By Meara O'Reilly, projects intern

I've been working on winding coils and testing out a cool new electromagnetic guitar pickup for the upcoming issue of MAKE, so I thought I'd share a modification I did a while ago on the old piezoelectric pickup that was featured on the quick and easy Cigar Box Guitar in MAKE Volume 04.

Here's the piezo buzzer used for a pickup in MAKE's original Cigar Box Guitar, still encased in black plastic.

Piezoelectric transducer discs often come in protective plastic casings, but they're actually much more sensitive without them! I've spent many an hour with needlenose pliers cracking them open like steamed lobsters to get at the ceramic and metal underneath, and I've found the difference in amplification to be definitely worth it.

The original design had the plastic-encased piezo element (a piezo buzzer) inside the cigar box, and it worked fine, but I've learned that it works even better without the plastic case.

One of our old CBGs even had the piezo buzzer mounted directly under the strings, sort of propping them up into alignment with the fretboard, in order to show off the pickup. This was failing for two reasons: first, the point of contact was too broad, causing a buzzing sound as the strings hit the long, flat surface of the plastic, and second, because the piezo disc was oriented at the bottom of the plastic casing, it was protected from some of the most important vibrating bodies on the guitar -- the strings!

I decided to build something where a narrower contact point (or bridge) could directly conduct the vibration from the strings to the disc.

Here's my modified piezo pickup, naked, in direct contact with the bridge, and sounding great.

I cut a small block of balsa wood (about the width of the fretboard and long enough for the disc to rest comfortably upon) to prop up the whole setup. I placed placed the piezo on top of this balsa base, then cut a small piece of a wooden barbeque skewer we had lying around and placed that on top of the piezo as a bridge.

The strings, once wound on, will normally hold the bridge in place (in fact, many types of acoustic guitars have some sort of free-standing bridge like this), but for extra security, I cut both of the rounded ends off a popsicle stick and glued them flush with the balsa block to provide a sort of "baby gate" for the skewer, to keep it from rolling too much.

Voilà! The smaller contact point, applied directly to the piezo disc and held in place by the strings, conveys the string sound wonderfully.

What pickup modifications have you discovered?

My Make: Projects - Bottle cutting post has proven to be one of the most popular of the series. So here's a short follow-up revealing a simple trick I discovered for etching designs on glass bottles using the bottle's label as a built-in resist.

This week's Flashback, from the pages of MAKE Volume 15, shows how authors Jim Moir and Ken Lange devised a camera setup to auto-trigger photos of the critters who came to visit their backyards in the dead of night. Judging from the multitude of pictures they've gathered over the years, there is no shortage of wildlife variety in their neighborhood. Check it out to build your own and see what's lurking behind your house. You can also still pick up a back issue of Volume 15, the Music issue, over in the Maker Shed.

Caught in the Act
By Jim Moir and Ken Lange

Ever wonder what's getting into your garage at night, eating your cat food in the backyard, or coming by your tent when you're camping? Now you can find out. With a digital camera, flash, and triggering mechanism, you'll be able to see exactly which critters are prowling at 3 a.m.

Although there are some challenges to overcome, we've discovered that there are plenty of solutions to develop a remote wildlife photography system that meets your needs and budget. Film cameras were used in the past, but clearly digital cameras bring this hobby to a new level by eliminating the expense, time, and effort that comes with film.

MATERIALS
Digital camera We prefer the Kodak DC-290 and discuss its benefits in this article.
Infrared (IR) detector or motion sensor
Camera flash
Power supply

What Does It Take to Do This?
Our challenge was to choose a camera system that can stay awake for long periods (most shut down after a few minutes to conserve battery power) and to rig a method for sensing the animal and triggering the shutter remotely. We also needed a flash capable of illuminating an area large enough to capture pictures of what tripped the camera. Finally, we needed power reserves big enough to run the camera, the external flash, and the animal-sensing trigger mechanism for several days.

What Camera to Use?
We evaluated the 2 typical camera types -- point-and-shoot and SLR -- to capture our wildlife images. Both have advantages and disadvantages. Point-and-shoot cameras are inexpensive but need a lot of modifications to work. SLRs have more features but can be pricey.

We chose a third path and used the Kodak DC-290. This modestly priced camera was an excellent choice, with a respectable 3.3-megapixel picture and many programmable features not available in most point-and-shoot cameras. This enabled us to make the system work without extensive hacking, and at the same time kept the total system to a reasonable cost. While this camera is no longer in production, it is regularly available on eBay for $50 to $150 (depending on condition, accessories, and demand).

I thought I was really into coffee until I met John Edgar Park, host of Make: television, contributing writer to Make: Online, and author of several MAKE magazine articles. John takes his coffee seriously. Seriously. Case in point was when he devised and wrote a how-to for his Florence Siphon Brewing and Extraction Apparatus for MAKE Volume 17, our Lost Knowledge issue. This apparatus is sure to raise eyebrows (and spirits) next time you invite someone to your workshop for a cup of blessed joe. Check out the whole project in this week's Flashback, and pick up a back issue of MAKE 17 over in the Maker Shed.

Make your own mad-scientist coffee machine.
By J. Edgar Park II

Aboard the dirigible Aeroship Phaedrus, two men are seated at a table in the onboard Laboratory:

"Doctor Liepold, would you kindly prescribe something to lift my depressed spirits?"
"Why of course, Captain Heffernan. What is it that ails you?"
"My mind feels sluggish and there is still much work to be done before daylight. I am drawing up charts for the expedition."
"Ah, yes, I have just the thing. Sit a moment while I extract the invigorants from these wondrous beans."
"Very good, thank you. What is that strange device, Herr Doktor?"
"I call it the Florence Siphon. It is an arabica brewing and extraction apparatus. Allow me to demonstrate. First, I fill this boiling flask with a quantity of pure spring water. It is a vessel of my own devising that can withstand great heat and pressure. I heat the flask, which causes the water to vaporize, passing through this tube here, through a filter, and into the beaker to my left. Here, the water commingles with precisely roasted and ground fruit of Coffea arabica. I give the slurry a rapid stirring to fully saturate the grounds, then wait.
"As my boiling flask cools, a vacuum is created, causing the very atmosphere of the Earth to push the liquid through the filter, leaving the grounds and all unsavory particulate matter behind. Thus the liquid, now filled with essences, oils, solubles, flavors, and vital invigorants, is returned to the flask. Allow me to unstopper it and pour you a dose."
"Doctor! You have outdone yourself! I feel revitalized by this most miraculous potion."

The vacuum siphon coffee brewing method dates back to the 1840s. It produces some of the cleanest, smoothest-tasting coffee of any method. Commercial vacuum pots are available, but I wanted to heighten the drama of vacuum brewing by taking it into the realm of the mad scientist's lab. Thus the Florence Siphon was born!

After studying original patent drawings and existing devices, I identified these key features:
• Water is heated in a boiling flask that has a tube leading to a second vessel containing ground coffee.
• The tube must have a filter, to allow the water to flow through but not the grounds.
• The filter must be submerged during brewing, so as to maintain a seal with the boiling flask.
• The second vessel must be accessible for stirring the slurry.
• The boiling flask must be large enough to create a sufficient vacuum as it cools to "pull" the coffee back through.

One drawback to early vacuum brewers was the constant danger of exploding glass. Today, we have plenty of high-quality borosilicate glassware that's up to the task — it just happens to be found in the lab, not the kitchen.

Filtration was another challenge. I tinkered with a few options (including an unfortunate foray into shower heads) before arriving at an inverted thistle tube. This is a type of bulbed funnel that's easy to cover with filter cloth. (Thanks to Dr. Jim Callan from Avogadro's Lab Supply for this suggestion.)

I assembled my funnel, stopper, tubing, filter, and a beaker for the grounds. I filled my flask with preheated water (small burners can take a while to boil 500ml), poured 38g of medium-ground coffee into the beaker, donned my goggles, and lit the burner.

The water began to bubble quickly, and soon went straight up the glass tube and over to the grounds. After about a minute, the flask was nearly empty and I extinguished the flame. At this point, there was an abundance of expanded water vapor (steam) inside the flask, which prevented the water from returning.

I stirred up the slurry with a stick and then waited with great excitement. Would the siphon be able to draw the coffee back up? At just about the 2-minute mark, I saw the gorgeous brown liquid begin its ascent. This is due to the vacuum created by the cooling and contraction of water vapor in the boiling flask. It was tentative at first, but as the boiling flask continued to cool, the coffee started to move quickly up the tube, over and then back down to the flask below. Within another 20 seconds, the journey was complete: 420ml of coffee made it back, leaving 80ml of water behind with the grounds.

I removed the stopper and poured myself a cup. It was perfect! Smooth, bright, clear, and clean. Vacuum coffee is a step above a French press, and leagues above drip. Plus, when you brew with the Florence Siphon you get to don your lab coat and cackle maniacally. What more could you want from a cup of coffee?

Here's how to build your own Florence Siphon.

Every chemist (and arguably every scientist, and arguably everyone else in the world), whether amateur or professional, should have an elements collection. Theodore Gray has written eloquently about the hows and wherefores of collecting the chemical elements, so I won't belabor the point here other than to say: chemistry has been called the central science, and arguably, chemistry's greatest achievement has been the discovery of the chemical elements, the realization of the periodicity of their properties and its implications for atomic structure, and the isolation of each of those elements in its pure or "standard" state. Collecting the individual elements lets you participate in that incredible story in a way that no amount of book-learnin' ever will.

Photos by Maya Chavez-Akin.

Making ice cream with cryogens stronger than water ice is a fairly common chemistry demonstration stunt. The ideal way to do it is with liquid nitrogen, which is poured directly into the ice cream mixture, with stirring, and causes it to set up in about 10 minutes. Liquid nitrogen, however, can be rather difficult to get your hands on. Most major cities have a supplier that will sell it to you, but very often they have large minimum orders and/or require that you own an expensive dewar flask into which they may safely dispense the liquid nitrogen. At -196 C, liquid nitrogen is also fairly dangerous to handle.

Dry ice is a much more accessible cryogen; it's available at several major grocery stores in the Austin area, for instance, and I imagine the same is true in other parts of the United States. It sublimes at -78 C, and is thus vastly more effective at freezing stuff than water ice at 0 C. You can make ice cream, just as with liquid nitrogen, by adding dry ice directly to the ice cream mixture. However, because dry ice is frozen carbon dioxide, this procedure results in carbonated ice cream. Which can be quite delicious. But say you don't want carbonated ice cream?

This procedure borrows from a common technique in the organic chemistry laboratory for cooling reactions to sub-zero temperatures. Instead of using ice water to cool to 0 C, you make a bath of dry ice in some volatile solvent that will not freeze at dry ice's sublimation temperature of -78 C. Obviously, you can't use dry ice in water because the water will freeze solid. In the laboratory, acetone and isopropyl alcohol are common coolants. Acetone, however, can be dangerous if handled improperly, and isopropyl alcohol in sufficient quantities to make a large bath can be rather expensive.

I have discovered, however, that denatured ethanol, which is available in hardware stores everywhere, is reasonably priced and makes a good bath with dry ice. Denatured alcohol is also much safer to handle than acetone. Depending on the denaturant, it is also the least toxic of the various hardware-store solvents. In any case, done with reasonable care, this procedure involves no significant risk of contact between the ice cream itself and the coolant. And although denatured alcohol is quite flammable, the dry ice temperature of -78 C is well below its flash point at 13 C, which means that, once the bath is cool, there is no danger of the alcohol vapor igniting from a stray spark. To err on the safe side, however, you should be sure to work in a well-ventilated area.

By Kris Magri, engineering intern

How I designed Makey, Part III: The Ping sonar rangefinder and maiden voyage

As we return to our robot design saga, making Makey the Robot for MAKE, Volume 19 ...

The actual robot is still just a prototype with 2 wheels and motors and no sensors, electronics, or brains inside. The better body exists only in the computer. Maker Faire is looming. I've been tapped to give two "Make Your Own Robot" workshops, and I reckon that having a working robot would be a very good idea.

I'm trying to get the Arduino into the robot body. Suddenly I learn a profound lesson regarding computer-aided design. In real life, circuit boards cannot morph through walls into their desired resting place. In the computer, it happens all the time. With a simple motion of the mouse, the Arduino circuit board has glided into place, right through the aluminum robot body ... but in real life, it won't fit. There is no possible angle or tilt that will get the Arduino into the robot. Out come the Vise-Grips and hacksaw. I saw, bend, and twist off the offending aluminum tabs. This is reality-aided design.

The battery pack doesn't fit because it hits the nuts and bolts that hold the motors in. It fit just fine in the computer model, since I didn't bother including the nuts and bolts. I'm ready to toss the computer out the window.

I show up at the Make: Labs with my fail robot. Our crew has been working like demons for weeks getting ready for Maker Faire -- preparing demos, packing everything under the sun, buying materials -- the lab is a madhouse. Eric, myself, and Steven are practically tripping over each other. I'm frantic to get the Arduino into the body and get the sonar sensor mounted somehow. Eric suggests double-stick tape. I refuse. Tape and glue, I assert, are for people who don't know about bolts and rivets. Eric manages to cram the Arduino in sideways. It barely fits, actually, it doesn't quite fit, it sticks up a little. When I drill a mounting hole, 1/3 of the hole isn't there. But the bolt manages to hold.

At this point I only have a vague idea of what motor will be turning Makey's "eyes" or how to fit it inside. We zoom off to the local hobby shop and pay way too much for the smallest servomotor they have in stock.

Steven offers to take on the servomotor/sonar sensor mounting problem. He's making detailed measurements and calculations, trying to figure out how much space there is and where the servomotor will fit into this 3D space without hitting the electronics. He marks everything and explains his calculations to me. I can't follow them, but it sounds good and looks like it might just fit. I drill the holes, we put the servo in, then close up the robot. It fits! There is much rejoicing.

Read full story

Now it's time to build the Y-stage. This only takes about 30 minutes and goes together fairly easily. One thing to note, some of the parts are laser etched on the wrong side. Take a close look at the pictures and make sure everything is going together the proper way. Apparently this is only an issue with CupCake CNC machines from batches 6-9.

Let's start by assembling the build platform. My kit came with a few extra, which is a good thing since the one in the picture doesn't work! The build platforms need to have (3) holes in the top to accommodate the (3) screws that are on the Y-stage assembly. I guess they redesigned the Y-stage and forgot to change the build platform. Oops! However, I received (2) additional build platforms in the kit, and both of them have the (3) holes allowing them to sit flush with the Y-stage. Problem solved!

The first step is adding the bearing brackets to the middle panel. These screw on the bottom of the middle layer with the included M3 nuts and bolts.

One in each corner, and... Done! Easy.

The Mendocino Motor project appears in the Teachers' Pet Projects section in MAKE, Volume 20, page 79.

Here are some techniques to design parts for the motor:

First get familiar with the SketchUp interface. This is pretty easy; the software is rather intuitive. A good place to start is by making whole shapes with the rectangle and circle tools. Draw a shape, then use the Push/Pull tool to extrude it up or down. You can make a shape on the side of another shape, then pull it out or push it in. Make some shapes. Mouse over the tool icons and you should see the name of the tool in a popup.

You can also do some neat stuff with the Move tool. If you have a cube, draw a line at the midpoints (again, mouse over the lines of your design and watch for the popups). If you pull the line up with the Move tool. This will give you something that looks a lot like a roof of a house on the cube. If you pay attention to the color of the line while you are moving it, you'll see that it takes on the color of the blue axis if you are pulling straight up. This means that you are moving parallel to the Z or vertical axis.

I wrote a couple of weeks ago about the excitement surrounding Clifford Wolf's new freeware OpenSCAD program. OpenSCAD uses a cool keep-it-super-simple approach to 3D modeling, eliminating the resource-hungry what-you-see-is-what-you-get (WYSIWYG) editing environment favored by most 3D modeling packages, and replacing it with a text-based scripting environment in which models are programmed, instead of sculpted. Basically, you write a script describing your model's shape and then compile it to produce the actual model, which is then rendered onscreen and can be exported to STL format for 3D printing or other purposes.

OpenSCAD has two powerful features to facilitate this programming processes. The first is support for so-called "constructive solid geometry" (CSG) modeling, in which complex forms are built up as intersections, unions, and differences of simple primary shapes like boxes, cylinders, cones, and ellipsoids. If you've ever used the ray-tracing program POV-Ray before, this idea will be familiar to you.

The second, less-well-publicized (but perhaps equally powerful) feature of OpenSCAD is "DXF extrusion," in which OpenSCAD will import a 2D drawing in AutoCAD's popular drawing exchange format (DXF) and "extrude" it into the third dimension. OpenSCAD has support for linear extrusion, in which the resulting part has straight vertical sides, and also rotating extrusion, which results in a part with helical sides. Since a large number of models for rapid prototyping are simple extruded profiles, I expect this feature to see a lot of use.

In this tutorial, I'm going to show you how to use OpenSCAD to produce a simple 3D model by extruding a part profile produced in normal drawing software. I use Adobe Illustrator CS3 because I have access to it and am familiar with its interface, but the popular freeware drawing program InkScape will read and write DXF files natively, and there's no reason why it couldn't serve just as well if you prefer it. There are a number of other free and low-cost programs that will export DXF files. OpenSCAD's developer mentions QCAD, which is available from its developer RibbonSoft for €24.

The part I'm making is one of 12 solid pentomino puzzle pieces based on the animals of the Chinese zodiac--in this case, the rabbit or "Z" pentomino. The designs are based on those of Japanese schoolteacher Sabu Oguro as published on p. 40 of Jerry Slocum and Jack Botermans' 1986 book Puzzles Old & New: How to Make and Solve Them, an image of which is reproduced at the top of this article. My original DXF files and the extruded 3D STL files are freely available for download at Thingiverse. This morning at 10 AM PST, Becky Stern will be streaming live video of her MakerBot CupCake CNC machine printing parts from this set, and she and I will be on-hand to chat about the printing process and the models themselves. Becky printed and photographed all the real-world models shown in this article.

First up, assembling the pulleys. If you purchased a kit, it includes a set of 3D-printed pulleys. This makes the pulleys really easy to assemble. However, there are a few tips and tricks that I'll cover.

First, make sure there are no extra bits of plastic in the pulley opening. If there are, carefully scrape them off with a hobby knife. Next, use one of the screws from the hardware burrito, along with a nut, to help push the bearing into the pulley. Screw the nut onto the bolt about 1/4" and then press the bolt head firmly until the bearing is completely seated. It's a snug fit, but you should be able to press it in fairly easily.

That's it! All the pulleys are assembled. If you are making your own pulleys from laser cut parts, check out this guide. Now it's time to apply a finish to your enclosure.

This tutorial shows how to take apart a spent zinc-carbon dry cell of the common household type. Besides making for an interesting object lesson in electrochemistry, taking apart a spent D-cell, for instance, allows you to salvage many materials which can be of use to amateur chemists--materials which would otherwise probably end up in a landfill. Separated from their reactive components, the leftover parts of the battery can be safely added to most municipal recycling streams.

A zinc carbon cell (Wikipedia) contains manganese dioxide, which, among other things, is useful as a catalyst in the production of oxygen gas from hydrogen peroxide. It also contains metallic zinc, which can be used, for instance, as a reagent in the production of hydrogen gas from strong acid. Finally, it contains a carbon or graphite rod which can be used as an electrode in any of a number of electrochemical experiments, such as the electrolysis of water and the construction of an arc light or arc furnace.

Note that the battery in this tutorial is a zinc-carbon dry cell. This tutorial does not cover the dismantling of an alkaline-type cell. Alkaline cells are of slightly different internal construction and contain the strong base potassium hydroxide as an electrolyte, which is rather more dangerous to handle than the ammonium chloride/zinc chloride mixture used in zinc carbon cells. Zinc-carbon cells are commonly labelled "general purpose" or "heavy duty," and will not have the word "alkaline" on the case.

Tools

• Small flat blade screwdriver
• Hobby knife
• Scissors
• Hammer
• Mortar and pestle
• Stainless steel or plastic strainer to fit coffee filter
• Stainless steel or plastic tray to work in

Materials

• Spent zinc-carbon or zinc-chloride D cell
• Wax paper
• Coffee filter

By Meara O'Reilly, projects intern

I've been tinkering with the electronics on various cigar box guitars for a while, but I'd never had the chance to build one from the ground up. So when MAKE editor-in-chief Mark Frauenfelder wrote up a new how-to for an acoustic version of the guitar for the upcoming issue (MAKE, Volume 21, "Traditional Cigar Box Guitar"), I jumped on the chance to test-build it.

Mark Frauenfelder's new acoustic cigar box guitar in MAKE Volume 21, coming in January.

As always here in the Make: Labs, it can be quite an adventure trying to sniff out all the possible interpretations of instructions while at the same time learning new skills, and this guitar build was no exception! I made two orientation-related mistakes based on an early manuscript and had quite a time trying to finish the build. In retrospect, the misunderstandings seem silly, but once made it's really easy for mistakes like these to compound -- due to structural weakness, later on my guitar neck snapped, twice! -- so I thought I'd write about them here, even just as an ode to those mistakes you think you'd never make, but somehow end up making anyway:

I planned on writing an entry about burning bootloaders and updating the firmware, but I just realized my kit comes ready to go! Yay! This is a major advantage to purchasing the Generation 3 Electronics kit. If you're making you own boards, be sure to check out these detailed instructions on burning bootloaders and updating firmware before going any further.

Here's the description of the Generation 3 Electronics kit [Mostly Assembled]:

This is a kit of mostly assembled electronics. All of the hard stuff is taken care of for you, and the only soldering that remains is the opto endstops which are very simple (only through hole components, no SMT). The stepper drivers, extruder controller, and motherboard all come fully assembled and ready to use. The extruder controller and motherboard have been pre-programmed with the MakerBot firmware and Arduino bootloader.

I know, I know, it's been a while since my last entry, and I apologize. The truth is, I was a bit under the weather last week, and my CupCake CNC kit had to sit and wait patiently for me to recover. The good news is, I'm feeling much better now and am super motivated to start printing parts! The next entry will be packed with CupCake building goodness. Promise!

Next up, making the pulleys and enclosure. As you can see, I chose a butchers wax finish. It's nontoxic, and nonflammable, which makes documenting it in my studio a lot easier. Also, it preserves the beauty of the wood, including the laser burns! Besides, if I don't like it, I can always cut out a new enclosure.

Ask questions! Do you want to see a better picture of a particular part, a different camera angle, a video perhaps? Maybe you have a suggestion for a cool mod or hack? Let me know in the comments. I'll try to answer them as best as I can. Thanks!

Build history:

• Part 1: Introduction & background
• Part 2: Unboxing
• Part 3: Electronics
• Part 4: Update & burning the bootloaders
• Part 5: Pulley & enclosure finishing
• Part 6: Building the enclosure
• Part 7: Building the Y-stage and adjusting the Z-stage
• Part 8: Building the X stage
• Part 9: Installing the X & Y stages
• Part 10: Installing the endstops & electronics
• Part 11: Building the plastruder & testing
• Part 12: Installing the electronics
• Part 13: Software installation & tuning
• Part 14: First print

Last week I wrote about how to construct a simple sheet metal "bridge," which, in combination with an ice cube bucket and an olive jar, makes an effective pneumatic trough for collecting gas samples over water. This week I'm going to show you how to use this apparatus to generate and collect pure oxygen, and how to use that oxygen to observe the brilliant blue flame of sulfur oxidation.

CAUTION

As a general rule, flammable greases like petroleum jelly should not be exposed to pure oxygen. There is no appreciable danger in this experiment, which involves only a small volume of oxygen at atmospheric pressure in a container with a free lid, but if you are working with larger volumes of oxygen, oxygen under higher pressure (as in a cylinder), or (most emphatically) liquid oxygen, do not use grease or other readily oxidizable materials in constructing apparatus.

Tools:

• Pneumatic trough apparatus from part I
• Small piece of plate glass (I used the mirror from a makeup compact)
• Lighter
• Twisted wire sample loop
• 250 mL Erlenmeyer flask (I got mine from The Maker Shed)
• #7 two-hole rubber stopper to fit Erlenmeyer (mine came from this assortment)
• Two 80 mm lengths of 5 mm glass tubing to fit stopper (such as this)
• Approximately 18" length of 5/16" OD x 3/16" ID PVC tubing to fit glass tubing (common hardware store item)

Materials:

• Water to fill bucket
• Elemental sulfur powder (also called "Flowers of Sulfur," available at some drugstores and here.)
• 3% hydrogen peroxide (common drugstore item)
• Manganese dioxide (can be recovered from an alkaline dry-cell battery or purchased here)
• Petroleum jelly (drugstore)

By Steven Lemos, engineering intern

Making the Hydrogen-Oxygen Bottle Rocket (that Adam Savage is posing with on the cover of the new MAKE, Volume 20) was a pretty basic endeavor, with the exception of the circuit. The original schematic diagram had a flaw in it, but only after we breadboarded the circuit -- twice -- did we catch it.

I guess that's the reason we MAKE interns build the projects that run in the magazine, so it's us who bang our heads against the table and not you. I will kindly take that cookie now.

The experience showed me that, sure, when working with electronics it's easy to misplace a component or wire, or completely miss something, which I already knew, but it's just as easy to have a diagram be the culprit. So a word to the wise (a word I'm sure all the experienced hobbyists have already discovered for themselves): if you take care when putting together these tedious circuits it will pay off, for if you can trust in your work, then you'll know the culprit lies in the plans, and you won't spend hours chasing that metaphorical wild goose.

Twice we breadboarded this bad boy before discovering an error in the schematic -- so you won''t have to.

But on to the actual launch. :) We had talked to the local electronics store owner, who at the time was making his own hydrogen using a more sophisticated apparatus, and who was interested in what we were doing with ours. So he came to watch, and brought along his professional pyrotechnician friend, who showed us how to make fuses with 12V and tiny resistors (basically the resistors pass so much current that the wire heats up and can act as a fuse to light stuff -- voilà, cheap fuses).

Our beautiful 2-stage HHO rocket ready for test launching -- before being crippled by a crash.

The first launch was a success, with the two stages going off rather quickly in succession, so we dialed in a little more delay time in the circuit before the stage 2 ignition. This was good and bad. We got more height out of the rocket on our second launch, but on its return it landed electronics side down. This resulted in our circuit behaving oddly.

So, not ready yet to call it a day, we began firing off only one stage at a time, adjusting the proportions of HHO (hydrogen and oxygen gases), water, and air, and testing the makeshift fuses, which worked fine for a single stage, but due to the time they take to ignite (3sec@12V) might not work for 2 stages.

We probably launched 12 times that day, attracting passersby. Good weather, new friends (who like blowing stuff up), and multiple launches. All in all, a good day. Houston, we have liftoff.

• Related: MAKE, Volume 20: "For Kids of All Ages"

Although it sounds like some kind of euphemism from Brave New World, a "pneumatic trough" is actually a very handy piece of classic chemistry lab kit. Besides providing a convenient means to collect samples of pure gases for various experiments, a pneumatic trough with a graduated container allows the easy volumetric measurement of reaction yields for gas-producing reactions.

If that all sounds too complicated, don't sweat. What I'm going to show in this tutorial is simply how to build a simple piece of apparatus that allows you to collect pure gas samples over water. You can collect carbon dioxide, oxygen, hydrogen--almost any gas you can generate and direct down a hose.

It seems like a simple enough bit of equipment: all you need is an upside down container suspended in a bucket of water. Finding a convenient way to set that up, however, is tougher than it sounds. The pneumatic trough presented here, which uses a sheet metal "bridge" to secure the glass column, is by far the most painless and economical way to make it work that I have found. The basic idea is derived from illustrations in Robert Brent's 1960 Golden Book of Chemistry Experiments (from which the title diagram is taken), but the addition of an aperture shaped to accept the threads of a glass jar is of my own devising.

Let's get started with the CupCake electronics assembly. I ordered the deluxe kit from batch #8, so most of the electronics were already assembled. Yay! Not that soldering isn't fun, but I'm happy to skip the soldering for this build and get to printing faster!

The stepper boards:

Not much to do here since the board is already soldered together. However, you do have to add the insulation-displacement connector (IDC) to the ribbon cables, and perform a simple test.

All you have to do is insert the ribbon cable into the plastic IDC connector and squeeze it closed. You might want to use some pliers to help snap the top down.

Take notice of the arrow on the connector. The brown wire is the index wire, and it should be directly above that arrow on both ends of the cable.

Rinse and repeat. You need to make three cables, each with an IDC connector on the end.

This kit has everything you need to build a MakerBot CNC and get started in DIY digital fabrication. Not only have we included all of the parts you need to build a CupCake CNC, but we've also included all the tools that you'll need to put it together and have the build go smoothly.

What exactly is included in the $950 deluxe kit?

• The laser-cut parts to assemble a CupCake CNC machine.
• 3 x NEMA 17 motors to drive your machine
• The nuts, bolts, and various hardware to assemble it.
• The belts and pulleys for it to move things around.
• All the bearings to make your machine nice and smooth.
• The highest quality precision ground shafts for the X and Y axes we could find.
• Pre-assembled 3rd generation electronics to drive it better, faster, and stronger.
• Magnetized, detachable build platform to make removing your finished prints easier.
• Pinch-wheel Plastruder to make things in plastic.
• 1lb of natural ABS to get you started printing in 3D.
• USB2TTL cable to talk to it
• cat5e cables to wire things up
• Standard ATX power supply
• Tools kit with all the hex keys, wrenches, and other bits you need to construct it.
• Full 5lbs of ABS plastic so you can print your heart out (in addition to the 1lb of ABS)
• Extra acrylic build surface, and a spare build platform
• SD card to buffer your prints

You can also save some money by purchasing the Basic CupCake CNC Kit for $750. Check out the link for more information about what is, and isn't, included in the basic kit. Then again, you could always build your own from scratch since it's totally open source.

Let the unboxing begin:

The first thing I found was a nice letter from the MakerBot team and a couple of postcards. I'm going to keep these filed away in a safe place. Maybe one day I'll be on the Antiques Roadshow and the host will let out a delighted *gasp* when I whip out my original, signed MakerBot Industries letter. Hey, you never know?!

Usually I write about ham radio. But looking at communication devices of the future from the past, I thought it would be fun to have a Star Trek: The Original Series Bluetooth communicator for a cellphone. I worked with Dave Clausen to hack one together from a toy Star Trek communicator, a Bluetooth module, and a microcontroller. Following are the directions and program to make your own. And of course a video to show how the Star Trek Bluetooth Communicator works.

And if you really want to geek it up, the Star Trek Bluetooth Communicator can also be used with the Yaesu VX-8R ham radio. It also makes an awesome gift. Read on for the full tutorial.

Oh wow, it's the CupCake CNC kit from MakerBot Industries! I'd ordered it weeks earlier and had completely forgotten about it. (The truth is out: I have an atrocious memory, sad but true.)

And so the adventure begins! I'm going to document my "out of box experience" with a MakerBot. How many posts will the series be? I'm not sure since I've never built one. How often will I post about the build? Again, not sure, but I'll try to do at least one a week, maybe more, it all depends on how much free time I have between all my other maker-ly projects.

A little background: My CNC experiences

I've been tinkering with CNC for about 10 years, and consider myself an enthusiast, not an expert. I do own a few CNC mills, routers, and lathes. I have retrofitted old mills, and even build one from scratch. Pictured above is my mobile CNC machine, dubbed the "MobileC." I stuffed all the components into a mobile tool cart so I could bring it to hackerspaces, workshops, and events, all in the hopes of helping out fellow makers.

By Kris Magri, engineering intern

How I designed Makey, Part II: Creating the "stretchy" robot body in Inventor

When designing Makey the Robot for MAKE, Volume 19, I ran into a problem that plagues all kinds of designers -- how to continually redesign a body to accommodate changes in whatever's crammed inside it?

Once I'd sketched out Makey's configuration and modeled the major parts in Autodesk Inventor 3D modeling software, I really got into some of Inventor's awesome features. Inventor has three basic design types you work with: sketches, parts, and assemblies. Up to this point I had designed each individual component, including Makey's robot body, as a part, as shown in Figure A.

Fig. A: Makey's sheet metal body, near-final version, shown as a single part in Autodesk Inventor. Because I designed it as a component of an assembly, all the mounting holes and dropouts are perfectly aligned to internal robot components; if I move the components, Inventor automatically moves the holes.

Once I had these parts modeled, I placed them together into an assembly, as in Figure B. Then, I attempted to stretch the robot body as needed by making that part "Adaptive" inside the assembly. (That's what Inventor calls "stretchy" parts, and it's a powerful feature.)

Fig. B: Makey's body shown as part of an assembly in Inventor, constrained to the edges of the motors (at bottom, in blue). If I move the motors, the body automatically stretches to accommodate the new motor positions. Similarly, I constrained the battery boxes (at top, in tan) to the body, so wherever the body stretches, the battery boxes follow automatically. Nice!

Also, I cut holes into the body where I needed them for mounting the motors. This was the wrong approach! It seemed to work, but when I looked at the robot body as a part, outside of the assembly, the holes I had made weren't shown. They had simply vanished.

The reason for this is that Inventor can't know ahead of time how you're going to use a part. You could design one part that could be used in multiple assemblies, so if you alter the base part in any way inside one particular assembly, the alteration exists only in the assembly, but the base part is unchanged. Thus, my changes didn't "take hold."

The key was to create the robot body from inside the assembly. You can actually be inside an assembly and make a brand-new part. To do this, in the Assembly Panel area, instead of selecting Place Component, choose Create Component.

I ended up first creating what I called a "base plate," which existed solely to help me anchor all the parts, including the robot body. It would not be a part I would actually fabricate. I then placed the base plate, the motors, the Arduino, and the batteries into an assembly, using Place Component, and assembled it all by anchoring everything to the base plate (using constraints). This was pretty much what I had been doing before.

Now, still inside the assembly, I created a new part, via Create Component, which would become the robot body. I selected the material type Sheet Metal.ipt, since it's a sheet metal part, and created each bend and flange step by step, inside the assembly. This robot body now "belonged" to the assembly, and was adaptive inside the assembly. Any editing of it, from that point on, was always initiated from within the assembly.

Instead of making the body a specific width, I just made everything extra large with no dimensions. Once the body was formed, I finished editing, and now I was back inside the assembly with my new robot body. I then constrained the side of the body to an existing "edge" from another part, for instance, the sides of the motors (Figure B). When the constraint went into effect, the sides of the body "snapped" into place next to the motors. To make holes, I projected the motor mount holes onto the robot body, again edited the robot body part (from within the assembly), cut holes there, and then the holes "stayed put," so to speak.

Success at last -- I had modeled a fully adaptive robot body that I could easily modify to accommodate all the robot components I would be cramming inside it.

Next up: The battle to fit the brains inside.

More: How I designed Makey the robot, Part I: The first design

By Kris Magri, engineering intern

Part I: The First Design

This summer I was given a once-in-a-lifetime opportunity to make a robot for the pages of MAKE Magazine (Volume 19, "My Robot, Makey"). As an intern, I had the inside scoop that an upcoming issue would focus on robotics. I talked with one of the editors, Goli Mohammadi, about including a step-by-step article showing people how to make their own autonomous robot from scratch, using an Arduino microcontroller. She took the idea to the rest of the crew, and they gave me a chance, asking for a draft article about the robot. I went into hyper-drive that weekend, designing and building a robot prototype in 44 hours over three days. This is a behind-the-scenes look at designing Makey.

The first thing I did was sketch ideas on paper. I based Makey on WALL-E, the little yellow robot hero from the movies. I quickly noticed that WALL-E's eyes are huge in contrast to his body. I knew the dimensions of the Parallax Ping sensor, which I planned to use for Makey's 'eyes,' so I realized I'd need to keep Makey's body as small as possible, to make the eyes look as big as possible.

I used Autodesk Inventor to design Makey. I can't say enough good things about this software. I've been using PCs for a good long while, and compared to big Unix workstations, I've never been impressed with what PCs can do for you. Inventor changed that. Inventor is the single best reason to own a PC, IMHO. I learned Inventor at school as part of my engineering curriculum, and this software is the "missing link" that has finally allowed me to design robots like I want to. Makey is the fifth robot I've built from scratch, and the first one I've designed on the computer, and the difference is like night and day.

Read full story

Sometimes you want to tell a story that takes a while to unfold. One of the beauties of digital photography is that you are not limited by how many shots are on the roll of film, now you can shoot until your camera's card is full. With the high capacity cards available now, you can shoot a very large amount of high resolution photos and barely fill your card.

In this project, we'll use Windows Movie Maker, which comes bundled with the operating system on many computers. If you have a Mac or Ubuntu machine, keep looking. iMovie surely has a process similar to this, and I haven't found a good way to work with movies on Ubuntu. Add your thoughts in the comments if you know of good software for other other platforms. All the windows machines in my classroom run on XP, I have heard that Moviemaker is a bit harder to find in Vista.

Making movies and sharing them online is a great way for students to sum up what they have learned from doing a project. By using the video description, students have a place to park a written explanation of what the project helped them learn and what the photos depict. They can write the text in any word processor and then add it to the video description when it is uploaded. If they need to alter it later, they can just edit the notes by logging in and making the changes.

They could be from The Necronomicon, Unaussprechlichen Kulten, or simply Poe's "quaint and curious volume," but everybody needs at least a few tattered leaves of ancient mind-blasting arcanum lying around to impress guests. Especially around Halloween.

This tutorial presents an easy method for producing weathered "antiqued" paper with burned edges. The trick of soaking white paper in coffee or tea to give it an old, yellowed look is very familiar, but the process for selectively burning the edges of the paper is something I discovered on my own. A simple and safe chemical treatment is used to selectively char the page, only where it has been applied, upon mild heat treatment.

I had two circuit boards nagging me to be etched this morning. Without a photo developing tray, it seemed some modifications in technique were in order. Into the recycling bin I went, looking for a smallish, wide-mouthed glass jar. Yesterday's sandwich polished off a tasty mango chutney, and the jar was just about right. A little bit of cleaning, and it was ready for business.

The leftover etchant from yesterday's vinyl PCB resist adventure was in a plastic bottle and still had some potency. The tea water was hot on the stove, so it was ready to provide some double-boiler action. I poured some hot water into a steel pan, put the ferric chloride into the jar in the pan, and dropped in the first board.

With a jar, you can tighten the lid and do more vigorous agitation than in a tray. Between the shaking and the heat, the process is quite a bit faster than when using a room temp bath and a pan. I forgot to check the time, but it was definitely quicker than yesterday. After the first of today's boards was cleared, I dropped in the second at 10 minutes to 11. This one I agitated even more than the first one, and it was easily done by 11. When it was clear, I rinsed off the boards and headed to the soldering iron.

After wiping down the boards with acetone to remove the adhesive from the vinyl sticker, I tinned the traces to get them ready for the chip, which will be soldered onto the PCB SMD-style.

This technique would be a lot simpler and safer to use with students in your maker classroom than agitating in open trays. Since the chemicals are sealed away inside the jar, there will be much less of a chance of spillage or splashing. Check out the PCB etching article in MAKE, Volume 02 for more ideas and techniques.

This is a simple kludge, really, but it's worked out remarkably well, considering I knocked it together in about 40 minutes 5 years ago and it's seen almost monthly use since then. What I started with was a pile of junk grill and smoker components, most of which came from a Brinkmann "Gourmet" smoker (as shown below) that my mother once accidentally set on fire. Lots of electric smokers have this three-part lid/body/base construction, however, and the exact make and model are not important.

This project began when I read the following entry [#274] in Volume 1 of Popular Mechanic's 1913 The Boy Mechanic:

The round lead weight for shot-putting or hammer throwing can be cast in a hollow cardboard or pressed-paper ball, sold in department and toy stores for 10 cents. Cut a 1/2-in. hole in the ball as shown in Fig. 1 and place it with the hole up in damp sand and press or tamp the sand lightly around the ball as shown in the section, Fig. 2. Cover over about 1 in. deep. A wood plug inserted in the hole will prevent any sand falling inside. When the sand is tamped in and the plug removed, it leaves a gate for the metal. Pour melted lead into the gate until it is full, then, when cool, shake it out from the sand and remove the charred paper. A file can be used to remove any rough places. The dry paper ball prevents any sputtering of the hot lead.

This idea of a hollow card or paper form buried in plain sand as a sacrificial mold for poured metal parts interested me. As the internet papercraft explosion has taught us, paper is really not a bad medium for 3D design, especially for the cost. Software like Pepakura Designer will convert any 3D digital model into a papercraft one that can be printed out, cut out, folded up, and glued or taped together to make a reasonably accurate real-world replica of the original. What if, instead of using the paper as a positive representation, one were to use it simply as a negative space--a volume, supported by dry sand, that would survive just long enough to impart its form to molten metal poured inside?

As a first experiment, I designed a paper template for the pieces of a classic put-together puzzle often called "The Four Piece Pyramid." The challenge is to use the four identical pieces to form a symmetrical three-sided pyramid. I chose this prototype form, first, because I think the puzzle is elegant; second, because all four pieces are identical so only one template design is required; and third, because the pieces are fairly simple, geometrically, and thus so are the templates.

Tools

• Computer with printer
• Scissors or an art knife
• Steel or aluminum bowl
• Safety gear (see below)
• Suitable heat source
• Melting pot
• Tongs or pliers for handing melting pot
• Squirt bottle with water
• Hacksaw frame with coarse blade

• 120 cm³ (1/2 cup) metal to melt (see below)
• Play sand (or table salt)
• The heaviest card stock you can get through your printer
• Printer ink
• Scotch tape

By Kris Magri, engineering intern

One of my favorite tools here at Make: Labs is the plastic bender. The coolest thing about it is using the variac, a giant heavy thing that truly adds some "mad science" cred to any workshop. You plug it in and crank the ginormous dial to vary the amount of AC voltage going through the heating element. How fun is that?

I followed the instructions in MAKE, Volume 10 (Project: Plastic Fantastic Desk Set), and made this spiffy tool holder for the lab.