### Magnets and Geometry

A bunch of us are in the middle of a short fad of fascination with magnets. I recently purchased about a thousand gold-plated spherical 6mm N35 neodymium-iron-boron magnets from Edwin Science. These are strong enough that swallowing two of them would probably require surgery. But I am not dumb enough to eat them, being far more interested in building things out of them, and thus I give you some photos of the nifty things I did when I got them, and some tips on how to assemble them. I regret not having the artistic skills or patience to illustrate all of the information I want to share here, but hopefully those interested can follow along.

The first building block is a loop of magnets, with the poles aligned circumferentially (that is, a string of aligned magnets joined end to end). In the photos below, anywhere you see two parallel rows of magnets arranged in a square configuration, that indicates the adjacent rows are aligned in opposite directions, and almost always part of separate loops. If the rows are arranged in a triangular configuration, that indicates they are aligned in the same direction. The loops can be treated as polygons (squares, pentagons, hexagons, octagons, etc) to create polyhedra. The strength of the magnets causes them to exert force in the direction of perfect alignment, which gives rigidity to what would otherwise be flexible circles.

Two or more loops of the appropriate relative size can be stacked to form a shape somewhere between a cone and a pyramid. 5-10-15-20 makes a pentagonal pyramid, 4-8-12-16 makes a square pyramid, 6-9-12-15 (a "loop" of 3 magnets is not stable) makes a triangular pyramid. For reasons related to the bulk of the individual spheres, the triangular pyramid is too tall and too circular to be of much use, which is unfortunate since a triangle is by far the most useful shape for building polyhedra. The square pyramid is better, but far less useful. This leaves the pentagonal pyramid as the building block of choice for a large number of assemblies. Each "pyramid" can be assembled from as few as two to as many as four concentric rings (a fifth ring results in most structures being too heavy to support their own weight... until I get some N52 spheres!). Each layer can be "up" or "down", so you may get a rippled surface instead of a cone shape, and the entire resulting shape can be installed into the final product pointing out or in. Also of note is that the pyramids have a "handedness". Where the rings can be simply flipped over if they are out of alignment, the pyramids have to be inverted if you need to flip them.

1. How much did a thousand of those cost?

2. About \$105 for 1100 magnets. I haven't seen cheaper.

3. Complex shapes made from magnetic spheres:

### Building an enclosure for the LulzBot AO 100

As the cold weather season arrives in Atlanta, with it comes issues with our 3D printers. Specifically problems with temperatures and print stability. Freeside is essentially a big warehouse, and our 3D printing station is setup in the large open area in the front of the space. What this means is that when it is cold in the space, this will affect the printing quality because the ambient temperature is far lower than what is optimal for thermoplastics. The cold ambient air will cause parts to rapidly cool during the middle of a print. And with materials like ABS which can shrink dramatically during cooling, this causes prints to warp, deform, and delaminate during and after printing is finished. The print on the left is showing signs of delamination from plastic cooling mid print. To remedy this, we built an acrylic enclosure for our LulzBot AO-100, which is our dedicated ABS printer. We tested the proof of concept of whether an enclosure would help mitigate printing problem

### Build-Out Recap!

A bunch of great stuff got done at the build-out yesterday. A huge thanks to everyone that came out to pitch in! Here are some pictures to recap the projects... Randy's team hung the curtain to the workshop to create more of a barrier between the front of the house and back of the house and to control dust levels a bit more. We'll be finishing the top of the wall soon, but the hard part's already done. Karen, Donald, Tom, Violet, and James framed the doorway to the Media Lab and Bio Lab and hung the door for that area. Next step is AC! Michelle and Mary's team cleaned out project storage and moved the shelves over so that Neils could put the flammability cabinets in that area. That allowed all of us with the help of Adam and Nathan to clean up the workshop and really tidy up. They also sorted out all of the laser cutter raw materials and cut them down to a usable size on the table saw.  For the portal clouds, JW, Nathan, and Kat rolled an aw

### A Capacitive-Touch Janko Keyboard: What I Did at the 2017 Georgia Tech Moog Hackathon

Last weekend (February 10-12, 2017) I made a Janko-layout capacitive-touch keyboard for the Moog Werkstatt at the Georgia Tech Moog Hackathon. The day after (Monday the 13th), I made this short video of the keyboard being played: "Capacitive Touch Janko Keyboard for Moog Werkstatt" (Text from the video doobly doo) This is a Janko-layout touch keyboard I made at the 2017 Moog Hackathon at Georgia Tech, February 10-12. I'm playing a few classic bass and melody lines from popular and classic tunes. I only have one octave (13 notes) connected so far. The capacitive touch sensors use MPR121 capacitive-touch chips, on breakout boards from Adafruit (Moog Hackathon sponsor Sparkfun makes a similar board for the same chip). The example code from Adafruit was modified to read four boards (using the Adafruit library and making four sensor objects and initializing each to one of the four I2C addresses is remarkably easy for anyone with moderate familiarity with C++), and