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Impressive and slightly scary coilgun build


No, this is not one of the sci-fi video game replica weapon props I keep posting about—it's a real, functioning homemade coil-gun by Jason, aka YouTube user Larsplatoon, aka Photobucket and user Saz43, who has been working on it for two years. It's billed as a "1.25kJ Coilgun," but I dunno how that figure was computed. If it is muzzle energy then projectiles from this weapon deliver more kinetic energy than a .45 handgun but less than an M16 rifle, which I frankly doubt. But judge for yourself by clicking the embedded player below to be taken directly to the test firings at 2:50, in which various housewares get shattered and punched full of holes. I'm guessing 1.25 kJ is the theoretical maximum energy that can be delivered by the capacitor bank, and that the real muzzle energy is significantly lower.

Still, an extremely impressive project in terms of technical achievement , aesthetics, and "marketing." It raises an interesting question about the point at which "backyard ballistics" type projects cross the line to violate the unwritten rule here at Make: Online about not covering weapons or defense-related projects. Don't get me wrong, I think this is awesome, but if Larsplatoon and/or other amateur electromagnetic cannon experimenters get much better at what they're doing I may have to start thinking twice about passing these along. Don't try this at home, kiddies! [via Hacked Gadgets]


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Playing with the Arduino-compatible Beagle Board Trainer

Beagle Board Trainer

The Beagle Board Trainer from Tin Can Tools is a nifty daughterboard for the Beagle Board, offering level shifters for the built-in outputs such as GPIO, I2C, and SPI. This enables you to talk to 3.3v and 5v devices (the Beagle Board works with 1.8v signaling). Tin Can Tools sent me a Trainer board to take out for a spin.

My favorite part of the Beagle Board Trainer is the built-in Arduino-compatible subsystem. It's got an ATMega328 loaded up with the Arduino bootloader, all of the standard Arduino pins exposed, and you can talk to it over the Beagle Board's second serial UART (/dev/ttyS1).

Setting up the Trainer and the Beagle Board
I soldered some female headers onto the Trainer so I could stuff wires and components in and play with them, then I assembled the Trainer as directed in the Embedded Linux Wiki. Once I had the Trainer and Beagle Board connected, I was ready to install my kernel and root file system.

Although I use a Mac for day-to-day work, I keep a Linux virtual machine handy for projects whose instructions assume (or require) access to a Linux system. I use VMware Fusion, but this should work equally well with Parallels or the free VirtualBox on Mac or Windows. It might be possible to do this without a virtual machine, but it does require you to format an SD card with the ext2, which is tricky on a non-Linux system.

I followed the instructions to create a bootable SD card. To connect my SD card to my Linux virtual machine, I unmounted it in Mac OS X and went back to VMware, where I selected Virtual Machine→USB→Connect Apple Internal Memory Card Reader. Once I did that, I was able to access my SD card from Linux as though it were connected to a real machine.

My Beagle Board wouldn't boot correctly until I followed the steps from another set of instructions on Setting up the boot args. Once I did this, everything worked OK.

Sending Arduino Sketches to the Beagle Board
Now that I had a working Beagle Board connected to the Trainer, I had to figure out how to load an Arduino sketch onto it. The tricky part was figuring out how to generate a .hex file from Arduino. The Arduino IDE normally generates this in the course of loading it to your Arduino board, but it doesn't leave the .hex file laying around.

I used Martin Oldfield's instructions and Makefile for using Arduino from the command line. I opened the Arduino Fade example in the Arduino IDE (File→Examples→1.Basics→Fade) and saved it to my Arduino directory. Because the GND pin on the Trainer is so far from the Arduino-compatible pins, I added a couple of lines to Fade's setup() routine, which makes pin 10 a ground pin:

pinMode(10, OUTPUT);
digitalWrite(10, LOW);

Next, I created a Makefile that looked like this and put it in the sketch directory (/Users/bjepson/Documents/Arduino/Fade on my computer). You may need to change the setting of ARDUINO_DIR, and you will need to change the last line that starts with include:

ARDUINO_DIR = /Applications/
TARGET       = Fade
MCU          = atmega328p
F_CPU        = 16000000
ARDUINO_PORT = /dev/cu.usb*
ARDUINO_LIBS = LiquidCrystal
include /Users/bjepson/src/arduino-mk-0.4/

Then I went into the Terminal, used cd to change to the sketch directory, and typed make. When I was done, there was a file called Fade.hex in the build-cli subdirectory. I powered down the Beagle Board, put the SD card back in my computer, and copied Fade.hex to the root of the root file system. I also copied the avrgal binary, which is a lightweight alternative to avrdude. I unmounted the SD card, plugged it back into the Beagle Board, and powered the Beagle Board up again. After it started up, I logged in as root, used cd to switch to the directory where I copied avrgal and Fade.hex, then ran this command as I pressed the reset button next to the ATMega328 (not the Beagle Board's reset button): ./avrgal Fade.hex. Here's the output I saw:

Uart port used                      : /dev/ttyS1
Autodetect for Fade.hex             : Intel Hex
Acquire SYNC with AVR               : Passed
Uploading and writing to flash      : Passed

When I was done, I connected an LED to pin 9 (the positive, longer lead) and to pin 10 (negative lead). The LED faded just like it should. Now I've got a low-power Linux system with an Arduino-compatible peripheral hardwired to it. There are a lot of possibilities with that combo.

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Announcing Science Hack Day SF!


Here's a message from Ariel Waldman, announcing the first US Science Hack Day, happening right in the heart of Silicon Valley! Makers can post their ideas to the wiki and hack with us when the day (Nov 13-14) comes. I'm helping to organize the event. Hope to see you there! -- Eri

We're super excited to kick-off the announcement of Science Hack Day SF!

What's a Hack Day?
A Hack Day is an event that brings together various types of geeks in the same physical space for a brief but intense period of collaboration, hacking, and creating awesome things. A hack is a quick solution to a problem - maybe not the most elegant solution, but often the cleverest (e.g. mashing up APIs, datasets and web interfaces from different sources in new and interesting ways). A Hack Day is usually 48 hours long and involves a sleepover ...although not much sleeping happens when everyone is either hacking or playing Werewolf. Some Hack Days have a specific focus. There have already been very successful Music Hack Days and Government Hack Days. It's time for a Hack Day focused on Science! The mission of Science Hack Day is to get excited and make things with science*!

Who is Science Hack Day for?
Imagine a Venn diagram showing the intersection of web geeks and science geeks ...that's a pretty big intersection. Science Hack Day is for anyone with an interest in bringing science and technology together (from dabbling with APIs/datasets/interface design to biotech experiments and prototyping near-space payloads). If you're a coder, designer, scientist, citizen scientist, hacker or just an enthusiastic person with good ideas, Science Hack Day is for you.

Give me the data already!

How do I register to attend?
This week, we're collaborating with scientists, technologists and designers that will help seed the event with example ideas and raw stuff to hack on. On October 1st, we'll open up the first wave of tickets (it's free to attend, but since we have a capacity of 100, we'll want to ask about your interest/intentions with our daught...err, I mean, event). Sign up using your email address here to receive an email once we open up the registration process.

There are of course a lot more details to be announced (sponsors, competition categories and prizes for best hacks, etc.), so stay tuned! Any questions, interested in sponsoring or want to get in touch with us about Science Hack Day? Send emails to

Lastly, I assembled an amazingly super awesome team (17 strong!) of science and technology people who are helping co-organize the event: Arfon Smith (Galaxy Zoo), myself - Ariel Waldman (, Amber Case (CyborgCamp), Ben Ward (Yahoo! Developer Network), David Harris (Symmetry Magazine), Ed Gutman (Twitter), Eri Gentry (BioCurious), Ian Fung (UserVoice), Jeremy Keith (Clearleft), Jessy Cowan-Sharp (UMD), Kirsten "Dr. Kiki" Sanford (This Week In Science), Kishore Hari (UCSF), Mathias Crawford (Institute For The Future), Matt Hancher (Google), Matt Wood (Amazon Web Services), Natalie Villalobos (Google), Tantek Çelik ( + Mozilla). You can follow all of us on Twitter here!

Get brainstorming!

--Ariel Waldman

(* just to be clear: you don't need to have experience with hacking on science-related things to attend - just an excitement for experimenting with it!)

Bio: Eri Gentry is a biotech entrepreneur, citizen science community organizer, and the co-founder of BioCurious, the first hackerspace for biotech, in the San Francisco Bay Area.

Check out our entire Science Archive on MAKE

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Repair on the playa



Our friend Kyle Wiens of iFixit made it out to the annual Burning Man arts festival this year, with the goal of checking out repair efforts on the playa. The harsh environment of Black Rock Desert becomes home to purportedly the most populated temporary city in the world for one week of every year. Repair is naturally integral to survival. Kyle shares his findings in a general post about repair on the playa and another more specifically about bike repair, bikes being the transport of choice for most attendees.

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Visual 6502


Visual 6502 is a javascript simulation of the venerable 6502 processor, that can run in your web browser. Impressive! [via boingboing]

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Math Monday: Human-scale string constructions

By George Hart for the Museum of Mathematics


A complete graph is what mathematicians call a collection of items in which every pair is connected. If the items are spaced evenly around a circle and the connections are shown as straight lines, the lines form an attractive pattern of concentric circles.


This is a complete graph with eleven vertices. We made it at Mathcamp 2010 using plastic surveyor's tape. There is a simple algorithm for constructing it in which people stand in a circle, and pass the roll from one to the next while counting aloud, wrapping it around their left wrist at the proper intervals.


A similar algorithm, executed by people standing in two straight lines, gives this large parabola. The construction steps for both of these figures can be seen in the additional photos here.

See all of George's Math Monday columns

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Teardown madness, MASSIVE take-apart roundup

Taking things apart is fascinating. Before you throw away another piece of electronic garbage, disassemble it and try to figure out how it works! There's still time to participate in the Technojunk Teardown Family Challenge (hint: more than just families can enter), take apart some junk, document it, win tools! Here's a roundup of our favorite teardowns.

Epic HP printer take-apart

iPod Touch 4th generation teardown

IFixit's sponsored blender teardown

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ChronoDot is now Open Source


Garrett Mace of Macetech has announced the company's first entry in the open source hardware realm, with the release of the ChronoDot RTC as an OSHW project.

Over the past few years, a lot of small electronics hardware businesses have been starting up. Many of the more successful businesses and projects have adopted "open-source" philosophy into some or all of their products. Open-source concepts have been in existence for a long's human nature to share information and explain how we made something. At the same time, there is what appears to be a conflicting desire to keep processes secret in fear of duplication.

...So our first open-source product is a pretty simple design, the ChronoDot RTC breakout board based on the Maxim D3231 temperature compensated realtime clock chip. Design files for Eagle are included on the product page, or at this link:

If you don't want to make your own, you can buy a ChronoDot from Macetech's store.


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GITD Iron Man cross-stitch

Reminder: Family Challenge -- Technojunk Teardown

Don't forget, we're closing in on our Technojunk Teardown contest. If you're participating, do send in your entries ASAP. If you haven't whipped out the drivers and gotten busy on a cast-off piece of technojunk yet, there's still time! Deadline is 11:59 p.m. PDT on September 24, 2010. There are some great prizes at stake (provided by Maker Shed), including this sweet Make: Electronics toolkit.

See the original Challenge post for full details.

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It's a ball of LEDs


Instructables saronpaz made this "so simple its embarrassing" ball of LEDs with a few coincells inside, with a neat effect!

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Your Comments


And we're back with our fourteenth installment of Your Comments. Here are our favorites from the past week, from Make: Online, our Facebook page, and Twitter.

Todd Harrison shared an, er, alternative to Kip Kay's Lily Pad Pool Warmers Weekend Project video:

My DIY redneck pool heater would be a lot less fuss.

There was quite a strong reaction to the video demonstration of free Climbing a 1700 foot antenna tower. Over on Facebook, Kenn Mileski summed up the reaction:

I had to stop watching when the climber said 'free climbing'. Every professional climber I know would be fired IMMEDIATELY if they violated the 100% tie-off rule. He should have been climbing with TWO fall arrest lanyards with at least one tied off at ALL TIMES.

Also on Facebook, Randolph Bean admits to working at a slightly longer time scale than that demonstrated in the video How fast can you take apart and put a Jeep back together?:

Wait...what? You have to put it back together?!?!?! I better get to work, so far I've only taken about 15 years....

Dave reiterated some basic safety tips to keep in mind when making a DIY ultraviolet laser from scrap aluminum:

Nyle made some good points about safety in the original article, but said only a little about laser light concerns.
UV lasers are dangerous, perhaps more so the IR, as the invisible beam is of higher energy. Wear some appropriate goggles when working with a TEA laser. At the very least, dark, UV blocking sunglasses!
Running the beam through a mason jar of fluorescent liquid is a wonderful way of visualizing its path, but there will be a strong, invisible reflection from the glass, where the beam enters. Beware!
And, one wonders if the high voltage had its way, since Nyle's article is almost three years old! Hopefully, he is still with us!

Simon appreciates a good set of Dual-reading calipers with Imperial/SI units on same dial:

Those would be very handy. Although after such a long time at not having something like that I find I can convert from metric into imperial reasonably well now (how many thou in a mm again?). I find I prefer the analogue ones. Sometimes I want to take a smidge off something when machining and don't bother using the scale on the lathe but I get a good feel for how much a smidge is by how far the needle on the calipers moves.
I have also dropped mine and had them skip but I was able to take them apart and reset them.

Logan, co-creator of the DIY Underwater Bubble Room, chimes in to answer the question everyone was wondering about it:

Hello Logan here, I am the co-creator of the bubble room (along with my brother Jordan).
The maker of the mustache wax is "Firehouse Mustache Wax" ( If you go to the last page in their galleries there is a picture and a paragraph about Jordan and Dan (Dan is the guy in the video).
I agree a 50 ft wide bubble room would be amazing... The biggest problem I can see (possibly even a bigger problem than obtaining a dome that big) is that a hemisphere 50 feet across, full of air, underwater would have 2,042,954 pounds of lift (yes 2 million). That's about 1,021 tons. I'm sure it could be done but the physics and material behind that structure would have to be very intense.
Also a tunnel to the surface would not work at all unless you had an air lock.

Commenter kinderdm shares some insider knowledge about vibrating conveyor belts:

My father works as an engineer for a company that produces vibrating conveyors (among other things) on an industrial scale. They have been doing such business for as long as I can remember, at least 25 years. As I understand it these systems are very useful in applications that involve small items, which could be lodged in the moving parts of a traditional conveyor. They are also useful in the food and pharmaceutical industries where lubricant contamination could be a concern. A vibrating conveyor can be made from a solid piece of metal so that the parts that contact the product require no lubrication. They also lend themselves well to sterilization as there is no where that contaminants can hide.

Salec had some sort of advice about how to make use of some of the parts being stored in the binder part storage post:

Yes, too often 555 pushes 4017 around, poor 4017 having no negative feedback on 555 whatsoever, which would be ... hey, now when I think about it, quite an intriguing idea, thank You!
Here, try this: let 555 (as astable) clock the 4017, then make jumper-selectable decoded output of 4017, over a resistor, change the frequency of 555. Tap audio from 555 output to some sounding device. See what sounds it can produce on a speaker when you change the selected 4017 output to another one.

Inspired by the Simple method for constructing a worm gear, Dean W. Armstrong had a few more tips on how to make them:

Cool! Another interesting way some telescope makers make worm gears: they apply partially-set JB weld to the outer rim of the worm wheel, then put a nylon rod in the goo and let it set. The JB weld doesn't stick very well to the nylon. I think I have read another way is to drive the nylon worm and worm wheel very carefully during the gooey phase and you get a perfect match between the two gears.

Brushyfork was having trouble putting together an Hydrogen-Oxygen Bottle Rocket:

"Seriously, this is almost literally killing me. I want nothing more in life than to launch this rocket. Please help me figure out what is wrong."

After the author stepped in and helped out with some advice about timing, they left an exciting comment:
"I've gotten it working!"

Like these comments? Be sure to sound off in the comments! You could be in next week's column.

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Make: Projects - Permanently stain PVC pipe any color you want


I love PVC pipe: It's weatherproof, cheap, commonly available, easy to work, and easy to join temporarily or permanently. Apart from a slightly icky environmental footprint, the only serious drawback of PVC pipe for non-plumbing projects is that it's ugly, owing largely to the fact that it's usually available only in white, off-white, gray, or (sometimes) black. PVC can be painted, sure, but getting a good finish requires careful surface preparation, and even then the paint tends to flake or wear off with time, weather, and/or handling.

But, as you'll know if you've ever tried to remove a purple primer stain, it is possible to indelibly colorize PVC pipe. I got curious about what was in purple primer, and a bit of digging revealed that it's just clear primer plus purple dye. I reasoned, then, that I ought to be able to make my own "purple primer" in whatever color I wanted by adding solvent dye to clear primer. Long story short: It works, and it works great. Details are here.


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Inexpensive tablet wall mount


Sometimes you have a real need to mount your tablet computer to a wall or other vertical surface. That's where common sense and good old fashioned ingenuity comes in. Seattle area foodie and avid DIY'er, Tumbleweed, shows us that you needn't spend exorbitant amounts of money on some specialized billet aluminum wall mounting kit. A $2.84 "Delux Plate Hanger Set" will do the trick. [via LifeHacker]

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PS3 Move controller teardown


Ever since it debuted I've wondered what made the PS3 Move controller tick. The folks over at iFixit have satisfied my curiosity with their latest teardown. Behold the highlights:

  • The PlayStation Move, unlike the Wii, can locate the motion controller in 3D space. The PlayStation Eye camera visually recognizes the X/Y position as well as the relative size of the glowing orb on the motion controller to pinpoint the controller's location.
  • The battery gets brownie points for being able to be disconnected from the Move without any soldering. Just unplug the connector and plug the new one in.
  • STM32F103VBT6 ARM-based 32-bit MCU with Flash, USB, CAN, seven 16-bit timers, two ADCs and nine communication interfaces.
  • The LEDs in the end of the motion controller are capable of 24-bit color resolution.
  • The trigger comes out as one unit, making it easy to replace.

Since we're on the subject of teardowns, there's still a few days left to gather up your crew and participate in our very own Family Challenge Technojunk Teardown.

PlayStation Move Teardown

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Fab Academy in Providence now accepting students

Fab Academy

James Rutter from AS220 wrote in to let us know that the next session of the Fab Academy at AS220 is accepting students for the 2010-2011 term:

The Fab Academy provides instruction and supervises investigation of mechanisms, applications, and implications of digital fabrication. The academy is a new distributed education platform built on the infrastructure of the international Fab Lab network and taught by MIT professor Neil Gershenfeld and a global roster of visiting faculty and local instructors.

Local costs are $218 per 2 week class ($3,500 October through June), and scholarships may be available. Classes are three times a week beginning in October at the Providence Fab Lab at AS220.

Fab Academy at AS220 Labs

For more information on the Fab Academy, check out Shawn Wallace's series:

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