Weekend Projects maker Max built experiment #21 from Charles Platt’s book Make: Electronics (a great primer for anyone looking to learn electronics or brush up on theories and essentials). This experiment formed the basis for the Game Show Buttons project from earlier this year, and Max does a wonderful job on his Google+ post of giving a simple explanation of this fairly complex circuit and highlighting the various components. This circuit is built using an OR logic gate, which as the name implies is true (on) if either input A or input B is true. The OR is one of seven common types of logic gates, the others being AND, NAND, NOR, XOR, XNOR, and NOT (or as most call it, an Inverter). If you build Game Show Buttons or any other Weekend Projects, be sure to send us an email with pictures and a story about your build.
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See all of the Weekend Projects posts Filed under: MAKE Projects, Weekend Projects         
 
 Vacuum metallization is a process for coating objects, most often engineering plastics, with an extremely thin (~0.1 μm) metallic coating. It’s done, essentially, by condensing vaporized metal fumes on the surface to be treated inside a vacuum chamber, and is a common means of “chrome plating” plastic parts used, for example, in toys.
I have been hacking on some cheap R/C cars, lately, and wanted to etch these metal films off of a few of the bits, A) to prevent it from shorting across exposed electrical connections and B) for aesthetic purposes. It looks gaudy, IMHO, and does not take paint very well. I knew that the usual strong acid and base suspects would remove it, and at first I was etching parts in disposable plastic cups containing about 12 oz of tapwater and 1/8 tsp Red Devil lye, which of course is sodium hydroxide. Hydrochloric (aka muriatic) acid will also do the trick. I am not especially intimidated by these substances, but many people don’t keep them around, for whatever reasons. And unless you’re in a hurry, there’s no reason to use them if something milder will serve. I got curious, and did a simple test with some household chemicals. I broke a metalized “roll cage” from an R/C truck into five pieces and soaked each in a different solution overnight. I used vinegar, an arbitrary mixture of vinegar and hydrogen peroxide (the strong hair-bleaching kind), straight hydrogen peroxide, diet coke, and an arbitrary mixture of diet coke and hydrogen peroxide. It was not a very scientific process, but vinegar seems to work well. Specifically, I used “extra strength” distilled white vinegar labelled as “9% acidity.” Hydrogen peroxide seems to have no useful effect. Diet coke works pretty well, but the carbonation causes bubbles that displace etchant and leave shiny spots on the surface. Your mileage may vary, depending on just how your parts were metalized (and with what metal), but if you have need of this process, vinegar may be a good place to start experimenting. Also, though I wanted to completely remove the metal films from my parts, it should be fairly straightforward to apply masking agents and etch decorative and/or functional patterns in them, if you should need or want to. Filed under: Chemistry, Laboratory, Toys and Games         
 
I love Dane Kouttron’s monster 3D printer! This project documents the re-purposing of a ‘rescued’ 1980′s IBM 7575 SCARA Robot Arm, into a functional 3D ABS printer. The project features some motor upgrades [listed earlier], documentation of encoder positioned motor control feedback theory, the interminglings of EMC2 [Linux CNC], heated workspace construction and a step by step overview of transitioning from 3D stl model to 3D g-coded structure. The huge reach of the 7575, allows for printing large objects, (roughly ~25″x12″x6.5″ maximum). Some of these prints are shown below.
Be sure to check out Dane’s build notes, which are almost absurdly detailed. [Thanks, Matt!] Filed under: 3D Printing, Robotics         
 
Achieving Balance By Laura Kiniry Photos by Rachel Fong Tired of walking to the supermarket from his dorm, 21-year-old MIT computer science and electrical engineering student Stephan Boyer decided he needed a quicker way to travel. "I wanted a personal transporter that could get me around campus but be as small and light and fast as possible," he says. Five months later, Boyer had Bullet, a self-balancing electric unicycle that reaches a top speed of 15 miles per hour and is the envy of his peers.  Boyer built Bullet with $1,000 and endless ingenuity. After teaching himself welding and some mechanical engineering, he got to work collecting materials: a basic fork to hold both a moped wheel and motor, welded-on pedals to provide foot support, and a top seat. "I didn't really plan out the [entire design], so the battery and electronics are held on with zip ties," he says. Bullet also features a kill switch for swift deactivation. He says the design could be built for $600.
For balance, Bullet employs an onboard computer and two sensors: a gyro and an accelerometer. The former measures Bullet's rotation speed and the latter determines its acceleration due to gravity. Using this data, the computer can detect the angle of the unicycle and prevent it from leaning too far forward or backward. "Because Bullet only has one wheel, you still have to balance side to side," says Boyer, who does this by twisting his hips to turn and occasionally flailing his arms for stabilization, in the same way a flying squirrel uses its tail. Riding it several miles daily, Boyer became somewhat of a pro at handling the vehicle, but he stresses that it takes both skill and patience. "My number one rule when riding Bullet is that things in the road are always bigger than they appear."
 
From the pages of MAKE Volume 31:  The maker movement is making science exciting again. Forget the lame baking soda “volcanoes” and the zillion-dollar supercolliders — just as punk rock took music back from the supergroups and big studios, “punk scientists” are making inexpensive new tools to conduct real experiments in garages, schools, and hackerspaces. In MAKE Volume 31, you’ll learn how to make DIY laboratory equipment (even a scanning electron microscope!), create high-voltage sparks from falling water, control a cockroach electronically, get started in biotech, and see how individuals and schools are networking their data for real scientific discoveries. Plus: Get started with multicopters or servo controllers, and build an automatic dog ball launcher, great-sounding speakers with flashing LEDs, a classic folding-wing Rocket Glider (a new MAKE kit), an iPad music desk, a levitating solar Mendocino Motor, and much more.
BUY OR SUBSCRIBE! Filed under: Bicycles, Made On Earth         
 
Alasdair Allan, author of iOS Sensor Apps with Arduino, is presenting an iOS Sensors and External Hardware Masterclass in London in October: This one day course will guide you through developing location aware applications for the iOS platforms that make use of the onboard sensors: the 3-axis accelerometer, the magnetometer, the gyroscope, the camera and the GPS. You’ll learn how to make use of these onboard sensors and combine them to build sophisticated location aware applications. You’ll also learn how to extend the reach of the on-board sensors by connecting your iOS device to external hardware. We’ll look at how to connect the Arduino microcontroller platform to your iOS device, and build simple applications to control the board and gather measurements from sensors connected to it, directly from iOS. This course will give you the background to build your own applications independently, using the hottest location-aware technology yet for any mobile platform.
For pricing, registration, and more information, see Sensor Workshops. Filed under: Announcements         
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