Hardware Hacker’s Marie Kondo: How Many LM386s Is Too Many?

We’re running a contest on Making Tech at Home: building projects out of whatever you’ve got around the house. As a hacker who’s never had a lab outside of my apartment, house, or hackerspace, I had to laugh at the premise. Where the heck else would I hack?

The idea is that you’re constrained to whatever parts you’ve got on hand. But at the risk of sounding like Scrooge McDuck sitting on a mountain of toilet paper, I’ve got literally hundreds of potentiometers in my closet, a couple IMUs, more microcontrollers than you can shake a stick at, and 500 ml of etching solution waiting for me in the bathroom. Switches, motors, timing belts, nichrome wire…maybe I should put in an order for another kilogram of 3D printer filament. In short, unless it’s a specialty part or an eBay module, I’m basically set.

But apparently not everyone is so well endowed. I’ve heard rumors of people who purchase all of the parts for a particular project. That ain’t me. The guru of household minimalism asks us to weigh each object in our possession and ask “does it spark joy?”. And the answer, when I pull out the needed 3.3 V low-dropout regulator and get the project built now instead of three days from now, is “yes”.

And I’m not even a hoarder. (I keep telling myself.) The rule that keeps me on this side of sanity: I have a box for each type of part, and they are essentially fixed. When no more motors fit in the motor box, no more motors are ordered, no matter how sexy, until some project uses enough of them to free up space. It’s worked for the last 20 years, long before any of us had even heard of Marie Kondo.

So if you also sit atop a heap of VFD displays like Smaug under the Lonely Mountain, we want to see what you can do. If you do win, Digi-Key is sending you a $500 goodie box to replenish your stash. But even if you don’t win, you’ve freed up space in the “Robot Stuff” box. That’s like winning, and you deserve some new servos. Keep on hacking!

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Greatest Keycaps And Where To Find Them

Look at your keyboard. Do the keycaps excite you? That’s what we thought. You pound on that thing day in and day out. Shouldn’t it at least be attractive? Or even happiness-inducing? You don’t necessarily have to replace every single keycap to spark joy. When it comes to artisan keycaps, the point is to have something that stands out.

How about an Escape key that looks like a tall stack of flapjacks or a tiny, intricate cream puff? From a practical standpoint, how about a spiky Escape key that makes you think twice about rage quitting?

If you’re into games or anime, chances are good that there are more than enough artisan keycaps out there to keep you cash-poor for a while. The same goes for scrumptious foodstuffs with Cherry MX-compatible stems.

In this day and age, you can get just about any type of keycap you want, especially those encapsulating pop culture phenomena and fads. Yes there’s a fidget spinner keycap, and it’s adorable.

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Dropping A Glider From 18,000 Feet

[Tarik and Kemal] have an objective in mind: to drop a home-made autonomous glider from a high-altitude balloon and safely return it to home. To motivate them, [Tarik] has decided not to cut his hair until they reach 18,000 feet. Given the ambition of their project, it isn’t surprising that his hair is getting rather long now.

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Infinite Flying Glider

If you’ve exhausted your list of electronics projects over the past several weeks of trying to stay at home, it might be time to take a break from all of that and do something off the wall. [PeterSripol] shows us one option by building a few walkalong gliders and trying to get them to fly forever.

Walkalong gliders work by following a small glider, resembling a paper airplane but made from foam, with a large piece of cardboard. The cardboard generates an updraft which allows the glider to remain flying for as long as there’s space for it. [PeterSripol] and his friends try many other techniques to get these tiny gliders, weighing in at around half a gram, to stay aloft for as long as possible, including lighting several dozen tea candles to generate updrafts, using box fans, and other methods.

If you really need some electricity in your projects, the construction of the foam gliders shows a brief build of a hot wire cutting tool using some nichrome wire attached to a piece of wood, and how to assemble the gliders so they are as lightweight as possible. It’s a fun project that’s sure to be at least several hours worth of distraction, or even more if you have a slightly larger foam glider and some spare RC parts.

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Robot Insect Survives Swatting

There is an old saying, that ‘the hand is quicker than the eye;, but somewhat slower than the fly.” However, with a little practice you can swat a fly, although it sometimes doesn’t seem to faze the fly. École polytechnique fédérale de Lausanne (EPFL) has announced they have used nanotech to build a 1 gram possibly untethered, autonomous robotic insect that has enough processing power and sensors to recognize black and white patterns. Artificial muscles provide propulsion. But there’s the kicker: it can survive a strike with a fly swatter.

In the video you see below, the robots can move at 3 centimeters per second and there are two different versions. The first is a tethered system using ultra-thin wires. This is the version that can be folded, smacked, or even squashed by a shoe and continue moving.

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Get Your Acrylic Bends Just Right

Acrylic is a popular material. It’s easy to find, attractive, and available in all manner of colors, thicknesses, and grades. Being a thermoplastic, it’s also simple to apply heat and form it in various different ways. If you’re wanting to build parts out of sheet acrylic, you might find a purpose-built bender useful. [DIY Perspective] built just such a tool to get the job done.

Plywood is used as the base of the tool, and several off-the-shelf hinges are used to make the folding apparatus. Stops are cut out of scrap wood to allow the bender to accurately recreate angles of 45, 90, and 135 degrees. Heat is supplied via a nichrome wire, powered by a laptop power supply and a PWM controller. This allows the temperature of the wire to be controlled, to avoid melting or otherwise damaging the acrylic being bent.

If you find yourself routinely working with acrylic, you might find this tool useful to have around the workshop. Vacuum forming may also be relevant to your interests. Video after the break.

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Arduino-Powered Rocket Test Stand

If you’re into amateur rocketry, you pretty quickly outgrow the dinky little Estes motors that they sell in the toy stores. Many hobbyists move on to building their own homebrew solid rocket motors and experimenting with propellant mixtures, but it’s difficult to know if you’re on the right track unless you have a way to quantify the thrust you’re getting. [ElementalMaker] decided he’d finally hit the point where he needed to put together a low-cost test stand for his motors, and luckily for us decided to document the process and the results.

The heart of the stand is a common load cell (the sort of thing you’d find in a digital scale) coupled with a HX711 amplifier board mounted between two plates, with a small section of vertical PVC pipe attached to the topmost plate to serve as a motor mount. This configuration is capable of measuring up to 10 kilograms with an 80Hz sample rate, which is critically important as these type of rocket motors only burn for a few seconds to begin with. The sensor produces hundreds of data points during the short duration of the burn, which is perfect for graphing the motor’s thrust curve over time.

Given such a small window in which to make measurements, [ElementalMaker] didn’t want to leave anything to chance. So rather than manually igniting the motor and triggering the data collection, the stand’s onboard Arduino does both automatically. Pressing the red button on the stand starts a countdown procedure complete with flashing LED, after which a relay is used to energize a nichrome wire “electronic match” stuck inside the motor.

In the video after the break you can see that [ElementalMaker] initially had some trouble getting the Arduino to fire off the igniter, and eventually tracked the issue down to an overabundance of current that was blowing the nichrome wire too fast. Swapping out the big lead acid battery he was originally using with a simple 9V battery solved the problem, and afterwards his first test burns on the stand were complete successes.

If model rockets are your kind of thing, we’ve got plenty of content here to keep you busy. In the past we’ve covered building your own solid rocket motors as well as the electronic igniters to fire them off, and even a wireless test stand that lets you get a bit farther from the action at T-0.

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