Day: October 23, 2017

MakerBot Really Wants You To Like Them Again

October 23, 2017 by 76 Comments

For the last couple years, a MakerBot press release has generally signaled that more pink slips were going to be heading out to the already shell-shocked employees at their NYC factory. But just last week something that could almost pass as good news came out of the once mighty 3D printer manufacturer, the unveiling of “MakerBot Labs”. A number of mainstream tech sites heralded this as MakerBot’s first steps back into the open source community that launched it nearly a decade ago; signs of a newer and more thoughtful MakerBot.

Reading the announcement for “MakerBot Labs”, you can almost believe it. All the buzz words are there, at least. In fact, if this announcement came from anyone else, in any other field, I’d probably be on board. Sharing knowledge and listening to the community is essential if you want to connect with hackers and makers. But this is MakerBot, and they’ve dug themselves into a very deep hole over the years.

The spectacular fall from grace that MakerBot has experienced, from industry leader to afterthought, makes this hat-in-hand peace offering hard to take seriously. It reads like a company making a last ditch effort to win back the users they were so sure they didn’t need just a few years ago. There is now a whole new generation of 3D printer owners who likely have never even seen a MakerBot printer, and it’s hard to imagine there’s still enough innovation and life in the company to turn that around before they completely fade into obscurity.

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The Grafofon: An Optomechanical Sequencer

October 23, 2017 by 4 Comments
There are quick hacks, there are weekend projects and then there are years long journeys towards completion.  [Boris Vitazek]’s grafofon falls into the latter category. His creation can best be described as electromechanical sequencer synthesizer with a multiplayer mode.
The storage medium and interface for this sequencer is a thirteen-meter loop of paper that is mounted like a conveyor belt. Music is composed by drawing on the paper or placing objects on it. This is usually done by the audience and the fact that the marker isn’t erased make the result collaborative and incremental.
 These ‘scores’ are read by a camera and interpreted by software.This is a very vague description of this device, for a reason: the build went on over six years and both hard- and software went through several revisions in that time. It started as a trigger for MIDI notes and evolved from there.
In his write up [Boris] explains the technical aspects of each iteration. He also tells the stories of the people he met while working on the grafofon and how they influenced the build. If this look into the art world reminds you of your local hackerspace, it is because these worlds aren’t that far apart.

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Lithium Ion Versus LiPoly In An Aeronautical Context

October 23, 2017 by 32 Comments

When it comes to lithium batteries, you basically have two types. LiPoly batteries usually come in pouches wrapped in heat shrink, whereas lithium ion cells are best represented by the ubiquitous cylindrical 18650 cells. Are there exceptions? Yes. Is that nomenclature technically correct? No, LiPoly cells are technically, ‘lithium ion polymer cells’, but we’ll just ignore the ‘ion’ in that name for now.

Lithium ion cells are found in millions of ground-based modes of transportation, and LiPoly cells are the standard for drones and RC aircraft. [Tom Stanton] wondered why that was, so he decided to test the energy density per mass of these battery chemistries, and what he found was very interesting.

The goal of [Tom]’s experiment was to test LiPoly against lithium ion batteries in the context of a remote-controlled aircraft. Since weight is what determines flight time, cutting even a few grams from an airframe can vastly extend the capabilities of an aircraft. The test articles for this experiment come in the form of a standard 1800 mAh LiPoly battery and four 18650 cells wired together as a 3000 mAh battery. Here’s where things get interesting: the LiPoly battery weighs 216 grams for an energy density of 0.14 Watt-hours per gram. The lithium ion battery weighs 202 grams for an energy density of 0.25 Watt-hours per gram. If you just look at the math, all drones are doing it wrong. 18650 cells appear to have a much higher energy density per mass than the usual LiPoly cells. How does that hold up in a real-world test, though?

Using his neat plane with 3D printed wing ribs as the testbed, [Tom] plugged in the batteries and flew around a field for the better part of an afternoon. The LiPo flew for 41.5 minutes, whereas the much more energy dense lithium ion battery flew for 36.5 minutes. What’s going on here?

While the lithium ion battery has a much higher capacity, the problem here is the internal resistance of each battery chemistry. The end voltage for the LiPo was a bit lower than the lithium ion battery, suggesting the 18650 cells can be run down a bit further than [Tom]’s test protocol allowed. After recharging each of these batteries and doing a bit of math, [Tom] found the lithium ion batteries can fly for about twice as long as their LiPo counterparts. That means an incredibly long test of flying a plane in a circle over a field; not fun, but we are looking forward to other people replicating this experiment.

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