclosure needed to be made out of 1/8" acrylic.

2. It would preferably be completely enclosed.
3. She didn't want "just a box."
4. It should have a variable tilt angle to accommodate the viewing angle of the LCD screen.

Until I get a copy of my notes back (which show my entire thought process, including doodles and the Bad Ideas Club) - these photos will have to suffice. I designed everything to slot together because I really like slotted flat-designs (go read Nomadic Furniture 1 & Nomadic Furniture 2 for more fun flat designs and examples of things Frank Gehry was actually good at designing -- PROTIP: It's not buildings)!

Fig 1. Notes 1

Fig 2. Notes 2

Fig 3. Notes 3

Fig 4. My draft enclosure in clear acrylic.

There were a couple of things about my prototype that I knew Adafruit didn't like. I had an asymmetric profile shape - chosen because I based the design off of an isosceles triangle, and a truncated triangular side profile meant I could slot the top piece in for ultimate interlocking action. I also really enjoyed the idea of having a low, flat very Byzantine/monolithic/robots-will-eat-you shape, which made the enclosure larger
than Adafruit's prefs. She ended up removing the top and changing it out to match the tab-locking bottom piece, while retaining the slot-locking sides and front piece, which allowed her to shrink the front piece down and make the area surrounding the LCD symmetric. The final case retains a lot of the details I enjoyed making while matching Adafruit's own preferences. The following pictures show what the final production design will look like.

Fig 5. Back in Black

Fig 6. Symmetric Side Profile

Fig 7. Rear View

Wednesday, February 3, 2010

Rapid Prototyping

There's a lot of ground that's covered by the umbrella term of 'rapid prototyping,' but one aspect that's conceptually straightforward is usually a pain to tackle. Having a solution in-hand, I'm excited to share it.

Q. How do I convert from my CAD format to a DXF so that I can cut out my circuit on a laser cutter or cutting plotter?

Why would you ever want to do this? Well, perhapse you sent out some PCB files to be manufactured and wanted to cut your own mylar solder-paste stencils on a laser cutter. Possibly you're making your own flex-circuits at home out of aluminum foil and contact paper (if you don't have a cutting plotter you could always use an iron-on transfer, an X-acto knife, an inkjet printer and some really steady hands). Maybe you wanted to clone all of your drill hole placement and so that you could make a jig to use with your drill press. Some artist came by your lab and thought that your high-speed impedance-matched data bus would look super futuristic if it were water-jet cut out of sheet titanium and sold to fashionistas as jewelry. Or you think the Arduino layout would make a really awesome graffiti stencil (if only you could loss-lessly scale it up 50x and cut it out of plastic). Lots of applications require getting your CAD layout into some non-CAD format, and preferably a vector format. So, now that you have the 'why', here's the 'how'.

A. You'll need your CAD software, a decent print manager and Adobe Illustrator or equivalent software.
  1. Starting with your layout - select-to-display only those features of the layout that you want to "print". Then print your file (non-scaled) to PostScript (.ps).
  2. Open your PostScript (.ps) file with Adobe Illustrator. At this point, all of your 'traces' will be 'lines', aka 'strokes' with a defined width, which you don't want. You want an actual closed 'outline'/path that describes where the laser/knife should be applied by your relevant plotter.
  3. Delete any features (like origin markings) that you don't want and Object -> Group the ones that remain.
  4. Then copy what's left into a new layer (for safety). AKA: Select -> All; Edit -> Copy; Window -> Layers -> New Layer; Edit -> Paste
  5. Make the original layer invisible, so as not to muck with it.
  6. Select -> All ; Object -> Path -> Outline Stroke
  7. Object -> Expand
  8. Window -> Pathfinder
  9. And then in the Pathfinder window (have everything selected), click on 'Unite' and then Option-click on your selected object.
  10. Export your file to DXF using File -> Export.
  11. BAM!