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  • New Tumblr: Installation-A-Day

    A couple weeks ago, I started a new tumblr, Installation-A-Day, to showcase neat art installations I come across in my travels. You can also follow it on Twitter. It’s still in the formative stages, so any feedback is appreciated. I’m trying to be democratic about what I post there — basically, I just want to showcase people putting themselves and their ideas out into the world. Lots of people have cool ideas, but not everyone has the resources to make slick, DSLR films about them.

    I hope you check it out and enjoy it, and maybe even submit your own work.

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  • The Future of Drones…

    My friend Phil loves to talk about drones. There will be drones in the future, he says: drones will deliver the mail, drones will be used to gather news, etc. He sure does love them drones. So here’s a list of a few things I think drones will do in the future.

    Drones will…

    … direct traffic: There is an accident or fuel spill or something on a highway. The police car rolls up: now the officer has to investigate the situation _and_ control/avoid the traffic at the same time, or wait for a second officer to show up. In the future, a drone — launched from the roof of a police car or emergency vehicle and equipped with a suspended blinky sign — will hover in place keeping traffic a safe distance away. The message on the sign will be remotely controlled by the officer (who can update it in real time) and it will tell you what’s going on: “keep to the left” or “slow down, accident ahead” or “oil on roadway: proceed with caution”, etc. They could also provide temporary traffic signals in the case of a power outage, where the regular stoplights might cease to function.

    … help firefighters working structure fires: Drones will go airborne and scope out a burning building from above, allowing a bird’s eye view of the fire and helping track how it spreads. A camera (possibly IR) feed relayed to the ground will be useful in detecting an impending roof collapse or locating trapped survivors that the firefighters on the ground cannot see. These drones might also carry grappling hook ropes into position, to aid in either pulling a building down or providing an escape route. In addition, they will…

    … be equipped with powerful lights. This can be used in emergency situations for lighting large, outdoor areas quickly. It can also be used by filmmakers and photographers to provide high-angle focused or diffused light sources. I can’t tell you how many shoots I’ve done where I wished for an easily positioned (and controllable) overhead light.

    … build sandbag levees: Heavy-duty drones will be given the repetitive and arduous task of building sandbag levees before an impending flood. Structure building drones already exist, and this is a natural extension of such capability. This frees up human volunteers to concentrate on other areas, such as evacuation.

    … clean windows on the upper floors of buildings: because it’s really cold up there.

    … transport clean water: one of the biggest problems in developing countries is the lack of fresh, clean water. Contaminated or dirty water causes all sorts of diseases, including dysentery, but often sources of clean water are a day’s walk away or more. Sometimes pipelines are not an option either, due to geography or other barriers. Water-bearing drones (“aquarians”) can be used to carry water from the clean sources to the people who need it.

    … decorate very large Christmas trees: in my lifetime, I expect to see the tree at Rockefeller Center get this treatment, after which I will eat some astronaut ice cream on my hover-yacht, while watching my totally open-source TV (because it’s the future, yo).

    … inspect high-tension power and telephone lines: this is currently done by people in helicopters, and it is quite dangerous. Drones don’t care, because drones are fearless.

    … deliver takeout food: until we get widespread replication technology, we’ll have drones. Drones are naturally suited to delivering small, uniform packages (like Bento boxes, for example). I imagine something along the lines of the Indian Dabbawala industry, which is a vast delivery network for lunchtime food that uses uniform payload containers and an efficient routing system to make the rounds. Eventually, your lunchtime lo mein will eventually be delivered to you by an autonomous flying robot.

    … chase away birds at airports: birds getting sucked into jet engines poses a serious safety risk, particularly on takeoff and landing. This problem is currently dealt with by using decoys or actively hunting the birds. A squadron of drones could be useful flying around in pseudo-random low-level patterns and generally creating an unfriendly environment for the birds.

    … become integral tools of augmented reality: I’ve had this idea kicking around in my head for a bit about using drones for augmented reality. The Parrot AR (in all its photo studio glory, above) is one type of ARdrone — the HD camera and smartphone control allow you to augment your reality by giving yourself a new point of perspective. My idea is nothing like that, really. Rather, I’m imagining fog machines mounted on drones (downdraft turbulence problems anticipated). There’s one set of drones which drop a sheet of fog and emit sound, and another set which projects images or movies onto said fog sheet. This means you could deploy actors anywhere on earth, and have them play out some narrative. For whatever reason, the spark for this idea was the Marty Robbins song El Paso*. I imagine an army of drones playing out this whole tragedy across the breadth of the West Texas desert. First in the cantina, where we see the dancing Falina in her grand dress and the gunfight, then the subsequent flight across the desert, and finally (dramatic pause) the inevitable return and puff of smoke from the fatal shot. This idea in particular has the potential to go from avant-garde to mass production very quickly.

    Now, obviously, we need to refine drone technology a bit to accomplish a lot of these things. For example, current (affordable, non-military) drones are not stable in high crosswinds. For the firefighting example above, they will also need to be stable in the presence of strong thermal updrafts and higher temps. In the case of the levee construction drones, they will need to be able to operate in the rain as well, and lift loads upwards of 50 pounds. I’m confident all of these problems will be solved, though, because the initial research cost pales in comparison to the savings and efficiency increase, as well as added safety. So there you have it. If you have your own ideas about things drones can be used for, post them up in the comments!

    *this is a great song musically, and the lyrics are well-written, but I could do without the ‘woman as evil temptress’ trope.

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  • Oscilloscope Christmas Tree

    When I was a little kid, my dad worked at Bell Labs. Every year around Christmas, we’d go visit him at work. One memory which has always stuck with me from my holiday visits was seeing a Christmas tree on an oscilloscope. I was pretty amazed by it. Engineers are a funny bunch — they tend to celebrate holidays in the most uniquely nerdy and wonderful ways, just like kids. When I recently acquired a new ‘scope and wanted to familiarize myself with it, I knew exactly what my test circuit was going to be.

    In honor of the nameless BTL engineer whose scope scribbling captivated me as a child, here we are. Maybe the same thing will happen for some other kid. There are a lot of holiday parties coming up. You could put this on one of your scopes at work or at your hackerspace, and some other kid will see it, and it’ll fire their imagination too. It looks pretty neat at any rate, and it’s downright fascinating after a few fortified egg nogs.

    While I suspect the original was built with 74xx logic circuits, or maybe a couple 555’s (you could easily make a Christmas tree shape by combining triangle (x) and sawtooth (y) waveforms), this one uses an AVR ATTiny2313. (I used my handy BB313 board). You could do this with an Arduino too (that is covered below) — pretty much anything that has an 8-bit timer with dual PWM outputs will do the job. The discussion will apply regardless of the implementation (though the numbers might change).

    Before you continue, bear in mind that I assume you already know how to use an oscilloscope: how to attach the probes, adjust the voltage ranges, put it in XY mode, etc.

    The ATTiny code is here, and this is the schematic for the circuit:

    How it works:

    The PWM outputs feed two RC low-pass filter circuits, with a time constant chosen to effectively suppress the jitter from the rectangular waveforms. The PWM outputs (and hence the DC components of the signals) jump from one point in the drawing to the next; in order to actually draw lines to make the tree shape, you have to interpolate between those points. The delay between one ‘drawing’ point and the next has to be chosen to allow the charge/discharge curve of the RC circuit to do the interpolation. You’ll notice in the photo above that the ‘straight’ lines are slightly curved. This is the because the jumps in x don’t quite equal the jumps in y. You’ll also notice that the tree appears a bit crooked. This is the result of the RC curve not settling out completely before the next transition — the voltages never quite get to where they’re supposed to go before they switch to a new value. Personally, I rather like these imperfections — the tree has a hand-drawn quality to it, like a homemade ornament. You could make the lines straighter and the drawing more uniform by using a longer delay, but it will lower the overall refresh rate, resulting in noticeable flicker. How you draw your oscilloscope Christmas tree says a lot about your personality.

    The ATTiny’s clock is running off of a ceramic resonator at 16MHz. The PWM frequency is 16MHz/256 or 62.5kHz. The corner frequency of the filter is 160Hz, which is about 8.5 octaves (2.5 decades) below that. I used 10k resistors and 0.1uF caps here — you could also use any other “equivalent” RC combo (100k/0.01uF or 1k/1uF, etc.) If you choose to use a chip with a different clock frequency, then you’ll have to adjust the RC circuit accordingly.

    Reducing the capacitor values (or increasing the resistor values) will shift the corner frequency of the filter up, and you’ll start to see the lines get crooked, like resistors in a schematic. These are triangle waves resulting from filtering the rectangular PWM signal. This can look pretty cool too, actually, as below where I switched to 0.022uF capacitors.

    Now the tree has needles, and all it took was changing the coefficients of a partial differential equation — easy! (this might be a great way to introduce a kid to the concept of filtering — just sayin’).

    Arduino Implementation:

    Doing this on an Arduino isn’t much different than using the ATTiny, except that it’s more expensive and instead of a real schematic, you have to read this ridiculous handy cartoon (above).*

    The Arduino code is here. It uses no libraries, so all you have to do is extract the folder into your Arduino directory, set up your oscilloscope and load the sketch.

    Possible alternative methods:

    • If you really, really want a perfect, orthogonal tree, you can use an R2R ladder or dedicated DAC/soundcard to generate the control voltages.
    • You can get straighter lines if you use a current mirror to feed the RC circuit, thus making it a “true” integrator with a straight-line slope.
    • If you want to increase the refresh rate, you could set an upper limit on the 8-bit timer to a lower value, say 64, and set all your points therein. Note on the ATTiny you’ll probably have to do this using an interrupt from the other timer, but it would give you faster PWM output, which means you can use a smaller filter time constant and thus a higher refresh rate.
    • …or, you could overclock the AVR (you know you’ve always wanted to).
    • As I mentioned in the beginning, you might be able to do something like this with a couple of 555’s generating triangle and sawtooth waveforms. If you get their phases matched correctly and with the right frequency ratio, you could have a pretty nice looking tree!

    Be as creative as you like with it — I hope you enjoy making it work for you.

    Merry Christmas!

    *just kidding — I love Arduino! Buon Natale!


    UPDATE – Several folks have done this themselves and written in:

    EmbeddedEric did an awesome Frosty the Snowman with his daughters.

    aussie_nick did one using a DSO.

    Goran did one for the Calgary On-Air Engineers.

    Gordon Pearce took it to the next level with animation using sine functions:


    UPDATE 2: Eva Valesky has kindly translated this page into Macedonian. Thanks, Eva!

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  • Showing Off My Halloween Project On Tonight’s @adafruit Show+Tell

    Behold, the Auto-Loupe!

    This is my latest project: part Halloween costume, part optics hack, and part embedded mechatronics, I call it the Auto-Loupe. I’m showing it off tonight on Adafruit’s Show+Tell show, and will be documenting it over the coming weeks.

    Tune in and check it out!

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  • Atari Punch Console

    Somehow I forgot to post this on my own blog, though I posted it on Adafruit. About a month ago I built this variation on the Atari Punk Console, which I called the “Atari Punch Console.” It was a fun little lark, but as soon as I built it, I starting considering improvements. Stay tuned.


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  • Replicating Captain Picard’s Teacup

    note: images are not at the same scale

    The connection is often made between 3D printing and the replicator technology of Star Trek: The Next Generation. The replicator is an ubiquitous part of daily life in the TNG universe, and often serves as a useful plot device for the show as well. For the show’s entire run, by far, the most replicated thing on screen was Captain Picard’s cup of Earl Grey tea.

    We’ve a ways to go before we can instantly assemble molecules into a hot beverage (and the cup to contain it) using directed energy fields –but– we can make a rough facsimile. So I made one. This is a model of the cup that materializes when Jean-Luc Picard orders his tea. I based the model on the images found here. The original item is made of glass, which is out of reach for most 3D printers at the moment, though I suspect that will change in the future. I believe the original handle is ABS. The handle snaps into that radiused channel in the middle of the cup.

    So there you go — now you too can “replicate” your own cup of “Tea–Earl Grey–Hot!”

    NOTE: This is not intended as an actual drinking vessel — it’s just a prop. Don’t drink stuff out of it, for crying out loud.

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  • Scotch Yoke Steam Engine on Adafruit Show+Tell Tonight

    Barring any technical difficulties, I’ll be showing my little steam engine on the Adafruit Google+ Show+Tell tonight. You can watch it streamed live on their ustream page. I won’t be running the engine live, due to the fact that my air compressor and my wifi don’t coexist in the same place, but I will be talking about the design. If you want to see it run, here’s a short video that I made:

    And here’s a stop-motion video showing how the scotch yoke works:

    You can also check out the photos on flickr.

    Related links:

    Comparing crank & slider and scotch yoke linkages at Wolfram Demonstrations.

    Scotch yoke entry at Wikipedia.

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  • Poisoning History

    detail of the PCB in question, in purple 'cuz I got them from @Laen.


    In ancient times, digital mariners would steer their charges by the light of heavenly vias.

    Sometimes, they would see figures in the vias, and give them names.

    Dateline — The Distant Future ™: An archaeologist with a flying car rediscovers this circuit board in the ruins of a subdivision of a New York City suburb in what used to be New Jersey. Assuming they can decipher the bizarre, refined glyphs that make up the Latin alphabet, what will they think? Did people in the 21st century really believe that vias were stars, or vice-versa? Is this proof of a previously undocumented (and quaint) belief system? Did these people really believe in primitive anthropomorphized electrons?

    More than likely none of these. Assuming that people in the future will have stopped the ego-inflated practice of infantilizing the past, this artifact will be on display in a museum with the caption “A classic example of 21st-century wise-assery.”

    This is how it looks in Eagle.

    PCBs made using Laen’s DorkBotPDX PCB Service.

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  • “Drinks in the club, Hennessy bona fide / Roll up my sleeves, cufflinks to the side.”*

    Adafruit iCufflinks. Holla back!

    Click thru for the photoset.

    *that’s not actually a rap lyric. I just made it up to suit the picture.

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  • The Machine That Eats Everything

    This is entertaining and bizarre. The music really sends it over the edge.

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