Two-Stage Tentacle Mechanisms Part III: Putting It All Together

October 21, 2016 by Sonya Vasquez 31 Comments

Welcome back to the final chapter in our journey exploring two-stage tentacle mechanisms. This is where we arm you with the tools and techniques to get one of these cretins alive-and-kicking in your livingroom. In this last installment, I’ll guide us through the steps of building our very own tentacle and controller identical to one we’ve been discussing in the last few weeks. As promised, this post comes with a few bonuses:

29323707092_28d8bd1eb8_z — Nothing like a fresh batch o’ parts.

Design Files

The Almighty Bill-o’-Materials
Vector Drawings for laser cutting
1. DXF files pre-offset (0.003″)
2. DXF files original
STL Models for 3D Printing
Original Tentacle CAD Model Files
Original Controller CAD Model Files

Depending on your situation, some design files may be more important than others. If you just want to get parts made, odds are good that you can simply cut the pre-offset DXFs from the right plate thicknesses and get rolling. Of course, if you need to tune the files for a laser with a slightly different beam diameter, I’ve included the original DXFs for good measure. For the heavy-hitters, I’ve also included the original files if there’s something about this design that just deserves a tweak or two. Have at it! (And, of course, let us know how you improve it!)

Ok, now that we’ve got the parts on-hand in a pile of pieces,let’s walk through the last-mile tweaks to making this puppet work: assembly and tuning. At this point, we’ve got a collection of parts, some laser-cut, some off the shelf. Now it’s time to string them together.

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Down The Rabbit Hole And Back Out Again: Serial Over Headphone Jack

October 21, 2016 by Elliot Williams 14 Comments

[ttsiodras] tells an epic tale of getting a custom Debian kernel installed on an Asus MemoPAD (ME103K) tablet. Skipping to the end of the saga, he discovers what looks like serial data coming out on the headphone jack when the system boots, but the signal was so distorted that he couldn’t simply interpret it. The solution turns out to be attaching a level-converter chip.

A level converter is a non-inverting amplifier, usually with a Schmitt trigger for immunity against noise. In this case, it acts like a “binarizer” — outputting a high voltage when the input rises above a threshold, and a low when it drops below. It’s the right part when you need to clean up a messy digital signal, and in this case works just fine because the capacitive distortion effects slow down both the leading and trailing edges of the signal, keeping the serial data’s timing intact.

That was the spoiler. If you want to read up on putting a custom Linux on an Android device, check out [ttsiodras]’s first post where he backs the machine up, and the second where he gets his custom kernel up and running. If you’re ever faced with an Android tablet that hasn’t been owned yet, or if you just have a DIY streak, this should help you get started.

Using the audio jack for serial is actually not uncommon, and discovering a serial terminal that listens at boot time is our favorite way to wedge a Linux OS into odd devices. So when you see a funny, distorted signal coming out at 115,200 baud, take a moment to clean its edges up and see what you’ve got.

A Machine Shop In A Toolbox: Just Add Time

October 21, 2016 by Gerrit Coetzee 73 Comments

You don’t need any fancy tools. A CNC machine is nice. A 3D printer can help. Laser cutters are just great. However, when it comes to actually making something, none of this is exactly necessary. With a basic set of hand tools and a few simple power tools, most of which can be picked up for a pittance, many things of surprising complexity, precision, and quality can be made.

Not as pretty, but worked just the same.

A while back I was working on a ring light for my 3D printer. I already had a collection of LEDs, as all hackers are weak for a five-dollar assortment box. So I got on my CAD software of choice and modeled out a ring that I was going to laser cut out of plywood. It would have holes for each of the LEDs. To get a file ready for laser cutting ook around ten minutes. I started to get ready to leave the house and do the ten minute drive to the hackerspace, the ten minutes firing up and using the laser cutter (assuming it wasn’t occupied) and the drive back. It suddenly occurred to me that I was being very silly. I pulled out a sheet of plywood. Drew three circles on it with a compass and subdivided the circle. Under ten minutes of work with basic layout tools, a power drill, and a coping saw and I had the part. This was versus the 40 minutes it would have taken me to fire up the laser cutter.

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Send A Raspberry Pi Back In Time To 1980

October 21, 2016 by Elliot Williams 28 Comments

One of our favorite hacker-scavengers on YouTube, [The Post-Apocalyptic Inventor], has been connecting his Raspberry Pi up to nearly every display that he’s got in his well-stocked junk pile. (Video embedded below.)

Modern monitors with an HDMI input connect right up to the Pi. Before HDMI came VGA, but the Pi doesn’t do that natively. One solution is to use a composite-to-VGA converter and pull the composite signal out of the audio jack. Lacking the right 4-pole audio cable, [TPAI] soldered some RCA plugs directly onto the Pi, and plugged that into the converter. On a yet-older monitor, he faced a SCART adapter. If you’re European, you’ll know these — it’s just composite video with a different connector. Good thing he had a composite video signal already on hand.

The pièce de resistance, though, was attaching the Pi to his 1980 Vega TV set. It only had an antenna-in connector, so he needed an RF modulator. With a (presumably) infinite supply of junk VCRs on hand, he pulled an upconverter out of the pile, and got the Pi working with the snazzy retro TV.

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3D Print An Enigma Machine That’s Close To The Real Thing

October 21, 2016 by Jenny List 6 Comments

The Enigma machine as used by the German military during World War Two exerts a curious fascination among our community of hardware hackers and makers. Perhaps it is the mechanical complexity of the machine itself, or maybe the tale of how its encoded messages were decrypted by Allied codebreakers that contributes to this interest, but whatever it is we’ve seen a succession of Enigma-related projects over the years that shows no sign of abating.

The latest Enigma project to come our way is a particularly nice one from a group of first year students at CentraleSupélec Rennes, in Northwestern France. Their Réplique Enigma is a fully mechanical Enigma replica using 3D printing techniques, and unlike so many replicas which use modern electronics it has a set of rotors just like those you would have found in the original. The rotors themselves have a 3D-printed plastic shell which houses brass contacts and the associated writing, while the keyboard and lamp board are both made from plywood. Rather than trying to replicate the original switches from the keyboard they are using modern microswitches, however the keys themselves are upright posts that resemble the original. An AZERTY layout may not have been present on the real Enigma machines, but lends a pleasing twist to the build.

It’s worth browsing all the pages for this build, as the front page does not necessarily capture the whole build. The rotors set this Enigma apart from many of the replicas we’ve featured in the past, so you may find it interesting to take a look and make a few comparisons.

Hackaday Prize Entry: Antigravity Arm Floaties

October 20, 2016 by Brian Benchoff 19 Comments

A few years ago, [Mike] heard about orthotic devices for people in wheelchairs that make it easier to them to move their arms. His daughter had the opportunity to demo one of these devices, and the results with the device were good. The fights with the insurance company were not so good, but this really was a device that could be made on a 3D printer with a few rubber bands, after all. Thus, [Mike] invented 3D printed antigravity arm floaties.

The name basically tells the story — these antigravity arm floaties work well to counter the pull of gravity for individuals with low muscle tone. [Mike]’s daughter found the professional, official, not-covered-by-insurance version useful, so [Mike] decided to build his own. There’s really not much to it – it’s just a few 3D printed parts attached to a wheelchair with a few rubber bands giving the mechanical linkages some resistance.

In the true hacker spirit, [Mike] took the basic idea of these spring-loaded arm floaties and put a new twist on it. He’s using a chain as the mechanism that allows freedom of movement in the XY plane. This makes the device slightly better, and is by every account an improvement on the commercial version. That’s what you get when you can iterate quickly with a 3D printer, making this project an excellent example of what we’re looking for in the Assistive Technology portion of the Hackaday Prize.

A Slice Of Ubuntu

October 20, 2016 by Al Williams 24 Comments

The de facto standard for Raspberry Pi operating systems is Raspbian–a Debian based distribution specifically for the diminutive computer. Of course, you have multiple choices and there might not be one best choice for every situation. It did catch our eye, however, that the RaspEX project released a workable Ubunutu 16.10 release for the Raspberry Pi 2 and 3.

RaspEX is a full Linux Desktop system with LXDE (a lightweight desktop environment) and many other useful programs. Firefox, Samba, and VNC4Server are present. You can use the Ubuntu repositories to install anything else you want. The system uses kernel 4.4.21. You can see a review of a much older version of RaspEX in the video below.

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