Linux Fu: The Chrome OS Flex Virtualization

The Flex Desktop is user-friendly and responsive

You’ve probably heard about Google Chromebooks. Like Android, Chrome OS is based on some variant of Linux, but it is targeted at the “cloud first” strategy so Chromebooks typically don’t have a huge amount of storage or compute power. If you have a real Chromebook, you can also use it to run certain other kinds of programs via virtualization. However, Google has recently pushed out Chrome OS Flex which is meant to install on a spare laptop you might happen to have hanging around. Seems attractive to take that only Windows 7 laptop and repurpose it to run Chrome OS, especially if you can run Linux apps on it. Unfortunately, Chrome OS Flex has a very different use case and I would only recommend installing it if you meet the exact use case it addresses.

The other option, of course, is to just install Linux on that old hardware. There are several distributions that are made for that purpose and, honestly, even most of the major distributions will work fine on older hardware with a little tweaking to turn off some of the more resource-costly features. That assumes you know how to install, tweak, and maintain Linux.

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The eurorack rail piece, just printed in white plastic, not yet folded, with a folded example in the upper right corner

Bend Your Prints To Eliminate Supports

When designing even a reasonably simple 3D-printable part, you need to account for all the supports it will require to print well. Strategic offsetting, chamfering, and filleting are firmly in our toolkits. Over time we’ve learned to dial our settings in so that, hopefully, we don’t have to fumble around with a xacto knife after the bed has cooled down. On Twitter, Chris shows off his foldable 3D print experiments (nitter) that work around the support problem by printing the part as a single piece able to fold into a block as soon as you pop it off the bed.

The main components of this trick seem to be the shape of the place where the print will fold, and the alignment of bottom layer lines perpendicular to the direction of the fold lines. [Chris] shows a cross-section of his FreeCad design, sharing the dimensions he has found to work best.

Of course, this is Twitter, so other hackers are making suggestions to improve the design — like this sketch of a captive wedge likely to improve alignment. As for layer line direction alignment, [Chris] admits to winging it by rotating the part in the slicer until the layer lines are oriented just right. People have been experimenting with this for some time now, and tricks like these are always a welcome addition to our toolkits. You might be wondering – what kinds of projects are such hinges useful for?

The example Chris provides is a Eurorack rail segment — due to the kind of overhangs required, you’d be inclined to print it vertically, taking a hit to the print time and introducing structural weaknesses. With this trick, you absolutely don’t have to! You can also go way further and 3D print a single-piece foldable Raspberry Pi Zero case, available on Printables, with only two extra endcaps somewhat required to hold it together.

Foldable 3D prints aren’t new, though we typically see them done with print-in-place hinges that are technically separate pieces. This trick is a radical solution to avoiding supports and any piece separation altogether. In laser cutting, we’ve known about similar techniques for a while, called a “living hinge”, but we generally haven’t extended this technique into 3D printing, save for a few manufacturing-grade techniques. Hinges like these aren’t generally meant to bend many times before they break. It’s possible to work around that, too — last time we talked about this, it was an extensive journey that combined plastic and fabric to produce incredibly small 3D printed robots!

We thank [Chaos] for sharing this with us!

Slipping Sheets Map Multiple Bends In This Ingenious Flex Sensor

When thoughts turn to measuring the degree to which something bends, it’s pretty likely that strain gauges or some kind of encoders on a linkage come to mind. Things could be much simpler in the world of flex measurement, though, if [Fereshteh Shahmiri] and [Paul H. Dietz]’s capacitive multi-bend flex sensor catches on.

This is one of those ideas that seems so obvious that you don’t know why it hasn’t been tried before. The basic idea is to leverage the geometry of layered materials that slip past each other when bent. Think of the way the pages of a hardbound book feather out when you open it, and you’ll get the idea. In the case of the ShArc (“Shift Arc”) sensor, the front and back covers of the book are flexible PCBs with a series of overlapping pads. Between these PCBs are a number of plain polyimide spacer strips. All the strips of the sensor are anchored at one end, and everything is held together with an elastic sleeve. As the ShArc is bent, the positions of the electrodes on the top and bottom layers shift relative to each other, changing the capacitance across them. From the capacitance measurements and the known position of each pad, a microcontroller can easily calculate the bend radius at each point and infer the curvature of the whole strip.

The video below shows how the ShArc works, as well as several applications for the technology. The obvious use as a flex sensor for the human hand is most impressive — it could vastly simplify [Will Cogley]’s biomimetic hand controller — but such sensors could be put to work in any system that bends. And as a bonus, it looks pretty simple to build one at home.

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Flexible PCB Earrings Put The Art In Art Deco

Earrings have been a hackers’ target for electronic attachment for quite a while, but combining the needed components into a package small enough to wear in that finicky location is quite a challenge. If [Sawaiz Syed]’s Art Deco Earrings are anything to go by, ear computers have a bright future ahead of them!

This is a project unusually well described by its name. It is in fact an earring, with art deco styling. But that sells it way too short. This sliver of a flex circuit board is double sided to host an ATtiny, accelerometer, LDO, and eight 2020 formfactor controller-integrated LEDs. Of course it’s motion sensitive, reacting to the wearer’s movement via LED pattern. [Sawaiz] makes reference to wearing it while dancing, and we can’t help but imagine an entire ballroom all aglow with tiny points of LED light.

The Art Deco Earrings are also set apart by the thoroughness of their documentation (have we mentioned how much we love detailed documentation?). [Sawaiz] not only drops the source in your lap, but the README in the Github repo linked at the top walks the reader through each component of the design in detail. Plus the PCBA render is so complete it includes a model of the wire loop to fit through the wearer’s ear; how cool is that? The single piece that’s still in progress is the battery. The earring itself hosts an LDO, so all that is required is stashing a battery somewhere discrete, perhaps in the user’s hair? We’re looking forward to seeing what [Sawaiz] works out.

For the full effect, check out the gif of an assembled unit in action after the break.

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Printed It: Collet Drill Stop

You’d think that being quarantined in your home would be perfect for hackers and makers like us, as we all have a project or two that’s been sitting on the back burner because we didn’t have the time to tackle it. Unfortunately, some are finding that the problem now is actually getting the parts and tools needed to do the job. When there’s a bouncer and a line outside the Home Depot like it’s a nightclub on Saturday night, even the simplest of things can be difficult to source when making in the time of COVID.

Which is exactly the situation I found myself in recently when I needed to drill a bunch of holes to the same depth. The piece was too big to put in the drill press, and while I contemplated just wrapping the bit in some tape to serve as a makeshift stop, I wasn’t convinced it would be accurate or repeatable enough. It occurred to me that a set of drill stop collars would be easy enough to design and 3D print, but before I fired up OpenSCAD, I decided to see what was already available online.

Which is how I found the “Collet Drill Stop” from Adam Harrison. Rather than the traditional ring and setscrew arrangement, his design uses a printable collet that will clamp down on the bit at an arbitrary position without tools. So not only could I avoid a trip to the store by printing this design out, it looked like it would potentially be an upgrade over what I would have bought.

Of course, it’s wise not to take anything for granted when dealing with 3D printing. The only way I could be sure that Adam’s design would work for me was to commit it to plastic and try it out.

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Micro-Sized Flex For Commercial Quality Bodging

We love watching the creativity unleashed by the democratization of once-exotic technologies. The casualness by which one can order a cheap, small run of PCBs has unlocked a flood of fine pitch components and projects which look commercial quality even with a total build volume of one. Now the once mythical flex PCB has been falling from it’s stratospheric pricing and with OSHPark’s offering it feels like we’re at the inflection point. [qwertymodo] leveraged this by creating a beautifully twisted flex to add link port support to the Super Game Boy

In the mid-90’s Nintendo released the Super Game Boy, a cartridge for the SNES which allowed you to play Game Boy games on the big screen. Each cartridge was in fact an entire Game Boy with the appropriate hardware to present it in a way the host console could interface with, but missing some of the hardware a standalone Game Boy would include like a link port to connect it to another system. This mod fixes this limitation by bridging the correct pins out from the CPU to a breakout board which includes the link port connector. For general background on what’s going on here, check out [Brian]’s article from April describing a different mod [qwertymodo] executed to the same system.

What’s fascinating is how elegant the mod is. Using a a flex here to create a completely custom, strangely shaped, one-of-a-kind adapter for this random IC, in low volume is an awesome example of the use of advanced manufacturing techniques to take our hacks to the next level. It reminds us a little of the method [Scotty] used to add the headphone jack to his iPhone 7 back in 2017. At the time that seemed like a technology only available to hackers who could speak a little Mandarin and lived in Shenzhen.

Detailed information on this hack is a little spread out. There is slightly more info in these tweets, and if you have a Super Game Boy crying out for a link port the adapter flexes are sometimes available here. Look beyond the break to see what the mod originally looked like sans-flex.

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These Projects Bent Over Backward To Win The Flexible PCB Contest

Back in March, the call went out: take your wiggliest, floppiest, most dimensionally compliant idea, and show us how it would be better if only you could design it around a flexible PCB. We weren’t even looking for a prototype; all we needed was an idea with perhaps a sketch, even one jotted on the legendary envelope or cocktail napkin.

When we remove constraints like that, it’s interesting to see how people respond. We have to say that the breadth of applications for flex PCBs and the creativity shown in designing them into projects was incredible. We saw everything from circuit sculpture to wearables. Some were strictly utilitarian and others were far more creative. In the end we got 70 entries, and with 60 prizes to be awarded, the odds were ever in your favor.

Now that the entries have been evaluated and the winners decided, it’s time to look over the ways you came up with to put a flexible PCB to work. Normally we list all the winners in our contest wrap-ups, but with so many winners we can’t feature everyone. We’ll just call out a few of the real standout projects here, but you really should check the list of winning projects to see the full range of what this call for flexibility brought out in our community.

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