Shiftycow.net

Classroom Wind Turbine Model

Michael — Sat, 07 Apr 2012 07:12:50 +0000

The class I’m working with for my GK-12 fellowship was studying energy last semester. [Paulo] (partner teacher) and I have put together several labs that teach students about energy and power, but wanted something fun to do with renewable energy. I made some lab models a couple weeks ago that were small solar hot water heaters, but they only just survived a day of use by ~120 students. As my girlfriend and others have pointed out, I put a lot of effort into lab aids only to use them once or have them destroyed. So for this lab, I decided to put together a much sturdier model that was designed to take abuse and could survive long enough to be donated to the STEM Outreach Center at NMSU where other K-12 teachers could check it out to use in their classrooms.

The final result was a windmill model. Paulo had done a wind turbine lab in the past where the students built turbines and used them to lift weights, but he wanted a more direct way of showing how turbines generate power.

The thing that sets this model apart from those available from kit manufacturers is that it uses a ~~permanent magnet alternator~~ stepper motor instead of a DC hobby motor. I liked the idea of using an AC generator that worked at the native speed of the turbines because it felt more “real” – no cheap pulleys or exposed gears or DC motors that only “simulate” how a big wind generator works. The blades are small (~30cm diameter), so there’s no way they could turn a long gear train, but I still wanted a scale model of a “real” turbine. I would totally have gone with a double-fed inductive generator just like the big boys, but I had neither the time nor EE expertise to make such a thing

It took a few iterations to get a nicely working generator, so check out the build process below and try to avoid my mistakes

–
Design Goals:
-Durability
-Interchangeable blades
-Able to generate enough power to light an LED with a box fan
-Teacher usable and serviceable

Durability and usability go without saying. An LED requires less power than incandescent lamps, so that was an obvious choice. Something else I wanted was to be able to change the turbine blades easily. Paulo had made a bunch of turbine “blanks” out of wooden spools and dowels for labs in the past. We thought it would be cool if the students could build their blades onto these blanks and then have a competition at the end of class to see who’s were the most effective.

First prototype:

The initial schedule was tight (2 weeks!), so I tossed something together using a 9V hobby motor:

This prototype looked cool, but it didn’t work at all. The blades spun the motor alright, but nowhere near the 10,000 RPM that would have been needed to get useful power out of the thing. The one thing that did work well was the drive shaft:

The aluminum drive shaft is made in two pieces. The “core” matches the ID of the spool on one end and is 0.25″ on the other end to fit through a bearing at couple to the motor. The second piece is a movable taper that transfers torque from the wooden spool to the shaft. The tapered piece is movable to accommodate different sized spools.

Second Prototype (Permanent magnet alternator)

After failing to get useful energy out of a DC motor, I went to the other extreme and started work on a permanent magnet alternator. The alternator was a flat-disc type that is popular with the DIY crowd [1] [2]. My dad even dug out his old EE motors book and some “real” engineering was done (like with math and stuff), but the design just did not scale very well at all to tiny magnets and tiny coils. It is very likely that I overlooked something important in the electrical design which caused such crummy performance.

Here’s a picture of the rotor I build to hold the 0.125″ diameter rare-earth magnets. It was turned from 2″ mild steel and was an adventure to make in and of itself:

Here’s a shot of the test rig. They may not look it, but those wires are suspended well above the lead screw. Even so, this is definitely not the safest setup in the world:

The one that worked (Stepper Motor)

Eventually, I gave up on the alternator and took the advice [Evan] gave me several days before, which was “use a stepper motor.” A stepper motor is basically an alternator running in reverse:

So I dug one out, wired the windings in series, and hooked an LED to it. Turned it by hand and the light came on! In about an hour, I turned a new drive shaft and had a working windmill model!

This drive shaft was made to couple to the motor directly and is a single piece.

The turbine

The model’s turbine assembly is based on a nice, cheap wooden spool. 3 spokes give students a place to attache their custom blades with masking tape, which are easily removed before the next class. I made 10 spools and only had one spoke break in a day of using them for class. The broken one was easily repaired with school glue at lunch time, so no big deal.

Here’s a picture of a spool just after gluing the spokes. The countersink in the middle presses onto the taper on the driveshaft to transfer torque:

And here is one of the more successful student-designed windmills:

Conclusion

The students really liked this activity. It was very hands-on and I brought along an analog ‘scope to display the AC wave generated by the stepper motor, which they really liked. Having the right tools to quantify the output of the windmills made it easy to get the students excited about competing to see who could come up with the most efficient design.

I also have a full set of pictures here.

DIY 3rd Hand

Michael — Wed, 04 Apr 2012 06:04:40 +0000

Here’s fun project that I did over the winter and just added some upgrades to. It’s an improved version of the “3rd hand” tool that is on many a workbench. I was frustrated by the all-metal one I was using falling out of position all the time when I remembered this Instructable from a few years back. Here’s my version of a coolant hose based 3rd hand tool:

Follow the bump for more details on construction!

—-
The design began, as usual, on paper. It’s pretty simple, but since I’ve started keeping track of projects in a proper notebook I took the time to draw out the parts.

The base began life as part of some complicated lab apparatus that I rescued from the garbage. It’s an inch thick and provides plenty of stability:

I drilled and tapped 1/4″ NPT and 1/8″ NPT holes for the coolant hose bases. The starter kit from Reid came with one of each size:

I really like this trick for starting threads on the mill and/or drill press. It’s pretty simple – chuck the tap in a drill chuck and turn the spindle by hand while applying pressure on the handle. This way, you can be damn sure that the tap is straight and concentric with the hole you just drilled. Be careful to keep light pressure on the spindle while backing out so that the return spring doesn’t strip out the threads. Since the taps I use don’t have hex shafts and might slip in the chuck under extreme pressure, I usually only start the threads like this and finish with a regular tap handle.

The thing wrapped in orange is a handle that came with a lathe chuck which conveniently fits this drill chuck, as well. It’s wrapped in orange to remind you to NEVER, EVER leave it unattended in a chuck. If you try this technique yourself, be sure to unplug the machine or pull out the switch interlock before turning the spindle by hand.

The arms are 1/4″ Loc-Line. Here it is test fitted into the base:

I wasn’t sure of exactly how I wanted to attach the “hands” to the arms when I started, so I got a kit from Reid Supply that had a couple of different nozzles. I decided in the end that I wanted something a lot stiffer than the arrangement in the Instructable, so I machined the “wrists” from aluminum:

Each wrist was turned with a shoulder to fit inside the last tube segment on the arm. I used roll pins to hold them in place and drilled and tapped a hole all the way through for a 10-24 set screw. The cap screws I used initially turned out to be really hard to tighten with finger pressure, so I recently replaced with paddle-style thumb screws.

Overall, I’m pretty happy with how the project turned out. The base is plenty massive to support a reasonably heavy board at full extension:

Another really cool feature of the tool is that, since the arms are plastic, you can use the “hands” as test clamps. Here it is being used to hold a micro solar cell for testing:

If you’re interested in more build photos, the Picassa album is here. If you’re interested in a kit or tips on building your own, leave a comment below

Hydroelectric Generator Model

Michael — Sun, 18 Mar 2012 05:27:57 +0000

I built this model of a hydroelectric generator a year ago as a visual aid for a middle school science class. I’ve gotten a couple of comments on my YouTube channel about it, so here are some more details in case you’d like to build your own.

System Overview:

From top to bottom, the model consists of four parts: a reservoir (“lake”), valve/”penstock”, turbine and a catch basin (“river”). Most of the parts were bought locally and should be available from your local hardware store.

Water Delivery System

The reservoir is a plastic container that is intended for holding cereal. It has a hole cut in the bottom to fit a sink drain. The drain is nice for two reasons: first, it is designed to seal against a flat-bottomed container and, second, it has a valve built into it. The pipe from the drain is connected via a brass fitting to some vinyl tube that ultimately delivers the water to the turbine.

Some heat and clamping had to be applied to mold the drain pipe so that it would seal against the threaded fitting. I also had to glue a small nozzle into the vinyl tube to increase the pressure with which the water hits the turbine. If I were to build this model again, I would probably skip the tube entirely and put a fitting with a small enough nozzle directly onto the drain pipe.

At the bottom of the model there is a second plastic tub that catches the water from the top. This model was designed to be used in a classroom without a convenient sink, so I needed somewhere for the water to go. The plastic containers are attached to the backer board with straps made from coat hanger wire.

Turbine and Generator Assembly

The turbine assembly is housed in a black project box. From left to right, it’s main features are:

Turbine
Splash shield
Test points
Lightbulb socket

The turbine itself is actually an air turbine from a balloon-powered car and happens to press fit nicely onto the motor/generator. It’s 4.5cm in diameter. The splash shield was cut out of a plastic bottle like the kind you would find ketchup or mustard in at restaurants. It has a hole in the top for the water nozzle. Originally I had the turbine enclosed all the way around with a clear cap on top, but there were some problems with interference and I wound up cutting most of it away.

There are four test points on the turbine box – two are connected in parallel with the motor for measuring voltage and the other two are in series for measuring current. In practice, I found that shorting the current test points together and just measuring voltage got the point across. There is also a socket for a light bulb, but the water pressure was not nearly enough to light one. I was able to get a bulb lit with compressed air at 40 PSI, but the turbine just couldn’t spin fast enough with water.

Here’s what the inside of the turbine box looks like. It’s pretty simple, just a few wires connecting the motor to the test points and bulb socket. The motor came out of an old tape deck, but any old hobby motor that fits your chosen turbine blade would do.

Things to do differently next time

The most important lesson learned from this project was that your common DC “hobby motor” works best at several thousand RPMs. At the couple hundred RPM this rig can turn the turbine at, one of these tiny motors can’t really generate useful power – not even enough to light an LED. An improvement would use a larger turbine and a small stepper motor as an alternator. The stepper motor can generate much more voltage at a lower RPM and the AC sine wave that it produces is an interesting visualization.

Hopefully that helps those of you who have left comments on the video. Leave a comment if you have any other questions or need pointers on building your own!

Sonic Screwdriver of the 10th Doctor

Michael — Sun, 22 Jan 2012 05:01:01 +0000

Around the beginning of October, a friend contacted me about making a Sonic Screwdriver prop for his Halloween costume. We kicked around ideas for a couple weeks and wound up with this:

We took a bit of artistic license with the design, but it is based on the screwdriver of the 10th Doctor. (see http://www.thinkgeek.com/geektoys/cubegoodies/8cff/)

The piece was turned out of aluminum and the final version has LEDs inside for lighting. Machining took about a week’s worth of afternoons, leaving me with a day left to make my costume :p

Build photos after the bump!

The piece started from a piece of 5/8″ aluminum round stock. It is made in three pieces (left to right in top photo):

Head piece
Collet
Barrel
Tail

Head Piece:

Starting the head piece:

Cutting the decorative features:

Aligning the head piece in the mill to cut the windows:

Cutting the windows with the mill. The brass tabs are to protect the turned finish:

Finished head piece. A glass bead will be glued to the top later. We chose to forgo the “crown” on the top to save some time.

Collet

The collet piece attaches the barrel to the plastic tube. I don’t have a good picture of it by itself, but this pic shows it fairly well. The collet is attached to the barrel with two screws:

Barrel

The barrel was the first piece to be started and the last one to be finished. It holds the batteries and LED that lights up the head piece. Most of the machining operations – boring, cutting the slot, drilling and tapping set screw holes, etc. – were done before turning the outside to avoid damaging the finish. The most interesting aspect of this piece is the mandrel I made to hold it when finishing the outside:

The mandrel consists of two aluminum cones and a center shaft made from a 1/4-20 bolt. One end of the shaft was held in the lathe chuck. The barrel was held between the cones (tightened with a nut and lock washer) and the right end of the mandrel was supported with a live center. This was the first time I had used a center with a project and the setup worked like a charm!

Tail Piece

At the bottom of the barrel is the tail piece. This holds the batteries in an provides some artistic decoration. I didn’t want to spend the time trying to thread on the lathe, so the tail piece is made in two parts – an outer aluminum shell and a threaded insert cut off of a 1/2″ bolt. The bolt piece has a 4-40 hole on one end and a small screw holds the two together.

Conclusion

All in all, I really enjoyed this project. Unfortunately, the friend who I was building this with moved to Seattle recently, so I can’t go back and take a nice set of glamour shots. I’ll be sure to do that early for my future projects… If you have any questions or want pointers on your own Sonic Screwdriver, feel free to leave a comment below!

Arc Reactor Halloween Prop

Michael — Mon, 07 Nov 2011 07:40:31 +0000

The night before a Halloween party I was browsing [Hackaday] and came across a last minute arc reactor prop. Having spent the last couple of weeks working on a sonic screwdriver for a friend’s costume, I figured I had to at least have *something* the next night and a quick-and-dirty Tony Stark costume seemed like just the thing.

Planning:

Seeing as how [Evan's] rep rap is still being built and there was no time for drafting besides, I couldn’t go the 3D printer route. It was easy enough to start from scratch and I had some components lying around

I thought about a couple of lighting sources – discreet LEDs, a cellphone backlight, surface mount LEDs, and EL wire – but discrete LEDs seemed easiest given the timeframe. The backlight would have also been cool, but would have required a color gel. As for power, I was originally going to power the LEDs with a watch battery, but I wanted a way to switch them on and off and also to be able to replace the battery easily. A single watch battery was more than sufficient to light all the LEDs, though:

Construction:

Using PVC pipe for the case was an easy choice given my past success with sensor node enclosures. I cut a 0.75″ wide piece of 3″ PVC and painted it silver. The tube around the outside is a piece of 0.125″ ID vinyl hose. I bent a piece of brass rod to fasten then ends.

To light the prop, I used eight high-intensity blue LEDs with 1K resistors around the edges of the case just like the demo I made for OSHW ’11 back in September.

The silver paint did not stick very well at all to the PVC, so I had to re-glue several of the LEDs. Using primer would have been a good idea.

The positive leads were long enough to reach to the center, so I just soldered them together there. A piece of copper tape helped bridge the gaps. The ground bus was wire-wrapped.

To make the “arc tube,” I fastened magnet wire to the vinyl hose with copper tape and wrapped it around a few times. This was a perfect use for an old spool of wire that had come undone and gone all “rat’s nest.”

To diffuse the light, I glued a piece of printer paper to a lens cut from a scrap of polycarbonate(?) sheet.

I made the little center bit from a steel washer, driller alternating holes for decoration:

The back of the piece was corrugated carboard. I glued some aluminum foil to it to reflect light towards the front.

To wear it, I just glued to the piece to a shirt and poked it through a gap in the buttons of a top shirt. I had to pin the top shirt just underneath to add some extra support, but it worked pretty well:

The wires lead to a 3 AAA battery case in my front pocket. Popping out the middle battery was a perfect “switch”!

BOM:
The whole build was completed in less than 5 hours, with a minor re-glue after an hour of walking around with it. Out of pocket, I spent $1.20 on resistors at Radio Shack. The total bill of materials was less than $10.

3″ PVC x 0.75″ – $0.50
3″ strip of aluminum foil – $0.07
8x blue LEDs – $2.50
8x resistors – $2.00
sheet of paper – $0.05
magnet wire – $0.01 (?)
copper tape – $0.01 (?)
Battery case – $3.00

Quick Review: Maker Beam

Michael — Wed, 31 Aug 2011 06:23:35 +0000

I was super excited to get a shiny new kit of Maker Beam today, so I thought I share my first impressions of it. Read on for the details!

Maker Beam is a “Mini T-Slot” aluminum extrusion. It is very similar to other products like 80/20, but Maker Beam extrusion is 10mm x 10mm. The small size makes it perfect for small projects like enclosures, small fixtures and small to medium robots.

One of the big attractions of Maker Beam is that it’s T-slot profile can fit a piece of cardboard, plastic, or a circuit board. Since this was the main reason I wound up buying it instead of Microrax, I was extremely disappointed to find out that it doesn’t actually fit pre-made circuit boards that well. The t-slot is roughly twice as wide as the thickness of a standard PCB (shown below next to a Maple Pro), so boards will not fit in snugly. There is an indentation in the bottom of the slot that is designed to cradle a PCB, but it’s too far back to hold parts that have components near the edge (eg. Arduino). Proto/perf boards and cardboard from boxes fit nicely, though.

The kit comes with a nice assortment of pieces and lots of hardware for putting things together. As numerous ~~trolls~~ commentators on Sparkfun point out, the angle brackets are marked in Tau radians, but there are only three angles to choose from, so it shouldn’t be a problem to pick the one that fits where you want it to.

Of more importance is the selection of length of pieces you get. There are plenty of pieces in the kit and they’re sized appropriately to match the included brackets. There is about 5.78 meters of extrusion in the kit total. You could probably get a lot more for a lot less, but the kit does come pre-cut, which is worth a lot in terms of time and quality of cuts. That said, the ends of the pieces are unfinished bandsaw cuts. For $130, it would have been nice to have finished ends. Or at least de-burred ends…

Another problem with the Maker Beam system is the choice of capitve nuts vs. captive screws. In Maker Beam, the screw heads slide into the T-slot, leaving the nut and a bit of screw hanging off the connector. Personally, I don’t think this looks very nice in a , though I imagine that it would have been much more expensive to get custom nuts to fit the profile. Someone on Sparkfun suggested that you could drop a project and damage the screw threads, making it impossible to get apart. I doubt that (worst case you strip out a screw and have to toss it), but I am concerned about the screws getting snagged on stuff like carpet and wires…

All in all, I think that Maker Beam is promising. The profile looks nice and the kit fits together well. If you have some specific needs that can be met with a kit of Makerbeam (like I did), then I’d get one. I don’t know if I would go so far as to recommend it just to have around, but I do wish that makerbeam.com would come up already and start selling bulk extrusion. I think I’d buy a dozen meters just to keep around for custom cuts when needed.

Mote Build Log 5: Pogo Pin Jig

Michael — Mon, 18 Jul 2011 17:40:51 +0000

If you’re familiar with embedded electronics like Arduino, you might have noticed that the Cirque (which is what I decided to call the mote just now) does not have the usual ISP header found on other AVR boards like the Arduino and clones. Since all the pins are broken out, we figured “what’s the point?” – especially since you only need to program the Arduino bootloader once and can use the UART from there on out to load programs. The prototypes have been programmed by attaching wires to the appropriate IO lines and sticking them into a USBTiny.

This is incredibly tedious and error prone, as you might imagine. Fortunately, automated testing of circuit boards is an extremely common problem, so someone invented Pogo Pins – fancy little pins that are spring loaded and have tips that fit into circuit board holes.

I set out to make a fancy test jig for the ~~Cirque~~ Lisa so that we could program and test them *before* installing the screw terminals and without having a crazy mess of wires everywhere. I did the machining and jig assembly, then [Evan] soldered the test board together. Here’s the result:

Pretty awesome looking with all those pins, no?

Both Sparkfun and Adafruit have tutorials on making pogo pin jigs if you’re interested in making your own. Both shops also sell them, but the ones in this jig came from Sparkfun:

Read on for pics of the build process and a cool video of what I think I need to build next ^_~

I started the build with the stabilizer plate. This piece of plastic will help keep the long pins straight in the jig:

During assembly, one of the ATmega pads lifted on this board, so it was used as the base for this jig. The board was bolted to the plate and used as a template for the pin holes:

The drill press had too much vibration to make these tiny holes accurately, so I used a milling machine instead:

Perfect fit

Test fitting all of the pins. A welding tip cleaner came in handy to clean out a few of the holes:

Cutting some nylon spacers that will fit between the board and the alignment plate:

I used a scrap of 0.25″ aluminum to make the base for the jig. The slot in the middle isn’t functional, it just came with the scrap. The holes are being tapped for the 4-40 all-thread that will hold the jig together. The rods will be held in the holes with Loctite:

Assembling the jig:

(Almost) finished product. The alignment rods will be cut down from where they are in this photo:

Something to aspire to:

Mote Build Log 4: 2nd Generation

Michael — Tue, 05 Jul 2011 02:41:00 +0000

The first generation of senor boards were a great proof-of-concept, but they had a few problems. For one, they were big. It’s easier and cheaper to make small cases. Second, the pin headers weren’t round, nor were the mounting holes perfectly on-grid. Third, the mounting holes were some weird size that was smaller than even a 4-40 screw. The silkscreen didn’t also didn’t come out legibly, which made things difficult when plugging in wires.

Long story short, there were a lot of improvements to be made. To get around the limitations of Eagle, [Evan] drew up the second generation of boards in KiCAD, taking advantage of the human-editable XML file format to lay out parts like the screw holes and terminals with precision that would have been difficult to obtain using only grid snapping. KiCAD also allow the use of the TopoR auto-router, which generated the sweet looking organic traces.

The new motes also omit the LED on the XBee disable pin. This pin is pulled high to tell the XBee to sleep, so having the LED on it wasted 5mA or so during the phase when we would be trying to *save* power. We chose different resistors for all the other LEDs, which saved a few more mA.

Overall, the MKII design is quite nice and we’ll be using these motes as the basis for some upcoming aquarium monitoring projects.

Tune in next time for a build of the test stand that will be used to program future MKII mote boards!

-Michael

Read more for a tip on programming ATmega328/P chips with AVRdude and Arduino

PS – An issue we did run into was a subtle difference between the ATMega328 and ATMega328P. The “P” stands for “pico power,” and there are a couple extra registers on the 328P that aren’t available on the regular 328 that do things like disable the brownout detector to save precious uAs in super low-power conditions. We used regular 328s for the first round of boards, but ran into a problem because AVRdude only knows about the 328P (device signature 0x1E 0×95 0x0F) and croaks when it sees the device ID for a 328 (0x1e 0 x95 0×14).

The easiest thing to do was trick avrdude by changing the device signature in /etc/avrdude.conf for the ATmega328P to that of a regular 328. The two chips are otherwise identical as far as programmers are concerned, so the other parameters are fine. This worked great for reading/burning fuses, but the Arduino IDE has it’s own version of avrdude, so it needs to be changed there to burn the bootloader. The good news is that the Arduino bootloader has its *own* device signature, so once it’s on the chip Arduino will think it’s a 328P and it will work fine with unmodified versions of the software.

Mote Build Log 3: Enclosures

Michael — Wed, 29 Jun 2011 05:48:14 +0000

In this installment of the Mote Build Logs, I’m making enclosures for the first generation prototypes. I wanted to keep the enclosures round to mirror the design of the mote and make them clear so you could see all the blinky lights. The cases are open around the edges to allow easy access to the screw terminals. They’re designed to be “backpack rugged,” not weatherproof. One is basically a shell so I can toss a mote in a bag and not worry about it getting banged up.

Read on for details on how they were built!

Cases

Each case is composed of two halves made out of 0.25″ acrylic. The material was first sliced up into square on the table saw, then rounded using a bandsaw and circle jig.

Since it was just that much more cool looking, I decided to hollow out the bottom half of each case so the mote could sit lower and be that much thinner. The mote boards didn’t come pre-cut, so I decided to use the mill to round them out as well. Since I would be cutting 15 pieces total, I made a nice jig out of aluminum to use to bolt the circuit boards and cases to the rotary table for cutting. Below is a case blank bolted to the jig plate:

Case blank being milled:

I decided after the first prototype that it was smarter to mill the case blanks *before* rounding them off so that I could use clamps in the corners. The screws in the middle worked great for alignment, but had to be removed on-by-one during hollowing, which took a lot of time.

The mounting holes in the bottom half of each case were marked with a center punch, drilled, and tapped for 4-40 machine screws (by Josie, my lovely assistant <3)

After the first prototype, I also milled a groove in the top to help seat the lid against the screw terminals and let the mounting screws catch a couple extra threads in the bottom. Holes were also drilled in the top so that the terminals could be accessed with a screwdriver:

A test assembly. The screw terminals on this version of the mote couldn’t be placed with precision in Eagle – so they’re not perfectly round, which would have been easy! They had to be lined up by eye, instead, which didn’t exactly work every time. Some had to be widened, but they all wound up usable enough for a first prototype run, though:

Circuit Boards

Since the circuit boards were already soldered (not a good idea, BTW), I raised them up on a piece of MDF so that the terminal pins would have somewhere soft to dig into, providing some more support. They vibrated a lot, but since the bottom of the boards wasn’t flat, using the mill was by far safer than the bandsaw.

Before milling:

and after:

Results

Here are a couple shots of the finished product:

Complete with a fancy sticker on the back! This first batch was built for my research in the Networks and Systems Optimization lab at NMSU (http://nsol.cs.nmsu.edu):

Next time…

We get a new version of the circuit board designed, manufactured and assembled

Mote Build Log 2: MK1 boards

Michael — Tue, 21 Jun 2011 05:05:22 +0000

Assembling and programming first batch of manufactured mote boards:

Since we couldn’t get the resolution to solder an ATMega 328 with our home-etched copper boards we made a design in Eagle and sent it off to be made at [Advanced Circuits]. They were expensive ($33 each!), but the Chinese suppliers were closed for New Years. Although they weren’t able to be cut round, the new boards came out quite nice.

(I don’t have a pic of a bare board, but this one has only SMD parts)

To solder them, we used a $20 drugstore toaster oven controlled by a Reflow Toaster Controller from Sparkfun.

We tried some solder paste, which worked horribly and bonded many pins on the first ATMega together. For the rest of the boards, [Evan] added some extra solder to the pads and fluxed the boards. Then I placed components, using the flux to stick them to pads. A quick trip to the oven and they were soldered. A couple boards had a handful of components that had to be touched up by hand – mostly LEDs.

When the SMD components were soldered, we soldered the minimum number of screw terminals and loaded the Arduino bootloader. Below is a pic of a board wired into a USB Tiny AVR programmer. The crystal pads on these boards were a bit tricky and one board got bricked once the clock fuses were burned, but [Evan] busted out with l33t assembly skills and set up another AVR as a clock source so we could rescue it.

Here’s a mote board fully populated with screw terminals and XBee being programmed with FTDI breakout board:

In the next installment, I’ll be cutting the boards round and making some fancy cases!