Author: Dan Maloney

3304 Articles

Alternator Becomes Motor For This Electric Go-kart

August 14, 2016 by 49 Comments

Growing up in the 70s and 80s, a go-kart was a quick ticket to coolness, second maybe to a mini-bike. In both cases, a welded steel tube frame and a cast-off lawnmower engine were all that stood between you and neighborhood glory. Looks like a couple of engineering students caught the retro juvenile delinquent bug and built this electric go-kart for their final project.

While the frame for [Adrian Georgescu] and [Masoud Johnson]’s build was a second-hand find, the powertrain is all custom. They targeted a power output of 3 kW but found no affordable motors in that range. So, in true hacker fashion, they rolled their own motor from a used Subaru alternator. The three-phase motor controller came from an electric scooter, three LiPo packs provide the juice, and a pair of Arduinos takes care of throttle control, speed sensing, and sending data to the virtual dashboard on an Android phone. Some lights and a snappy red and black paint job finished off the build. While the video below shows that the acceleration isn’t exactly neck-snapping in the Tesla style, the e-kart can build up to a good speed – 53 km/h. Not too shabby, and no deafening engine right behind your head.

If you’ve got the e-kart bug, best check out some of our previous posts, like this kart built from off-the-shelf components, or this four-wheel-drive mini-kart. Any way you build it, you’ll rule the cul-de-sac.

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Hacking When It Counts: Spy Radios

August 12, 2016 by 33 Comments

World War II can be thought of as the first electronic war. Radio technology was firmly established commercially by the late 1930s and poised to make huge contributions to the prosecution of the war on all sides. Radio was rapidly adopted into the battlefield, which led to advancements in miniaturization and ruggedization of previously bulky and fragile vacuum tube gear. Radios were soon being used for everything from coordinating battlefield units to detonating anti-aircraft artillery shells.

But it was not just the battlefields of WWII that benefitted from radio technology. From apartments in Berlin to farmhouses in France, covert agents toiled away over sophisticated transceivers, keying in coded messages and listening for instructions. Spy radios were key clandestine assets, both during the war and later during the Cold War. Continue reading “Hacking When It Counts: Spy Radios” →

Single Motor Lets This Robot Do The Worm

August 7, 2016 by 17 Comments

With more and more research in the field of autonomous robotics, new methods of locomotion are coming on the scene at a rapid pace. Forget wheels and tracks, forget bi-, quad-, hexa- and octopods, and forget fancy rolling BB-8 clones. If you want to get a mini robot moving, maybe you should teach it to do the worm.

Neither the Gizmodo article nor the abstract of [David Zarrouk]’s paper gives too many details on the construction of this vermiform robot, but there are some clues to be gleaned from the video below. At the 1:41 mark we see the secret of the design – a long corkscrew in the center of the 3D-printed linkages.
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Arduino Replaces Bad AC Thermostat, Hacker Stays Cool

August 5, 2016 by 16 Comments

Most of North America has been locked in a record-setting heat wave for the last two weeks, and cheap window AC units are flying out of the local big-box stores. Not all of these discount units undergo rigorous QC before sailing across the Pacific, though, and a few wonky thermostats are sure to get through. But with a little sweat-equity you can fix it with this Arduino thermostat and temperature display.

We’ll stipulate that an Arduino may be overkill for this application and that microcontrollers don’t belong in every project. But if it’s what you’ve got on hand, and you’re sick of waking up in a pool of sweat, then it’s a perfectly acceptable solution. It looks like [Engineering Nonsense] got lucky and had a unit with a low-current power switch, allowing him to use a small relay to control the AC. The control algorithm is simple enough – accept a setpoint from an encoder, read the temperature sensor, and turn the AC on or off accordingly. Setpoint and current temperature are displayed on an OLED screen. One improvement we’d suggest is adding a three-minute delay between power cycles like the faceplate of the AC states.

This project bears some resemblance to this Arduino-controlled AC, but it seems more hackish to us. And that’s a good thing – hackers have to keep cool somehow.

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Fail Of The Week: Magnetic Flow Measurement Gone Wrong

July 29, 2016 by 42 Comments

Physics gives us the basic tools needed to understand the universe, but turning theory into something useful is how engineers make their living. Pushing on that boundary is the subject of this week’s Fail of the Week, wherein we follow the travails of making a working magnetic flowmeter (YouTube, embedded below).

Theory suggests that measuring fluid flow should be simple. After all, sticking a magnetic paddle wheel into a fluid stream and counting pulses with a reed switch or Hall sensor is pretty straightforward, right? In this case, though, [Grady] of Practical Engineering starts out with a much more complicated flow measurement modality – electromagnetic detection. He does a great job of explaining Faraday’s Law of Induction and how a fluid can be the conductor that moves through a magnetic field and has a measurable current induced in it. The current should be proportional to the velocity of the fluid, so it should be a snap to whip up a homebrew magnetic flowmeter, right? Nope – despite valiant effort, [Grady] was never able to get a usable signal out of the noise in his system. 

The theory is sound, his test rig looks workable, and he’s got some pretty decent instrumentation. So where did [Grady] go wrong? Could he clean up the signal with a better instrumentation amp? What would happen if he changed the process fluid to something more conductive, like salt water? By his own admission, electrical engineering is not his strong suit – he’s a civil engineer by trade. Think you can clean up that signal? Let us know in the comments section. 

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All-terrain Hoverboard Junk Pile Build

July 28, 2016 by 21 Comments

If you’re anything like us, chances are pretty good you’ve got at least one underused piece of fitness gear cluttering up your place. Rather than admit defeat on that New Year’s Resolution purchase, why not harvest the guts and build an all-terrain hoverboard for a little outdoor fun?

The fitness machine in question for [MakeItExtreme]’s build was a discarded Crazy Fit vibration platform. We’re not sure we see the fitness benefits of the original machine, but there’s no doubt it yielded plenty of goodies. The motor and drive belt look stout, and the control board eventually made it into the hoverboard too. The custom steel frame was fabricated using some of [MakeItExtreme]’s DIY tools, which is what we’re used to seeing them build — check out their sand blaster and spot welder for examples. A couple of knobby tires in the center of the board let the rider balance (there’s no gyro in this version) and power is provided by a couple of 12 volt AGM batteries. Sadly, the motor was a line voltage unit, so an inverter was needed. But it was the only part that had to be purchased, making this a pretty complete junk pile build.

See the video after the break for build details and a few test rides. Looks like it can do 20 mph or so – pretty impressive.

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Pressure-formed Parabolic Mirror From A Mylar Blanket

July 26, 2016 by 76 Comments

Parabolic reflectors are pretty handy devices. Whether you’re building a microwave antenna or a long-distance directional microphone, suitable commercial dishes aren’t that hard to come by. But a big, shiny mirror for your solar death-ray needs is another matter, which is where this pressure-formed space blanket mirror might come in handy.

Pressure-forming was a great choice for [NighthawkInLight]’s mirror. We’ve covered pressure-formed plastic domes before, and this process is similar. A sheet of PVC with a recessed air fitting forms the platen. The metallized Mylar space blanket, stretched across a wooden frame to pull out the wrinkles and folds, is applied to a circle of epoxy on the platen. After curing, a few puffs with a bicycle tire pump forms the curve and stretches the film even smoother. [NighthawkInLight]’s first attempt at supporting the film with spray foam insulation was a bust, but the later attempt with fiberglass mesh worked great. A little edge support for the resulting shiny taco shell and the mirror was capable of the required degree of destructive potential.

We doubt this process can be optimized enough to produce astronomy-grade mirrors for visible light, but it still has a lot of potential applications. Maybe a fiberglass radio astronomy dish could be pressure-formed directly with a rig like this?