Author: Elliot Williams

1449 Articles

Your Quadcopter Has Three Propellers Too Many

May 4, 2016 by 50 Comments

While studying failure modes for quadcopters, and how to get them safely to the ground with less than a full quad of propellers, a group of researchers at the Institute for Dynamic Systems and Control at ETH Zurich came up with a great idea: a mode of flight that’s like the controlled spinning descent of a maple seed.

The Monospinner runs on the absolute minimum number of moving parts. Namely, one. Even a normal helicopter has a swash plate for adjustable blade pitch, and a tail rotor to keep it from spinning. Give up the idea that you want to keep it from spinning, and you can achieve controlled flight with a lot less. Well, one motor and a whole lot of math and simulation.

The Monospinner is carefully weighted so that it’s as stable as possible while spinning, but so far it’s unable to spin itself up from a standstill. In initial tests, they attached it to a pivot to help. The best part of the video (below) is when the researcher throws it, spinning, into the air and it eventually stabilizes. Very cool.

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I Am Satoshi Nakamoto

May 3, 2016 by 74 Comments

OK, you got me. I’m not. Neither is Dorian Nakamoto, pictured above, and neither is this [Craig White] guy. Or at least, his supposed proof that he is “Satoshi” doesn’t stand up to scrutiny. Indeed, you can re-create it yourself and pretend to be “Satoshi” too.

If you haven’t been following along, “Satoshi Nakamoto” is the person or group of people who invented Bitcoin, and who holds a decent fortune’s worth of the currency. He’s been exceedingly careful at keeping his identity secret. So much so, that upon hearing another “We Found Satoshi” story in the news, we actually laughed at our wife this morning. But then it was picked up by the BBC and is forthcoming in the Economist. Serious journalism.

Well, if you read the BBC piece, they note that “Security expert Dan Kaminsky said the procedure was almost ‘maliciously resistant’ to validation.” Hint: If Dan “DNSSEC” Kaminsky can’t verify a signature, there’s a good chance it’s not the real deal.

The really embarrassing part is that this [Craig White] character claimed to be Satoshi in December 2015. If he actually were Satoshi, who is probably a cryptographic genius, do you think it would take him five months to figure out a cryptographically sound way of proving his identity? Nope.

So here’s how he did it, according to [Patrick McKenzie]’s GitHub, linked above. There is a hashed secret out there that only “Satoshi” knows. Hashes are one-way functions; they produce a number that’s easy to calculate if you know the original data, but devilishly hard to work from the hash backwards to get the data out. This hashed value is public, and part of the blockchain, so we can be pretty sure that it hasn’t been altered.

[Craig] claimed to have some text from Sartre hashed with “Satoshi’s” key, and that this proves his identity. But instead of providing the hash of the Sartre text, [Craig] apparently substituted a hash from the blockchain. When this supposed Sartre hash is validated against the blockchain, of course, it works. In short, he swapped hashes, and people failed to notice.

So I’m not “Satoshi”, and neither is this guy. Who is? The mystery continues. And given how careful “Satoshi” has been so far, it’s likely to remain so for a long while. But one thing’s for sure, when “he” does choose to reveal himself, it won’t be difficult to verify. After all “Satoshi” knows “Satoshi’s” password.

Image via the BBC, of another guy who isn’t “Satoshi”.

(Late Edit: Here’s another really nice writeup, this one by [ErrataRob].)

Atmel Removes Full-Swing Crystal Oscillator

May 3, 2016 by 56 Comments

It is one of our favorite chips, and the brains behind the Arduino UNO and its clones, and it’s getting a tweak (PDF). The ATmega328 and other megaX8-series chips have undergone a subtle design change that probably won’t affect you, but will cause hours of debugging headaches if it does. So here’s your heads-up. The full-swing oscillator driver circuitry is being removed. As always, there’s good news and bad news.

The older ATmega chips had two different crystal drivers, a low-power one that worked for lower speeds, and higher-current version that would make even recalcitrant crystals with fat loading capacitors sing. This “full-swing” crystal driver was good for 16 MHz and up.

The good news about the change is that the low-power crystal driver has been improved to the point that it’ll drive 16 MHz crystals, so you probably don’t need the full-swing driver anymore unless you’re running the chip at 20 MHz (or higher, you naughty little overclocker).

This is tremendously important for Arduinos, for instance, which run a 16 MHz crystal. Can you imagine the public-relations disaster if future Arduinos just stopped working randomly? Unclear is if this is going to ruin building up a perfboard Arduino as shown in the banner image. The full-swing oscillator was so robust that people were getting away with a lot of hacky designs and sub-optimal loading capacitor choices. Will those continue to work? Time will tell.

The bad news is that if you were using the full-swing oscillator to overcome electrical noise in your environment, you’re going to need to resort to an external oscillator instead of a simple crystal. This will increase parts cost, but might be the right thing to do anyway.

Whenever anyone changes your favorite chip, there’s a predictable kerfuffle on the forums. An Atmel representative said they can get you chips with the full-swing driver with a special order code. We’re thinking that they’re not going to let us special order ten chips, though, so we’re going to have to learn to live with the change.

The ATmega328 has already gotten a makeover, and the new version has improved peripheral devices which are certainly welcome. They don’t have the full-swing oscillator onboard, so you can pick some up now and verify if this change is going to be a problem for you or not. We don’t have any of the new chips to test out just yet.

Thanks to [Ido Gendel] for tipping us off to the change in our comment section! If you have any first-hand experience with the new chips, let us know in the comments and send in a tip anytime you trip over something awesome during your Internet travels.

Amazing Oscilloscope Graphics

May 2, 2016 by 25 Comments

From what we can understand, [ompuco] has built a 2D audio output on top of the Unity game engine, enabling him to output X and Y values from his stereo soundcard straight to an oscilloscope in XY mode. His code simply scans through all the vertexes in the scene and outputs the right voltages into the left and right audio streams. He’s using this to create some pretty incredible animations. Check out the video “additives” below for an example. (See if you can figure out what’s being “added”.)

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UV Photographic Printer Lets You Use Strange Chemistries

May 2, 2016 by 11 Comments

There is a family of old photographic chemistries based on iron compounds which, like the blueprint, are exposed using UV light. Ironically, the digital camera revolution which has made everything else in our photographic lives much easier, has made it harder to experiment around with these alternative methods. [David Brown] is making a UV photographic printer to change that.

[David]’s application has a lot in common with PCB printers that use a UV-sensitive resist, only [David] needs greyscale, and it might also be nice if it could work with wet paper. This makes it a more challenging project than you might think, but we like the cut of [David]’s jib.

Like some of the other UV exposer projects, [David]’s uses a rotating mirror to scan across the to-be photograph’s surface. Unlike the other ones that we’ve seen, the exposer hangs from two linear rails. Other printers move the paper underneath a stationary scanning head, which seems a mechanically simpler arrangement. We’re excited to see how this goes.

There’s a lot of interest in UV PCB printers right now. We’ve seen one made from junked CD-ROM drives on one end of the spectrum to one made by retrofitting a delta robot on the other. And don’t disregard the work done by folks interested in UV-curing 3D printers, either.

Minimal 433 MHz Web Home Automation

May 1, 2016 by 4 Comments

How minimal can a decent home automation setup be? If you need an HTML frontend, you’re going to need a webserver. An ESP8266 will do the trick. And then you need to be able to control your electronics. The cheapest and easiest way to do that is with the ubiquitous 433 MHz remote-controlled outlets and a $1 radio unit from an online auction site. Add in a cheap ESP8266 module, and your total outlay is going to be under $20.

That’s exactly what [Nikos Kantarakias] did. He combined a bunch of available ESP8266 Arduino libraries — one for driving the 433 MHz radio modules, [Paul Stoffregen]’s libraries for keeping time and for setting alarms, and another for keeping track of time zones — with some of his own code for setting up WiFi access, and it’s done.

It’s all available on GitHub for your perusal. The code does some strange things — like requiring a complete reboot every time you set an alarm — but it does let you set recurring and one-off activations of the attached devices with a web interface that’s served off the ESP8266 itself. If you want your coffee machine to turn itself on in the mornings, and want a system that’s easy for the other inhabitants of your house to configure, something like this might be just the ticket.

But if you’re looking for a project on the other end of the ESP-tech spectrum, [CNLohr] wrote a standalone Ethernet controller for the thing. Woah.

Is It A Stepper? Or Is It A Servo?

April 30, 2016 by 37 Comments

Almost everyone who is involved with 3D printing thinks to themselves at some point, “this could all be done using a closed-loop system and DC motors”. Or at least everyone we know. There’s even one commercial printer out there that uses servo control, but because of this it’s not compatible with the rest of the (stepper-motor driven) DIY ecosystem.

[LoboCNC] wanted to change this, and he’s in a unique position to do so, having previously built up a business selling PIC-based servo controllers. His “servololu” is essentially a microcontroller and DC motor driver, with an input for a quadrature encoder for feedback. The micro takes standard step/direction input like you would use to drive a stepper motor, and then servos the attached DC motor to the right position. It even signals when it has an error.
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