Building A Hardware Store Faraday Cage

September 26, 2018 by Tom Nardi 78 Comments

Most Hackaday readers are no doubt familiar with the Faraday cage, at least in name, and nearly everyone owns one: if you’ve ever stood watching a bag of popcorn slowly revolve inside of a microwave, you’be seen Michael Faraday’s 1836 invention in action. Yet despite being such a well known device, the average hacker still doesn’t have one in their arsenal. But why?

It could be that there’s a certain mystique about Faraday cages, an assumption that their construction requires techniques or materials outside the realm of the home hacker. While it’s true that building a perfect Faraday cage for a given frequency involves math and careful attention to detail, putting together a simple model for general purpose use and experimentation turns out to be quick and easy.

As an exercise in minimalist hacking I recently built a basic Faraday cage out of materials sourced from Home Depot, and thought it would be interesting to not only describe its construction but give some ideas as to how one can put it to practical use in the home lab. While it’s hardly a perfect specimen, it clearly works, and it didn’t take anything that can’t be sourced locally pretty much anywhere in the world.

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Trials And Tribulations In Sending Data With Wires

September 25, 2018 by Kerry Scharfglass 14 Comments

When working on a project that needs to send data from place to place the distances involved often dictate the method of sending. Are the two chunks of the system on one PCB? A “vanilla” communication protocol like i2c or SPI is probably fine unless there are more exotic requirements. Are the two components mechanically separated? Do they move around? Do they need to be far apart? Reconfigurable? A trendy answer might be to add Bluetooth Low Energy or WiFi to everything but that obviously comes with a set of costs and drawbacks. What about just using really long wires? [Pat] needed to connect six boards to a central node over distances of several feet and learned a few tricks in the process.

When connecting two nodes together via wires it seems like choosing a protocol and plugging everything in is all that’s required, right? [Pat]’s first set of learnings is about the problems that happen when you try that. It turns out that “long wire” is another way to spell “antenna”, and if you happen to be unlucky enough to catch a passing wave that particular property can fry pins on your micro.

Plus it turns out wires have resistance proportional to their length (who would have though!) so those sharp square clock signals turn into gently rolling hills. Even getting to the point where those rolling hills travel between the two devices requires driving drive the lines harder than the average micro can manage. The solution? A differential pair. Check out the post to learn about one way to do that.

It looks like [Pat] needed to add USB to this witches brew and ended up choosing a pretty strange part from FTDI, the Vinculum II. The VNC2 seemed like a great choice with a rich set of peripherals and two configurable USB Host/Peripheral controllers but it turned out to be a nightmare for development. [Pat]’s writeup of the related troubles is a fun and familiar read. The workaround for an incredible set of undocumented bad behaviors in the SPI peripheral was to add a thick layer of reliability related messaging on top of the physical communication layer. Check out the state machine for a taste, and the original post for a detailed description.

A Three Axis Mill For The End Of The World

September 24, 2018 by Tom Nardi 20 Comments

A mill is one of those things that many hackers want, but unfortunately few get their hands on. Even a low-end mill that can barely rattle its way through a straight cut in a piece of aluminum is likely to cost more than all the other gear on your bench. A good one? Don’t even ask. So if something halfway decent is out of your price range, you might as well throw caution to the wind and build one.

That’s more or less the goal behind this extremely basic three axis mill built by [Michael Langeder]. Designed around a cheap rotary tool, it’s hard to imagine a more simplistic mill. Almost all the components are stuff you could pick up from the local hardware store, or probably even the junk pile if you were really in a pinch. It won’t be the best looking piece of gear in your shop, but it’s good enough to learn the basics on and just might be able to bootstrap a second-generation mill RepRap-style.

Made out of scrap blocks of aluminum and some threaded rod, the Z axis itself represents the bulk of the work on this project. It gives the user fine control over the height of the rotary tool by way of a large knob on the top. It’s held over the work piece with some flat steel bars and corner brackets rather hastily cut out of aluminum sheet.

While the tool holder is 3D printed, you could probably hack something up out of a block of wood if you didn’t have access to a printer. The only part of the mill that’s really “cheating” is the cross slide table, but at least they can be had for relatively cheap. If you really wanted to do this with junk bin finds, you could always replicate the Z axis design for X and Y.

If you’re not looking for something quite so austere, we’ve covered slightly more advanced DIY mills in the past. You could always go in the opposite direction and put a cross slide vise on your drill press, but do so at your own risk.

Chordata motion capture dancer and 3D model

A Motion Capture System For Everyone

September 24, 2018 by Steven Dufresne 23 Comments

[Chordata] is making a motion capture system for everyone to build and so far the results are impressive, enough to have been a finalist in the Hackaday Human Computer Interface Challenge. It started a few years ago as one person’s desire to capture a digital performance of a dancer on a stage and has grown into a community of contributors. The board files and software have just been released as alpha along with some instructions for making it work, though more detailed documentation is on the way.

Fifteen sensor boards, called K-Ceptors, are attached to various points on the body, each containing an LSM9DS1 IMU (Inertial Measurement Unit). The K-Ceptors are wired together while still allowing plenty of freedom to move around. Communication is via I2C to a Raspberry Pi. The Pi then sends the collected data over WiFi to a desktop machine. As you move around, a 3D model of a human figure follows in realtime, displayed on the desktop’s screen using Blender, a popular, free 3D modeling software. Of course, you can do something else with the data if you want, perhaps make a robot move? Check out the overview and the performance by a clearly experienced dancer putting the system through its paces in the video below.

As a side note, the latest log entry on their Hackaday.io page points out that whenever changes are made to the K-Ceptor board, fifteen of them need to be made in order to try it out. To help with that, they show the testbed they made for troubleshooting boards as soon as they come out of the oven.

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The Tiniest Computer Vision Platform Just Got Better

September 23, 2018 by Brian Benchoff 20 Comments

The future, if you believe the ad copy, is a world filled with cameras backed by intelligence, neural nets, and computer vision. Despite the hype, this may actually turn out to be true: drones are getting intelligent cameras, self-driving cars are loaded with them, and in any event it makes a great toy.

That’s what makes this Kickstarter so exciting. It’s a camera module, yes, but there are also some smarts behind it. The OpenMV is a MicroPython-powered machine vision camera that gives your project the power of computer vision without the need to haul a laptop or GPU along for the ride.

The OpenMV actually got its start as a Hackaday Prize entry focused on one simple idea. There are cheap camera modules everywhere, so why not attach a processor to that camera that allows for on-board image processing? The first version of the OpenMV could do face detection at 25 fps, color detection at more than 30 fps, and became the basis for hundreds of different robots loaded up with computer vision.

This crowdfunding campaign is financing the latest version of the OpenMV camera, and there are a lot of changes. The camera module is now removable, meaning the OpenMV now supports global shutter and thermal vision in addition to the usual color/rolling shutter sensor. Since this camera has a faster microcontroller, this latest version can support multi-blob color tracking at 80 fps. With the addition of a FLIR Lepton sensor, this camera does thermal sensing, and thanks to a new library, the OpenMV also does number detection with the help of neural networks.

We’ve seen a lot of builds using the OpenMV camera, and it’s getting ot the point where you can’t compete in an autonomous car race without this hardware. This new version has all the bells and whistles, making it one of the best ways we’ve seen to add computer vision to any hardware project.

Maker Faire NY: Programmable Air

September 22, 2018 by Brian Benchoff 10 Comments

At this year’s World Maker Faire in New York City we’re astonished and proud to run into some of the best projects that are currently in the running for the Hackaday Prize. One of these is Programmable Air, from [Amitabh], and it’s the solution to pneumatics and pressure sensing in Maker and IoT devices.

The idea behind Programmable Air is to create the cheapest, most hacker-friendly system for dealing with inflatable and vacuum-based robotics. Yes, pneumatic robotics might sound weird, but there’s plenty of projects that could make use of a system like this. The Glaucus is one of the greatest soft robotic projects we’ve ever seen, and it turns a bit of silicone into a quadruped robot with no moving parts. The only control you have over this robot is inflating one side or the other while watching this silicone slug slowly crawl forward. This same sort of system can be expanded to a silicone robot tentacle, too.

On display at the Programmable Air booth were three examples of how this device could be used. The first was a simple pressure sensor — a weird silicone pig with some tubing coming out of the nostrils was connected to the Programmable Air module. Squeeze the pig, and some RGB LEDs light up. The second demo was a balloon inflating and deflating automatically. The third demo was a ‘jamming gripper’, basically a balloon filled with rice or coffee grounds, connected to a pump. If you take this balloon, jam it onto an odd-shaped object and suck the air out, it becomes a gripper for a robotic arm. All of these are possible with Programmable Air.

Right now, [Amitabh] has just finalized the design and is getting ready to move into mass production. You can get some updates for this really novel air-powered robotics platform over on the main website, or check out the project over on Hackaday.io.

The Un-Economy Of Building Your Own Spot Welder

September 21, 2018 by Brian Benchoff 47 Comments

If there’s one thing that brings hackers together, it’s the ability to build something for less money than it takes to buy it. It’s an exercise [Great Scott Gadgets] put to the test because he was playing around with some 18650 lithium cells, and had a huge need to put some tabs on batteries. This can be done by soldering, but to do it right you should really use a spot welder. Here’s the rub: you can buy a spot welder for about $250, and you can build one for a little less. So, the question: should [Great Scott] build or buy a spot welder? This wouldn’t be worth reading if he started off with an eBay order.

[Great Scott] designed this spot welder around a half-dozen supercaps, all securely held together with Kapton tape. This goes through a set of MOSFETs, and everything is controlled through an Arduino, a rotary encoder, and a dirt-cheap OLED display. It’s a simple enough circuit but a bit too much for perfboard, so [Great Scott] laid out a PCB and got a few boards for under $40. A bit of solder and some debugging later, and theoretically a spot welder was created.

After all that work, how did the spot welder work? Well, it didn’t. A slight misstep in the schematic meant this board didn’t have reference ground on the MOSFETs, so all this work was for naught. Of course, the only thing required to fix this board was a second board spin, as [Great Scott] probably bought more parts than necessary because that’s what smart people do. Still, he decided to cut his losses and shelve the project.

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