Relay Computing

January 19, 2017 by 25 Comments

Recently, [Manuel] did a post on making logic gates out of anything. He mentioned a site about relay logic. While it is true that you can build logic gates using switch logic (that is, two switches in series are an AND gate and two in parallel are an OR gate), it isn’t the only way. If you are wiring a large circuit, there’s some benefit to having regular modules. A lot of computers based on discrete switching elements worked this way: you had a PCB that contained some number of a basic gate (say, a two input NAND gate) and then the logic was all in how you wired them together. And in this context, the SPDT relay was used as a two input multiplexer (or mux).

In case you think the relay should be relegated to the historical curiosity bin, you should know there are still applications where they are the best tool for the job. If you’re not convinced by normal macroscopic relays, there is some work going on to make microscopic relays in ICs. And even if they don’t use relays to do it, some FPGAs use mux-based logic inside.  So it’s worth your time to dig into the past and see how simply switching between two connections can make a computer.

Mux Mania

How do you go from a two input mux to an arbitrary logic gate? Simple, if you paid attention to the banner image. (Or try it interactive). The mux symbols show the inputs to the left, the output to the right and the select input at the bottom. If the select is zero, the “0” input becomes the output. If the select is one, the “1” input routes to the output.

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3D Printer With Tilted Bed

January 19, 2017 by 37 Comments

[Oliver Tolar] and [Denis Herrmann], two students from the Zurich University of Applied Sciences (ZHAW), designed and produced a 3D printer prototype that has a movable printing bed that can tilt. By tilting, objects with critical overhangs can be printed without the additional support material. The printer has six axes, three axes control the print head as usual and three other axes control the printing bed, allowing a wider range of movements.

The students claim that besides saving on the support material this printer can actually save time while printing objects that need a lot of support since, we assume, it’s faster to tilt the bed than to print the support itself. In normal 3D printers the plate is always horizontal and the print object is built up in horizontal layers. In this printer, for large overhangs, the printing bed is held in such a way that the print object is pivoted until perpendicular to the print head. Of course, for round shapes it will probably be different but we only saw it in action in one demonstration video. There is also the plus side that, when a print finishes, it’s finished. No x-acto knife to remove support, no sand paper, no time wasted.

Having the software controlling the bed properly was more difficult than the assembly of the printer, they said. It is still under development as it cannot, for example, simultaneously move the print head and printing bed to produce a continuous print.

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Will Supercapacitors Ever Replace Batteries?

January 19, 2017 by 124 Comments

Recharging your mobile phone or your electric vehicle in a few minutes sure sounds appealing. Supercapacitor technology has the potential to deliver that kind of performance that batteries currently can’t, and while batteries are constantly improving, the pace of development is not very fast. Just remember your old Nokia mobile with Ni-Cad batteries and several days of usage before a recharge was needed. Today we have Lithium-Ion batteries and we have to charge our phones every single day. A better energy storage option is clearly needed, and supercapacitors seem to be the only technology that is close to replace the battery.

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[Marla]’s New Arm

January 19, 2017 by 32 Comments

It is especially rare to see coverage in the mainstream media that involves a hackspace, so it was a pleasant surprise yesterday when the local TV news where this is being written covered a story that not only highlighted a hackspace’s work, but did so in a very positive light.

[Marla Trigwell] is a young girl from Newbury, UK, who was born without a left hand. She had been provided with prosthetics, but they aren’t cheap, and as a growing child she quickly left them behind. Her parents researched the problem as modern parents do, and found out about recent advances in 3D-printed prosthetics lowering the bar to access for those like [Marla] born without a limb. Last month [Marla] received her new 3D-printed arm, and she did so courtesy of the work of [Andrew Lindsay] at Newbury and District Hackspace.

The arm itself is a Team Unlimbited arm version 2.0 Alfie edition, which can be found on Thingiverse with full sizing instructions for adjusting to the recipient in Customizer. As the video below the break shows, [Marla] appears very pleased with it, and is soon mastering its ability to grip objects.

This story is a fantastic demonstration of the ability of a hackspace to be a force for good, a true community organisation. We applaud [Andrew], NADHack, and all involved with it for their work, and hope that 3D printed arms will keep [Marla] with a constant supply of comfortable and affordable prosthetics as she grows up.

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Print Flexible PCBs With A 3D Printer

January 19, 2017 by 21 Comments

Let’s get it out of the way right up front: you still need to etch the boards. However, [Mikey77] found that flexible plastic (Ninjaflex) will adhere to a bare copper board if the initial layer height is set just right. By printing on a thin piece of copper or conductive fabric, a resist layer forms. After that, it is just simple etching to create a PCB. [Mikey77] used ferric chloride, but other etchants ought to work, as well.

Sound simple, but as usual, the devil is in the details. [Mikey77] found that for some reason white Ninjaflex stuck best. The PCB has to be stuck totally flat to the bed, and he uses spray adhesive to do that. Just printing with flexible filament can be a challenge. You need a totally constrained filament path, for one thing.

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Use A Brushless Motor As A Rotary Encoder

January 18, 2017 by 17 Comments

The electric motor is the fundamental building block of almost all robotic projects but, without some form of feedback, it lacks the precise positional control required for the task. Small servos from the modelling world will often use a potentiometer to sense where they are on their travel, while more accomplished motors will employ some form of shaft encoder.

Commercial shaft encoders use magnets and Hall-effect sensors, or optical sensors and encoder discs. But these can be quite expensive, so [Hello1024] hacked together an alternative in an afternoon. It uses another motor as the encoder, taking advantage of the minute changes in inductance as the magnet passes each of its coils. It’s a technique that works better with cheaper motors, as their magnets are more imperfect than those on their expensive cousins.

The sensing is rather clever in its economy, sending a pulse to the motor through an off the shelf motor controller and measuring the time it takes to decay through the body diode of the driving MOSFET. It requires a calibration procedure before first use, and it is stressed that the whole thing is very much still in beta, but it’s a very impressive hack nevertheless. He’s posted a video demonstration which you can see below the break.

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Programming Thousands Of AVRs

January 18, 2017 by 24 Comments

It is funny how almost everything has its own set of problems. Rich people complain about taxes. Famous people complain about their lack of privacy. It probably won’t happen us, but some Kickstarter campaigners find they are too successful and have to scale up production, fast. We’d love to have any of those problems.

[Limpkin] found himself in just that situation. He had to program several thousand Atmel chips. It is true that you can get them programmed by major distributors, but in this case, he wanted unique serial numbers, cryptographic keys, and other per-chip data programmed in. So he decided to build his own mass programming workbench.

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