An Electromagnet Brings Harmony To This Waving Cat

June 1, 2018 by Kerry Scharfglass 9 Comments

We’ve noticed waving cats in restaurants and stores for years, but even the happy bobbing of their arm didn’t really catch our attention. Maybe [Josh] had seen a couple more than we have when it occurred to him to take one apart to see how they work. They are designed to run indoors from unreliable light sources and seem to bob along forever. How do the ubiquitous maneki-neko get endless mechanical motion from one tiny solar cell?

Perhaps unsurprisingly given the prevalence and cost of these devices, the answer is quite simple. The key interaction is between a permanent magnet mounted to the end of the waving arm/pendulum and a many-turn wire coil attached to the body. As the magnet swings over the coil, its movement induces a voltage. A small blob of analog circuitry reacts by running current through the coil. The end effect is that it “senses” the magnet passing by and gives it a little push to keep things moving. As long as there is light the circuit can keep pushing and the pendulum swings forever. If it happens to stop a jolt from the coil starts the pendulum swinging and the rest of the circuit takes over again. [Josh] points to a similar circuit with a very nice write up in an issue of Nuts and Volts for more detail.

We’ve covered [Josh]’s toy teardowns before and always find this category of device particularly interesting. Toys and gadgets like the maneki-neko are often governed by razor-thin profit margins and as such must satisfy an extremely challenging intersection of product constraints, combining simple design and fabrication with just enough reliability to not be a complete disappointment.

For more, watch [Josh] describe his method in person after the break, or try flashing his code to an Arduino and make a waving cat of your own.

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Blowing Arcylic Canopies Using Stuff From Around The Shop

May 31, 2018 by Steven Dufresne 13 Comments

Blowing an acrylic sheet after heating it is an easy way to make a smooth and transparent canopy or bubble for anything from clams to light fixtures. [Michael Barton-Sweeney] does it using plastic blow ovens he made cheaply, mainly from stuff which most of us already have in our workshops.

All you need is a way to heat the plastic, to then clamp it down around the edges, and finally to blow air into it as you would when blowing up a balloon. Of course, there are things to watch out for such as making sure the plastic is heated evenly and letting it cool slowly afterward but he covers all that on his hackaday.io page.

He’s also on his second plastics blow oven. The first one worked very well and is perhaps the easiest to make, building up an enclosure of CMUs (cinder blocks) and brick. He had success heating it with both propane and with electric current run through Kanthal wire. But the CMUs absorbed a lot of heat, slowing down the process. So for his second one he made a cast concrete enclosure with aluminum reflectors inside to focus the heat more to where needed.

We’re not sure of everything he’s blown acrylic bubbles for but we first learned of his ovens from the transparent clams in his underwater distributed sensor network. In fact, he was inspired to do plastics blowing from a childhood memory of the Air Force museum in Dayton, Ohio, where they visited the restoration hanger and watched the restorers blowing bubbles for a B-17 ball turret.

Though if you want to go smaller and simpler for something like a light fixture then you can get away with using a toaster oven, a PVC pipe, and a toilet flange.

Cheap Stuff To Hack: A Router With An SDR For $13

May 30, 2018 by Brian Benchoff 41 Comments

The history of consumer electronics is littered with devices that are relatively uninteresting at first, but become spectacular platforms for hardware exploitation once a few select people figure out how everything ticks. The Linksys WRT54G was just a router until someone figured out how to put a complete Linux system on them. Those RTL-SDR dongles were just for capturing over the air TV until someone realized they were actually a software-defined radio. The CueCat was just dot-com boom marketing garbage until… well, we picked up a lot of CueCats regardless.

Now there’s a new device sitting on the shelves at Walmart just waiting for some Linux hackers to have a go. It’s the Tzumi MagicTV, a device that allows you to watch over-the-air television on your phone. What’s inside? It’s a WiFi router, an RTL-SDR, and a battery pack in one tiny package. The best part? It costs $13, and apparently Walmart is just blowing them out.

Right now, there aren’t too many details on what’s going on inside the Tzumi MagicTV box, however, the discussion over on the RTLSDR subreddit has revealed enough to give us a good idea of what’s going on. The router inside the MagicTV is a TP-Link TL-WR703N, the exact same WiFi router that took the WRT54G’s place as the king of hackable routers a few years ago. The SDR chip is the same as the Astrometa DVB-T2, one of the common TV tuners on-a-stick. Other than that, there are TX and RX pins on the board, SSH is open, no one knows the password, but as of this writing, a few people are putting John the Ripper to work trying to break into this box.

What is the end goal of cracking this Linux box wide open? Well, it’s a WiFi router and an SDR, so if you want to make your own Flightaware ADS-B logger, that could be on the table. Of course, you could actually use it for its intended purpose and pull down over-the-air TV to your local network, but that seems so pedestrian after getting root on a $13 box from Walmart.

Thanks [Adam] for the tip!

Monitoring Air Quality, One Sleepy Meeting At A Time

May 29, 2018 by Dan Maloney 10 Comments

To those of us in the corporate world, the conference room is where hope goes to die. Crammed into a space too small for the number of invitees, the room soon glows with radiated body heat and the aromas of humans as the time from their last shower gradually increases. To say it’s not a recipe for productivity is an understatement at best.

Having suffered through too many of these soporific situations, [Charles Ouweland] took matters into his own hands and built this portable air quality meter for meetings. With an OLED display on top and sensors inside, it displays not only the temperature, humidity, and barometric pressure, but also the CO₂ concentration and the levels of volatile organic compounds (VOC), noxious substances sometimes off-gassed from building materials, furniture upholstery, and coworkers alike.

The monitor quantifies his meeting misery, which we’re sure wins him points with his colleagues. For our part, though, what we find interesting is his design process. He started where many of us would, with an Arduino Uno. The sensor modules, a CCS811 for VOC and CO₂ as well as a BME280 for temperature, humidity, and pressure, both needed 3.3 volts, so he added a regulator to knock the Arduino’s 5-volt supply into range and some MOSFETs for level matching. Things were getting bulky, though, so he set about reducing the component count. The Uno went by stripping out its already programmed MCU. That killed the need for the regulator and MOSFETs, since everything would be happy with 3.3 volts. A few more rounds of optimization led to the final product, compact enough to run on a pair of AA batteries.

This is a great lesson in going from prototype to product. And it’s so compact, it could even ride on top of a Roomba to map the conference room’s floor-level air quality.

A Nicely Crafted POV Lightsaber

May 27, 2018 by Dan Maloney 7 Comments

We need to have a talk. As tough a pill as it is to swallow, we have to face that fact that some of the technology promised to us by Hollywood writers and prop makers just isn’t going to come true. We’re never going to have a flux capacitor, actual hoverboards aren’t a real thing, and nobody is going to have sword fights with laser beams.

But just because we can’t have real versions of these devices doesn’t mean we can’t make our own prop versions with a few value-added features, like this cool persistence-of-vision lightsaber. [Luni], better known around these parts as [Bitluni] and for his eponymous YouTube channel where he performs wizardry like turning an ESP32 into a software-defined television station, shows he’s no slouch at more mechanical builds either. The hardware is standard POV fare, with a gyro to sense the position of the lightsaber hilt and an ESP32 to run the long Neopixel strip in the blade. There’s also a LiPo pack and a biggish DC-DC converter; the latter contributes mightily to the look of the prop, with its large heatsinks that stick out from the end of the aluminum tubing hilt. There’s also a small speaker and amp for the requisite sound effects on startup and shutdown, and the position-sensitive thrumming is a nice touch too. Check out the POV action in the video below.

What’s that you say? You recall seeing a real lightsaber here before? Well, sort of, but that’s pushing things a bit. Or perhaps you’ve got this more destructive version in mind.

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Wireless Charger Gives A Glimpse Into Industrial Design Process

May 26, 2018 by Dan Maloney 15 Comments

Almost every product on the market has been through the hands of an industrial designer at some point in its development. From the phone in your pocket to the car in your driveway or the vacuum in your closet, the way things look and work is the result of a careful design process. Taking a look inside that process, like with this wireless phone charger concept, is fascinating and can yield really valuable design insights.

We’ve featured lots of [Eric Strebel]’s work before, mainly for the great fabrication tips and tricks he offers, like how to get a fine painted finish or the many uses of Bondo. But this time around, he walks us through a condensed version of his design process for a wireless phone charger and stand. His client had specific requirements, like being able to have the phone held up in landscape or portrait mode, so he started with pen and paper and sketched some ideas. A swiveling cylinder seemed to fit the bill, and after a quick mockup in PVC pipe, he started work on a full-size prototype in urethane foam. There are some great fabrication tips in the video below, mainly centered on dealing with not owning a lathe.

The thing for us with all of [Eric]’s videos, but especially this one, is seeing the design process laid out, from beginning to (almost) the end. He sure makes industrial design look like a cool gig, one that would appeal to the Jacks- and Jills-of-all-trades who hang out around here.

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Fail Of The Week: The Semiconductor Lapping Machine That Can’t Lap Straight

May 21, 2018 by Dan Maloney 34 Comments

It seemed like a good idea to build a semiconductor lapping machine from an old hard drive. But there’s just something a little off about [electronupdate]’s build, and we think the Hackaday community might be able to pitch in to help.

For those not into the anatomy and physiology of semiconductors, getting a look at the inside of the chip can reveal valuable information needed to reverse engineer a device, or it can just scratch the itch of curiosity. Lapping (the gentle grinding away of material) is one way to see the layers that make up the silicon die that lies beneath the epoxy. Hard drives designed to spin at 7200 rpm or more hardly seem a suitable spinning surface for a gentle lapping, but [electronupdate] just wanted the platter for its ultra-smooth, ultra-flat surface.

He removed the heads and replaced the original motor with a gear motor and controller to spin the platter at less than 5 rpm. A small holder for the decapped die was fashioned, and pinched between the platter hub and an idler. It gently rotates the die against the abrasive-covered platter as it slowly revolves. But the die wasn’t abrading evenly. He tried a number of different fixtures for the die, but never got to the degree of precision needed to see through the die layer by layer. We wonder if the weight of the die fixture is deflecting the platter a bit?

Failure is a great way to learn, if you can actually figure out where you went wrong. We look to the Hackaday community for some insight. Check out the video below and sound off in the comments if you’ve got any ideas.

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