Hackaday Links: July 13, 2014


Don’t like sunglasses? Deal with it. They’re the pixeley, retro sunglasses from your favorite animated .GIFs, made real in laser cut acrylic. Points of interest include heat-bent frames made out of a single piece of acrylic.

Remember this really small FPGA board? The kickstarter is ending really soon and they’re upgrading it (for an additional $30) with a much better FPGA.

Sparkfun is now hosting the Internet of Things. They’re giving people a tiny bit of space to push data to, and you can also deploy your own server. That’s interesting, and you can expect us doing a full post on this soon.

Need waveforms? [Datanoise] is building a wavetable synthesizer, and he’s put all his waveforms online. Now if we could just get a look at the synth…

If you only have $20 to spend on a board, you’ll want to pick up at Teensy 3.1. [Karl] wrote some bare metal libraries for this awesome board, and while it’s not as extensive as the standard Arduino libs, it’s more than enough to get most projects off the ground. Included are UARTs, string manipulation tools, support for the periodic interval timers on the chip, and FAT and SD card support.

Koch Lamp is 3D Printed with a Twist

Koch Lamp

[repkid] didn’t set out to build a lamp, but that’s what he ended up with, and what a lamp he built. If the above-pictured shapes look familiar, it’s because you can’t visit Thingiverse without tripping over one of several designs, all based on a fractal better known as the Koch snowflake. Typically, however, these models are intended as vases, but [repkid] saw an opportunity to bring a couple of them together as a housing for his lighting fixture.

Tinkering with an old IKEA dioder wasn’t enough of a challenge, so [repkid] fired up his 3D printer and churned out three smaller Koch vases to serve as “bulbs” for the lamp. Inside, he affixed each LED strip to a laser-cut acrylic housing with clear tape. The three bulbs attach around a wooden base, which also holds a larger, central Koch print at its center. The base also contains a PICAXE 14M2 controller to run the dioder while collecting input from an attached wireless receiver. The final component is a custom control box—comprised of both 3D-printed and laser-cut parts—to provide a 3-dial remote. A simple spin communicates the red, green, and blue values through another PICAXE controller to the transmitter. Swing by his site for a detailed build log and an assortment of progress pictures.


A Transparent 7-Segment Display

Though [Connor] labels it as a work in progress, we’re pretty impressed with how polished his transparent 7-segment display looks. It’s also deceptively simple.

The build uses a stack of seven different acrylic panes, one in front of the other, each with a different segment engraved onto its face. The assembly of panes sits on a small mount which is placed over seven rows of LEDs, with 5 LEDs per row. [Connor] left an air gap between each of the seven individual acrylic panes to clearly distinguish which was lit and to match the separation of the LED rows. To display a number, he simply illuminates the appropriate LED rows, which scatter light across the engraved part without spilling over into another pane.

You can find a brief overview and some schematics on [Connor’s] website, and stick around for the video demonstration below. We’ve featured [Connor’s] work before; if you missed his LCD data transfer hack you should check it out!

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Homemade Polariscope is Super Easy to Make


[Abhimanyu Kumar] was watching YouTube videos one day when he came across something called a Polariscope — After learning how it worked, he discovered you can make your own using household items!

First off, what is a Polariscope? Well, put simply, it is a device that can show you the photoelasticity of a clear specimen, which can reveal the stress distribution in the material! And it is actually really easy to make one.

All you need to build your own is:

  • A polarized light source (any modern LCD monitor)
  • A transparent specimen (plastic cutlery, glass statues, plastic you can bend, etc)
  • A circular polarizing filter (the cheap 3D glasses you didn’t return at the theater)

Then just place the objects in the order shown in the diagram and start snapping some photos. This would be really cool for checking stress concentrations in a project — provided you are using some Lexan or acrylic!

Snowden Immortalized as Bond Villain in Edge-Lit Acrylic Poster


[Wilywyrm] needed to come up with a final project for art class that commented on a social issue. Healthcare, schmealthcare, he said, and busted out this movie poster about the NSA spying scandal instead.

The circuit uses three extended-duty astable 555 timers to control the brightness of the 5050 RGB common-anode LED strips that run up the sides of the 24″ x 12″ x 1/4″ acrylic panels. Each of the three panels was laser-engraved at 600 DPI on an Epilog laser engraver and features a different aspect of the poster. There’s one for Snowden, one for Daniel Craig, and one for the text.

[Wilywyrm] tied the color channels together in the first panel to output white light. He used red for the second panel and blue for the third. A complete list of parts with build notes is available on his Google Drive. [Wilywyrm]’s notes include improvement ideas, like making all the RGB strips color-adjustable with more 555s or a microcontroller and timers.

Perhaps [Wilywyrm] could get into the clear whiteboard business after college.

Laser cut Arc Reactor replica


We’re starting to become a repository for Arc Reactor replica projects. The one shown above uses mostly laser cut components. We missed it back in May when [Valentin Ameres] tipped us off the first time. But he sent it in again after seeing the 3D printed version earlier this month.

Our biggest gripe is that we don’t have our own laser cutter to try this out on. Everything has been cut from 2mm thick acrylic. The black, silver, and copper colored components were painted to achieve this look. Many of the clear parts also had a dot matrix etched into them to help with light diffusion.

Basic assembly just required the parts be glued together. The finishing touches include wire-wrapping the slots of the outer ring and adding LEDs and current limiting resistors.

The plans are not freely available, but the 3D printed version linked above doubles as a 123D tutorial. That should help get you up to speed designing your own if you are lucky enough to have time on laser cutter.

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Polishing optics milled from acrylic


[Ben Krasnow] milled some lenses out of cast acrylic and needed a way to get an optical finish on the tool-marked surface. He tested several acrylic finishing methods to achieve a crystal clear finish. The tests were done using flat chunks. A regiment of sandpaper, from coarse to fine, was used as the first stage of the operation. From there [Ben] sought out the best finishing step, starting with hand polishing tests, flame polishing, and methylene chloride vapor polishing (which is something along the lines of acetone vapor polishing for 3D printed ABS parts).

Flame polishing and vapor polishing are not really exact sciences… at least in the tests he performed. It was difficult to know exactly how long to expose the acrylic. Too short or too long resulted in poor clarity. Watch his video to get a look at all results. We’d say the the easiest way to make milled acrylic clear without achieving an optical finish is to flame polish it as it doesn’t really require that you sand it ahead of time. But [Ben’s] tests prove that you can’t beat hand polishing with 600 then 2000 grit sandpaper before finishing up with a liquid plastic polish.

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