Measuring The Stiffness Of 3D-Printed Parts

October 12, 2018 by 16 Comments

How do you choose filament when you want strong 3D-printed parts? Like most of us, you probably take a guess, or just use what you have on hand and hope for the best. But armed with a little knowledge on strength of materials, you might be able to make a more educated assessment.

To help you further your armchair mechanical engineer ambitions, [Stefan] has thoughtfully put together this video of tests he conducted to determine the stiffness of common 3D-printing plastics. He’s quick to point out that strength and stiffness are not the same thing, and that stiffness might be more important than strength in some applications. Strength measures how much stress can be applied to an element before it deforms, while stiffness describes how well an element returns to its original state after being stressed. The test rig [Stefan] built for the video analyzes stiffness by measuring the deflection of printed parts under increasing loads. Graphing the applied force versus the deflection gives an indication of the rigidity of the part, while taking the thickness of the material into account yields the bending modulus. The results are not terribly surprising, with polypropylene being the floppiest material and exotic composite filaments, like glass fiber or even “nanodiamond” reinforced PLA coming out as the stiffest. PLA, the workhorse filament, comes in around the middle of the pack.

[Stefan] did some great work here, but as he points out, in the final analysis it almost doesn’t matter what the stiffness and strength of the filament are since you can easily change your design and add more material where it’s needed. That only works up to a point, of course, but it’s one of the many advantages of additive manufacturing.

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An Open Source Toy Synth

October 12, 2018 by 9 Comments

If you thought the future of electronic musical instruments was massive Emerson-class modular synths, giant MPCs with pads the size of Dance Dance Revolution machines, or hilariously expensive polysynths, you couldn’t be more wrong. The future is, effectively, toys. Those tiny little Korgs you can stuff in your pocket are selling like hot cakes, and Pocket Operators are king of the hill. One of the more interesting musical toys is the Organelle, an aluminum enclosure with maple buttons laid out in a keyboard configuration. It’s a synth, it’s a sound engine, and it does produce some interesting noises. All the software is Open Source, but the hardware isn’t. That leaves it up to someone else to make the hardware for the rest of us. That’s exactly what [mitchell] is doing for his Hackaday Prize entry.

The core of this build is a Nanopi Neo Core, or basically an Allwinner H3 breakout board with 256 MB of RAM running at 1.2 GHz. This runs the basic Organelle scripts, and has all the drivers to become a MIDI device. Added to that, there’s a DAC, a small TFT screen, an STM32F103 for reading the buttons, encoders, and pots, a sound card, a USB hub IC, and a battery torn from a Kindle.

The idea for this project is to have something along the lines of the Teenage Engineering OP-1, another of the very fancy ‘toy’ synths, but also to build something that anyone else can build. [mitchell] is just about there, and the prototype PCB he made actually works. There’s still a lot more work to do, but this is an exceptionally interesting project we can’t wait to see hit prime time.

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Logic Analyzers For FPGAs: A Verilog Odyssey

October 12, 2018 by 10 Comments

Sometimes you start something simple and then it just leads to a chain reaction of things. I wanted to write a post about doing state machines in Verilog and target the Lattice iCEstick board that we often use for quick FPGA projects. That led to a small problem: how do you show what’s going on inside? In this series of posts, we’ll look at building a logic analyzer into an FPGA to help debug itself, instantiating memory, and — finally — state machines.

Logic analysis is a common tool in FPGA development. If you use Altera, they have Signal Tap available that lets you build a simple logic analyzer into the FPGA that talks back to your PC. Xilinx has ChipScope which is about the same. Sometimes those tools either cost money or are limited in some way in the free versions. I have my sights set on a tool that can be used with the Lattice architecture.

Sure, you can ship data out on I/O pins and then use a regular logic analyzer to pick up the data. But that isn’t very handy. So I thought about writing a generic logic analyzer component. But before I did I decided to check to see if someone else had already done it.

Spoiler alert: they did, but I wanted something a little different so I wound up extending the program significantly. What I wound up with is a reasonably portable Verilog logic analyzer that can produce traces like this one:

Keep in mind, this isn’t a simulation. This is real data pulled off the actual FPGA. Yes, that is gtkwave producing the plots, but the input data is a VCD file generated from samples taken inside the FPGA.

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Contest Results: Raspberry Pis Put On A Show

October 12, 2018 by 1 Comment

Some of the most satisfying projects of all are the ones that do something visual. All the network routers, data loggers, and thermostats are great. But we are visual creatures and even a humble blinking LED is enough to give you a little rush even compared to finding a large prime number. We wanted to see what our community could do visually with a Raspberry Pi so we challenged you with the Visualize it with Pi contest.

As always, the competition was brisk, with a lot of great projects. This contest showed off the trend towards using LED modules and assemblies to add visuals to projects. Why not? They are cheap enough and a well-integrated module can make a project simple to wire and integrate.

We didn’t see as many media-related projects as you might expect, although there was one tied into Stranger Things, one to Tron, and the virtual reality lighting project did have some Star Wars images. Projects ranged from the practical storage box labels to the whimsical lemonade bottle that strobes to the beat of the music. If none of that is hardcore enough for you, there was even a Raspberry Pi-controlled radio telescope. You can find all the entries over on Hackaday.io. Now let’s see which entries managed to turn the head of the judging panel.

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Down The DIY Rabbit Hole With A Shop AC Installation

October 12, 2018 by 50 Comments

There’s a fine line between a successful DIY project and one that ends in heartbreak. It’s subjective too; aside from projects that end up with fire trucks or ambulances in the driveway, what one DIYer would consider a disaster might be considered a great learning opportunity to someone else.

We’re pretty sure [Cressel] looks at his recent DIY mini-split AC installation for his shop as a series of teachable moments. Most folks leave HVAC work to the pros, but when you run a popular YouTube channel where you make your own lathe from scratch, you might be persuaded to give anything a go. [Cressel] did everything possible to do this job like a pro, going so far as to get training in the safe handling of refrigerants and an EPA certification so he knew how to charge the system correctly. He also sunk quite a bit of money into tools; between the manifold gauge set, vacuum pump, and various plumbing bits, that was a hefty $300 bite alone.

The install went well until he started charging the refrigerant, when a mistake with a fitting caused him to contaminate his nice, new batch of R-410A. Rather than back out and call a pro to finish up, [Cressel] stuck with it, to the tune of $900 in extra tools and materials needed to recover the old refrigerant safely and replace it with virgin R-410A. The video below has a condensed version of the whole tale.

It all worked out in the end, but at a cost that probably meets or exceeds what an HVAC contractor would have charged. [Cressel] seems like a glass-half-full kind of guy, though, so we expect he’s happy to have learned something new, and to have a bunch of neat new tools to boot.

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Retrotechtacular: Robots And Bowling Pins

October 12, 2018 by 11 Comments

On a recent bowling excursion it occurred to us that this is one of the most advanced robotics systems most Americans will directly interact with. That’s a bold claim today, but certainly one that was correct decades ago. Let’s take a stroll back to 1963 for a look at the state of the art in bowling at the time, the AMF automatic pinspotter.

With their basis in industrial automation, bowling was a perfect problem for the American Machine and Foundry company (AMF) to take on. Their business began at the turn of the 20th century with automated cigarette manufacturing before turning their sights on bowling pins after the second world war. The challenge involves more than you might think as pinspotters are confined to a narrow area and need to work with oddly-shaped pins, the bowling ball itself, and deal with setting up fresh frames but also clearing out the field after the first roll.

Separating the ball from the pins is handled by gravity and an oscillating plunger that pushes errant pins back onto a conveyor. That conveyor stretches the width of the lane and moves pins back to a pin elevator — a wheel moving perpendicular to the ground with orients and raises them to a swiveling conveyor belt that can drop them into the setting jig waiting for the next full frame setup.

Everything in this promo video has jargon which is just delightful. We especially enjoyed the non-mechanical mention of how the machine “clears dead wood from the pin deck”. We could watch this kind of automation all day, and in fact found some other gems while searching about. Here’s a more recent look a the AMF 82-70 (the same model as in the promo video). We also wondered about manual pinspotting and found this manual-with-mechanical-assist setup to be interesting despite the audio.

Much to our surprise we’ve featured AMF in a Retrotectacular article before. Once their bowling automation started to take off, they set their sights on restaurant automation. Looks like Brian Benchoff’s visit to the robo-hamburger joint was actually a retro experience!

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You Should Not Try These Taser NERF Darts

October 12, 2018 by 23 Comments

For most of us, a good part of our childhood involved running around someone’s backyard (or inside the house) trying to score hits with a toy NERF gun. The fun level was high and the risk of personal injury was low. Now that we’re all mostly adults, it’s probably time to take our NERF game to the next level with some risk of serious personal harm.

In an effort to help his brother get back at him for being somewhat of a bully in their youth, [Allen Pan] gifted him with an upgraded NERF gun. Specifically, one with darts that pack a punch. Each of the “Elite” darts was equipped with a 300 V capacitor packed into the interior of the dart. New tips were 3D printed with special metal tips that allow the capacitor to discharge upon impact.

Besides the danger, there’s a good bit of science involved. Parts were scavenged from a new (and surprisingly expensive) disposable camera, and a customized circuit was constructed around the barrel of the dart gun that allows the darts to charge up when they’re loaded. It’s an impressive build that would be relatively simple to reconstruct for yourself, but it’s probably not the worst thing we’ve seen done with high voltage and a few small capacitors.

Thanks to [Itay] for the tip!

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