Visual cryptography is one of those unusual cases that kind of looks like a good idea, but it turns out is fraught with problems. The idea is straightforward enough — an image to encrypt is sampled and a series of sub-pixel patterns are produced which are distributed to multiple separate images. When individual images are printed to transparent film, and all films in the set are brought into alignment, an image appears out of the randomness. Without at least a minimum number of such images, the original image cannot be resolved. Well, sort of. [anfractuosity] wanted to play with the concept of visual cryptography in a slightly different medium, that of a set of metal plates, shaped as a set of keyrings.
Metal blanks were laser cut, with the image being formed by transmitted light through coincident holes in both plate pairs, when correctly aligned. What, we hear you ask, is the problem with this cryptography technique? Well, one issue is that of faking messages. It is possible for a malicious third party, given either one of the keys in a pair, to construct a matching key composing an entirely different message, and then substitute this for the second key, duping both original parties. Obviously this would need both parties to be physically compromised, but neither would necessarily notice the substitution, if neither party knew the originally encrypted message. For those interested in digging in a little deeper, do checkout this classic paper by Naor and Shamir [pdf] of the Wiezmann Institute. Still, despite the issues, for a visual hack it’s still a pretty fun technique!
The finished lamp shade is spherical, but is made entirely from flat-packed pieces of laser-cut wood that have been specifically designed to minimize distortion when assembled into a curved shape. The pieces themselves are reminiscent of puzzle cells; complex, interlocking cellular shapes found in many plants.
As usual, [Nervous System] applied a hefty dose of math and computational design to arrive at a solution. Each unique panel of the lamp is the result of a process that in part implements a technique called variation surface cutting for the shape of the pieces. They also provide a couple of nifty animations that illustrate generating both the piece boundaries as well as the hole patterns in each of the 18 unique pieces that make up each lamp.
As for making the pieces themselves, they are laser-cut from wood veneer, and assembly by the end user takes an hour or two. Watch a video overview, embedded just below under the page break.
We’re glad [Nervous System] takes the time to share details like this, just like the time they figured out the very best type of wood for laser-cutting their unique puzzles and didn’t keep it to themselves.
Who are you? No, who are you really? You’re an amalgamation of influences from your family, your friends, the media, and the parasocial relationships you have with fictional characters. It’s okay; we all are. It can’t be helped that there’s a lot of it about.
In this case, the light comes from a hacked camping headlamp that was past its prime. [Kim] laser-cut the letters from acrylic and submerged them in water, which can be manipulated to enhance the effect and mimic the turmoil of life. For added effect, [Kim] held prisms in the light’s path to refract it and cause the patterns to dance. Be sure to check it out after the break, and don’t forget to turn on the sound so you can hear [Kim]’s original composition.
Inside a modern laptop there is surprisingly little in the way of parts, now that removable media drives are largely a thing of the past and once the battery has been removed from the equation. When the keyboard and trackpad are subtracted and replaced with USB equivalents the inner workings are reduced to a relatively compact motherboard and hard drive alongside the screen.
The screen is encased in a lasercut frame that also mounts the motherboard. It includes a lasercut cover that folds over the top in a living hinge to create an A-frame case that also holds the power supply. As an extra bonus the centre of the A provides handy storage for a keyboard.
[Jesse]’s modification doesn’t affect the laser beam itself; it is an improvement on the air assist, which is the name for a constant stream of air that blows away smoke and debris as the laser burns and vaporizes material. An efficient air assist is one of the keys to getting nice clean laser cuts, but [Jesse] points out that a good quality air assist isn’t just about how hard the air blows, it’s also about how smoothly it does so. A turbulent air assist can make scorch marks worse, not better.
As an experiment to improve the quality of the air flowing out the laser nozzle, [Jesse] researched ways to avoid turbulence by creating laminar flow. Laminar flow is the quality of a liquid having layers flowing past one another with little or no mixing. One way to do this is to force liquid through individual, parallel channels as it progresses towards a sharply-defined exit nozzle. While [Jesse] found no reference designs of laminar flow nozzles for air assists, there were definitely resources on making laminar flow nozzles for water. It turns out that interest in such a nozzle exists mainly as a means of modifying Lonnie Johnson’s brilliant invention, the Super Soaker.
Working from such a design, [Jesse] created a custom nozzle to help promote laminar flow. Sadly, a laser cutter head carries design constraints that make some compromises unavoidable; one is limited space, and another is the need to keep the laser’s path unobstructed. Still, after 3D printing it in rigid heat-resistant resin, [Jesse] found a dramatic improvement in the feel of the air exiting the nozzle. Some test cuts confirmed a difference in performance, which results in a noticeably cleaner kerf without scorching around the edges.
One of the things [Nervous System] does is make their own custom puzzles, so any improvement to laser cutting helps reliability and quality. When production is involved, just about everything matters; a lesson [Nervous System] shared when they discussed making the best plywood for creating their puzzles.
Test and programming fixtures are great time-savers for anyone who needs to deal with more than a handful of PCBs. Instead of plugging in connectors (or awkwardly holding probe tips or wires) to program some firmware or run tests, one simply pops a PCB into a custom fixture with one hand, and sips a margarita with the other while a program decides whether everything is as it should be. Test fixtures tend to be custom-made for specific board layouts, meaning one tester is needed per board or device type, but this work is easily justified by the huge time savings they offer.
The test unit looks like pretty familiar stuff at first glance: some hardware responsible for running the test program, laser-cut acrylic jig to hold a test PCB in a consistent position, spring-loaded pogo pins to make temporary electrical connections, and LEDs to clearly indicate PASS and FAIL states. The clever part is the way the fixture is designed to accommodate multiple board designs, and how it uses several 74LVC4066 quad bilateral switch ICs to take care of switching which pogo pins are connected and to where.
As mentioned, to be compatible with multiple boards there must be common design elements to exploit. In Sparkfun’s case, the through-hole connections on their breakout boards are all in a row with standard 0.1″ spacing. By using the aforementioned pogo pins and 4066 ICs, different pinouts can be accommodated and multiple board types can be used without any need to swap to different test hardware.
We hadn’t considered how challenging it might be to try drawing long-term on a tablet, and it sounds as though Apple didn’t, either. According to [Eric Strebel], who normally designs products for other people, there are many problems to solve. The camera area creates a bump on an otherwise flat backside, so it wobbles on the table. It’s thick. It’s too easy to run your stylus off the side.
Yes there are tablet holders out there, even a few with cup holders, but almost none of them have a kickstand for holding the thing vertically. If you want something done right, you have to do it yourself. And so [Eric] designed his ideal stand to solve all of these problems (video, embedded below). It’s mostly made of laser-cut foam core board, with some layers of poster board added to make the bezel totally flush with the tablet.
[Eric] can snap the tablet in place and use it flat, or fold back the upper half into a stand. It even works well over on the couch, or sitting up in bed. We particularly like the window gasket feet and all the versions of his hinges, which start with strips of cheesecloth and end in grosgrain ribbon. [Eric]’s approach to design always reminds us to keep an open mind about materials and methods. If you try using what you already have, the results may surprise you. Check out the build video after the break.