Breaking Birdfeeders

If you follow me on Twitter — which you probably do, since that’s the only venue through which I notify anyone of these posts — you’re probably aware that I’m way into looking at birds, and I have a big stupid birdfeeder hanging outside my window towards that goal.

Three out of four residents in the Hester-Tiedrich household agree: Looking At Birds is good

The feeder pole is clamped to our balcony railing, which is a pretty common configuration and you can buy poles and clamps like these at big hardware stores. HOWEVER, most deck railings made of 2×4 planks are apparently designed so that the wide side is parallel to the ground, because I was having a really hard time finding a clamp with a frame larger than three inches or so. Since our railing has the wide side perpendicular to the ground, that meant I had to splurge a little on a compatible deck clamp:

Yes of COURSE I bought it anyway.

So, whatever! I spent like $40 on the mounting system for this cheap feeder. WHATEVER!!

At the beginning of September, I started seeing a downy woodpecker at my feeder. THIS RULES because woodpeckers are rad and some of my favorite birds, but I noticed it was having a hard time accessing the food — woodpeckers are zygodactyl, meaning their toes are separated such that two toes face forward and two toes face backward, kind of like a chameleon. This is great for grabbing onto the trunk of a tree, but not ideal for a hopper-style feeder where the food is at the bottom of a little trough; the woodpecker outside my window kept grabbing onto the ledge of the trough and flipping upside-down underneath it.

“no, it’s fine, this is what I wanted”

I told you all of that so I could tell you this: I bought a woodpecker feeder.

It’s a wooden suet feeder with a tail prop (sort of like this one by Nature’s Way), so graspy birds like woodpeckers can grab onto the vertical surface and use their tails for support. Suet, if you’re not familiar, is animal fat rendered into a hefty brick (nice), and you can get varieties mixed with crushed-up bugs and stuff for use as bird food (NICE).

So I bought this sort of on a whim because I was in a hardware store for an unrelated reason and I “””accidentally””” walked into the birdfeeder aisle. I realized I had nowhere to hang it in view of my window, which meant I would have to buy another $40 in hanging accessories, and then I realized I was standing in a hardware store.

For less than five bucks, I grabbed a big S-hook, a P-clamp and a metal mending bracket that doesn’t start with a letter.

I’m furious because even if it was an L-bracket it wouldn’t have spelled out anything cool.

There’s not much to say about this build, since it took about five minutes to put together: the rubber liner on the P-clamp prevents it from sliding down the pole, the bracket has one hole for fastening and one hole for the S-hook, and the hook is what the feeder itself hangs from. I used a wingnut on the bolt because it meant I could adjust it on the fly without having to bring tools outside, which proved to be a good idea because I’ve already moved the thing a couple times.

EXTREMELY EXCITING

And there it was! Two birdfeeders on one pole, because this household is ruled by anarchy.

You can tell how long I’ve been putting off writing this because in my photos the ground outside our building isn’t covered in half a foot of snow.

It became evident that there was a flaw in this design: because of the way the hanging wire attaches to the feeder, it was parallel to my window. That means I had a really good view of one side and couldn’t see the other side at all.

“wow i love to eat animal fat rendered into a brick, this is a good day for me, a bird”

“hey”

This was fixed by putting another tiny S-hook immediately above the big one, rotating everything downstream of it ninety degrees. And there you have it: a finished thing.

I don’t think this was a particularly mind-blowing or impressive build, but it’s always nice to remember that you don’t have to feel constrained by the limits of the world around you. BUILD A BETTER ONE, WITH MORE BIRDFEEDERS.

who does this guy think he is

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Mounting an Expedition in Mounting

Last month my good friend Norrin gave me a Cintiq 13HD for my birthday, and by gosh is it a treat to work with. A Cintiq is something I’ve fantasized about owning since back when I was using a Graphire3 tablet in highschool and I can confirm that it absolutely lives up to my own personal hype.

Now that I have an expensive tool for professionals I can FINALLY become good at art. That’s how it works, right

Another thing I’ve always fantasized about was…having a bunch of computer monitors mounted to movable arms. I’M NOT REALLY SURE WHY I thought that was so cool, but it was at the top of my list of Super Cool Details About Where I’ll Live When I’m A Grownup.

Life Goals

Now that I’m A Grownup with a new monitor burning a hole in my desk, it’s definitely time to fulfill those weirdly-specific dreams. I started looking around for a good monitor mount and chose the Ergotron LX Desk Mount, which is a little pricey, but, screw it, we’re talking about childhood fantasies here, let’s go hog wild.

This image of a computer screen on a white background is exactly as hog wild as my life gets.

The Ergotron is pretty much exactly what I was looking for, which is a sturdy desk clamp mount that has a really wide range of motion. When drawing on it the Cintiq obviously needs to be low enough that I can reach it comfortably, and I like being able to move it into the air to reclaim desk space when I’m not using it. Securely fastening something above the desk is also a cool way to prevent my terrible cats from knocking it over or getting paw prints all over it, which are coincidentally their two favorite pastimes.

Like basically all monitor mounts, the Ergotron comes equipped with a VESA mounting interface, which is a standardized bracket for mounting flatscreens. Almost all TVs and PC monitors come with a VESA mount at this point, making it really easy to attach them to things.

And I’ve officially run out of synonyms for the word “mount”.

For whatever reason, though, the Cintiq 13HD doesn’t have a VESA mounting point — it doesn’t actually have any kind of mounting features at all, other than two parallel slots on the back so you can use the crappy little leaning stand it comes with, which feels really easy to knock over or collapse just by gently nudging it the wrong way.

A cat designed this.

Obviously, I’m not going to let a little thing like “the way the manufacturer intended me to use their product” to get in my way. This seemed like a weird design oversight, so I tried to see if the Internet Hivemind had developed an agreed-upon solution. Oliver Wetter of Ars Fantasio came up with a really cool idea: gut a tabletop easel and drill some dang holes in it. He’s even using an Ergotron arm too!

I like this idea not only because it’s functional but also because it’s using a “traditional” artist’s tool for a digital application. It’s like…whoa, man. Art???

I sashayed into my local Michael’s and bought the first tiny easel I could find that met the important critera, which was a back frame that would roughly fit the VESA bolt pattern. The only thing I could actually find was the Artist’s Loft Mini Display Easel, which I guess is Michael’s store brand. It was really cheap and you can absolutely tell why — as soon as I took it out of the box, a loose screw fell to the floor. Nice!

Roughly the exact opposite of nice!

Luckily I don’t give a heck about the moving parts besides the clamp slider, so I disassembled the rest. All that left was the back frame, the static lower jaw and the sliding upper jaw of the clamp. I sort of got cold feet about trusting a shoddy assembly of wood planks to securely support an Expensive Thing, but the connection between the lower jaw and the frame (two screws in the back) actually seems pretty solid. Good enough!

Everything on my desk is black so I’m sorry for the terrible contrast in the upcoming photos. Alternatively, we can just pretend it’s artsy.

The VISA MIS-D interface on the Ergotron has two square four-bolt patterns, one slightly larger than the other, so I figured there was a decent probability of the easel fitting one of them.

“This will probably work” is all the planning you ever really need.

So I slapped the easel against the Ergotron VESA mount to figure out where to drill the holes and was met with an inevitable fate: the easel frame was not the right size for either pattern of four screwholes. In fact, it was just the right width to fit exactly between them, which is hard to see in my picture but which I swear to you is true.

CURSE YOU, LAWS OF PROBABILITY

That means I could shift the frame slightly to the left or right and the two sidebars would line up with the large square pattern on one side and the small pattern on the other. That would make it slightly off-center, but whatever! Good enough!!

So I was getting ready to drill holes and was met with the inevitable fate next in line: since this easel had those stupid slidey legs, the frame has these big slots on both sides. These were directly underneath the only places it made sense to put the mounting holes.

CURSE YOU, ARTIST’S LOFT™-BRAND PRODUCTS

I definitely didn’t want to try drilling through those slots, because it would have probably caused the whole thing to splinter apart. So, gosh it to hell, I have a frame that’s exactly the wrong size enough to fit between my two mounting options, and there’s a big hole in the middle of the wood I need to mount to. What the heck!!

I was starting to feel like I’d have to find a different easel, and then one second later I was like “FRICK IT, PUT SOME ZIP-TIES ON THERE”

FRICKED

I suggest always keeping zip-ties around because they’re pretty good for quick-fixing stuff. They’re not the best solution for everything because they’re permanent enough that you have to destroy them to disassemble your fix, but not so permanent that I’d expect them to hold up to a lot of wear. They definitely have their uses, though, and this application actually seemed like one where they might work.

From the pack I had on-hand, each tie can handle up to 18 lbs of tension before breaking. The Cintiq 13HD weighs about 3 pounds, so four ties (one in each corner) should be plenty, even taking into account the fact that I’d be leaning on it while drawing.

The nice thing about using an easel is that it comes with those feet at the bottom — when I lower the arm to draw, those can rest on the desk and act to support it, almost like some kind of drawing easel or something. This keeps the Cintiq from moving when I lean on it, but it also takes a little bit of the force off the cable ties. Oliver Wetter up there suggests mounting an iPad stand or something similar to the bottom to give it some extra standing height, which could be useful depending on the height you like to draw at (or if you use a standing desk), but this works fine for me as-is.

Anyway, I still used eight ties (two in each corner) for redundancy’s sake. I know the zip-ties aren’t the best way to do it, so the least I can do is overdo it.

I realized upon taking this picture that I mounted the easel to the VESA bracket upside-down. I have a degree in mechanical engineering.

The frame slots actually ended up being the perfect length for this, and when everything was tightened I had a Cintiq-sized clamp that was nice and sturdy.

I didn’t want to just toss the Cintiq in there without any padding, however, and I loathe the idea of allowing anything as barbaric as unvarnished wood to touch it.

A few months ago I ordered some free samples of Sorbothane sheets for something at work. Sorbothane is a cool viscoelastic material that’s really good at absorbing shock and isolating from vibration, and it’s often used to shield electronics from those forces — I think they also make shoe insoles out of it. Unfortunately, it’s slightly too flammable to use in space, so I didn’t end up using it and had a bunch of scrap left over.

Waste not, et cetera.

It came in handy for this project — the stuff I had on-hand is low-durometer, so it’s pretty squishy. It’s also tacky, so I didn’t have to worry about it sliding around. I cut some strips to size so I had a layer on the top and bottom jaws, as well as some padding on the sidebars. The large strip in the image above has a weird little lip on it — that’s from the process they use to make it, and it’s usually waste material, but I used it here as padding between the edge of the Cintiq and the retaining ridge of the lower easel jaw.

Not shown is the piece that goes on the upper easel jaw, because gravity.

I think you can buy sheets of Sorbothane on Amazon, if you’re interested in trying it for something. The stuff in the picture is 0.080″ thick, but if I were buying new stock for this project in particular I’d want something thicker, like at least 0.250″.

This step is actually really important, because the easel only holds the Cintiq in one axis. If it’s not a tight fit, rotating the mount would cause the thing to fall out, which is a bad situation. The padding here increases static friction greatly, preventing it from sliding, and also allows you to increase the clamp force without having to worry about damaging the Cintiq.

You’ll note in the picture that I also put a couple dinky Command strips on the center bar of the frame. I don’t expect them to do much in the way of security; they’re really only there in an attempt to keep the Cintiq from shifting or wiggling when I’m putting pressure on it.

Anyway, all that’s left after that is to put the Cintiq in and tighten the clamp, and it’s done!

At the time of writing this, I’ve had this configuration set up for about a week and have used it to draw several times. The mount is super sturdy and doesn’t wobble at all; I’m a little wary of moving it by the tablet so I usually push it around by the easel legs and that’s easy enough. I might put a handlebar on there later if I feel like it but it definitely works as-is.

The Ergotron is definitely overkill as far as security goes, since its designed lifting capacity is 7-20 lbs. You may be wondering why there’s a minimum weight, but the whole thing is a spring-tension system. The weight of the load actually gets utilized when you adjust it, which is how you can move a heavy monitor up or down with the same amount of force. Even after adjusting all the springs to the lowest possible tension settings, I had a lot of trouble getting it to do what I wanted with such a tiny weight on it. Before I made any permanent attachments, I had to manually cycle the lift and tilt joints in particular to loosen them up. That’s a fancy way of saying I sat on the floor and painstakingly pivoted the hinges like a hundred times. The tilt joint in particular is super stubborn, and I ended up just getting it to the angle I wanted for drawing and leaving it that way. If I ever do add that handlebar, I might make sure it’s really heavy.

As far as a failure analysis goes, I think the two most likely points of failure are the lower easel jaw and the zip-ties. One nice thing about plastic zip-ties (especially black ones) is that it’s visually very apparent when they’re in bad shape. I’m going to be periodically checking up on the back panel to look for discoloration or stretching, because that signifies a lot of stress wear. If one unit is seeing a lot more wear than the others, I can replace it or strengthen that corner; if they all wear down really fast it might be necessary to rethink this system. Who knows, maybe they’ll last forever. The easel itself is a little harder to judge but that screw connection seems stable, particularly since it’s metal-on-wood in shear.

If I make another post next week with a picture of splintered planks and smashed Cintiq bits, I was wrong.

This was a pretty simple project and only took an afternoon to put it together. If you want to try it, I would not suggest this model of easel in particular — you can find better ones online in the $15-$25 range. You can get everything you need besides the arm itself for pretty cheap, too.

Power Supply Concept Sketches

Wow, today it’s me: your old friend Katie. You remember. Hello!

I’m designing the circuit enclosure and user interface for our power supply project, and boy do I have a lot of thoughts to share about that. I’m actually fascinated by the field of human factors, which is basically a fancier way to say “ergonomics”, which is itself a fancy way to say “remember that a human being will have to use your thing after you design it”.

I think most people consciously encounter ergonomics in a comfort-of-use way, like buying a weird curvy computer mouse or a weird curvy chair to make it slightly less uncomfortable to do your job all day. According to ergonomics, all you need to do to fix all your problems is add swoopy shapes to the objects in your life.

If you’re lefthanded, like me, ergonomics is usually the art of making things physically impossible to use.

Human factors is more than just preventing hand cramps or back strain, though: it’s basically the act of designing the interface between a person and a tool, both mechanically and cognitively. Yes, this is the most pretentious way I can think of to describe it.

At my day job, human factors usually comes into play whenever a component is designed with the expectation that an astronaut will interact with it, and we have to consider not just the torque required to twist a lever or flip a switch or whatever but also what angle they’re going to be approaching from, whether it’s visible to them during use, whether they’re wearing a spacesuit, bleep bloop et cetera. Basically, you don’t want a crewmember to accidentally flip like five switches at once because they were installed too close together and her gloves are huge, especially when the switches all do really important things like “make the crew not die”.

That’s a pretty extreme example, but the logic applies basically any time you design something for human use. Functional design is a really cool field and there’s a lot of theory behind it, and I’m probably not the best person to try to talk about it, so I’m going to stop.

WITH THAT IN MIND, I SPENT A BUNCH OF TIME DOODLING CONTROL PANELS.

You’ll notice some water damage, because Tom Servo jumped into the shower when I was taking a shower, then ran out of the bathroom and onto my desk and all the documents thereon. A common theme of this web blog is probably going to be Cats Ruining Everything.

My personal design process, when it’s at the point where it’s progressed to paper, is usually to start doodling things stream-of-conscious-style to develop an idea in what I hope is a good direction. That way, if I get to a dead end, at least I have a log of where my train of thought was going and I can pick up in another direction. For your entertainment, I’m going to try to step through what I was thinking when I drew that mess.

So, before we get ahead of ourselves, here’s the most important question for functional design: what is the object’s function?

In this case, the power supply circuit is intended to, uh, supply power. That’s literally it! You find something you want to push electrons through, make it touch the supply at two points (power and ground), flip the switch and then electricity happens from point A to point B. The user can adjust the DC voltage and gets visual feedback of that adjustment via a numerical output.

Read all of these up-to-down, right-to-left, like the world’s least-interesting manga.

First thing I did was put down all the components we were planning to use, including eyeballing their rough dimensions. Those are:

• Switch (x1) — power on/off
• LED (x1) — power indication
• Knob (x1) — output voltage adjustment
• Binding Posts (x2) — output voltage terminators
• LCD Screen (x1) — output voltage display
• Fan (x1) — internal airflow

Everything but the fan would be present on the front of the enclosure, and that’s what I was focusing on, so this is the last time you’ll see the fan today. Bye, fan!

Fan (Side): RIP 2015 – 2015

This is basically the universe’s simplest interface: there’s one switch, one dial, one display, and a place to attach a receiving power circuit. Not exactly a life-saving or complicated device. This is probably not an instance where human factors will make much of a difference at all, but it’s still worth devoting a little bit of thought to. Also, I enjoy pointless exercises in overcomplicating things.

Above my component checklist is the literal first layout that came to my mind, and it’s appropriately terrible. Even past that, it’s physically impossible — we want to just steal the display and integrated circuitry from that pocket multimeter from Norrin’s previous post, and a conductive strip on the back of the LCD interfaces directly with the PCB via the stripe of pins at the top here:

Is this these pinstripes I’ve heard so much about

The LCD only protrudes about a quarter-inch from the PCB, and there’s no easy way to add space between the two without rewiring it, so that leaves us with about three inches of unusable space on our control panel right below the display. From an aesthetic standpoint, this is not ideal!

Aesthetics by themselves don’t always contribute much to a tool’s physical functionality (and can often do the opposite), but I’m an artiste and if I’m going to build something, damnit, I’m going to try to make it look cool.

In addition to coolness, a tool’s appearance and interface layout is actually pretty important to how a user’s going to approach it. Stuff like button placement and mapping is important to how we “read” an interface; this is why the Up button on a videogame controller never makes your guy run left. This is something I think about whenever I design GUIs or engineering drawings or comics: is the intended user going to have any idea what the hell they’re looking at when they try to interact with this? Even if all the tools are there for your user to do what they want, will they be able to figure it out without you explaining it to them?

Applied to our power supply control panel: yes, probably, it would be very difficult to screw this one up.

Anyway, at this point I’ve written over a thousand words about functional design and I haven’t showed you any designs. Assuming we want the display at the top of the panel, that means this thing’s going to be at least four inches tall, so the rest of the interface should occupy that space in a functional, readable, eye-pleasing way. Easy!

Introducing Grandma the Clown

So at this point I’m just doodling different spatial combinations to try to find something nice. Unlike most power supplies, I want the control dial to have a static range: turn it 45° and it will always be 6Vdc, or whatever. That way I can put a graduated indicator on it, like a guitar amplifier; this is something I find visually appealing.

Our control knob will go to eleven. It’s a twelve-volt supply, so that’s actually kind of important.

I was imagining the dial with about a 90° throw, but then I picked up the associated potentiometer and started playing with it and realized it had almost a full revolution of travel.

This is dumb, but the drawings here go upwards on the right and then the notes go back downwards on the left. It didn’t occur to me that other people would look at these. Pretend it’s a case study in bad ergonomics.

I was kind of mentally insistent on the idea of having an acute dial range, so I was thinking about doing some circuit magic [sic]  to shorten the span. Knocking it down to 180° would roughly halve the control resolution, and this is the spooky territory where an aesthetic decision would negatively affect the tool’s function. This train of thought made me start thinking about adding another dial, and assigning coarse/fine functionality between them. The supply’s range is only 0-12Vdc, but when Norrin was testing the circuit I noticed that it still took some back-and-forth canoodling to get the potentiometer to land on the exact value you want. Adding a fine-control knob would help with that.

So with that in mind I started thinking about ways to artistically fill the space beneath the display.

Just add some diagonal lines, that should distract everyone.

I got into the idea of putting the display on an angled surface. I like this concept because benchtop power supplies are usually pretty low-profile and if you’re situated too far above your work surface it can get annoying and back-hurty trying to bend down enough to read a vertical display two inches off the table. Putting it at about a 45° angle means it should be legible both from head-on and above.

Oh My Gracious indeed

I like this idea because we’ve solved the empty space problem: pushing the display back a little means stuff can get wired up in front of it. I eyeballed the backshell depths, but they were all pretty similarly sized, so it wouldn’t make a huge difference what height I mounted them.

Read this one bottom-to-top. You probably had to scroll down to read this caption, so it’s too late for you.

I sort of drifted back to having one control knob on this page, because being stubborn is easy. At the top right I got to a concept I liked: control knob right under the display, power switch next to it, and the binding posts above the switch. Visually, this seemed pretty tight!

I scribbled on my first page of notes that I didn’t want to put the posts above anything important, since when in use they’ll most likely have wires drooping down from them and blocking anything beneath them. I figured it was alright to put them above the power switch, since it’s not something that needs to be visible or requires fine motor control. Nice, we have a design!

Two Screaming Robot Heads Pressed Together In Perpetuity

At this point I’ve put the second dial back in and now I’m trying to decide whether the dials or the binding posts should be on the inclined portion of the panel. Eventually, I settled on the first concept, proving that you should never think anything through.

“Too Tall/Weird” also describes my fiance

Now it’s time to put some real dimensions on this design, rather than just drawing it the way I think it’s going to line up. I put a healthy amount of empty “border” space around all the components; this is both visually snazzy and important as a keepout zone, so none of the components are too close together. Remember the astronauts? Think of the astronauts.

I put a little extra vertical space above and below the control dials — below because I don’t want a user to have to mash their hand into the table to use them, and above so I can add some cool labels to them. I also had to consider the fact that Norrin’s fingers are wider than mine, so the dials would have to be spaced further apart than I first thought they should be.

Now that we’ve quantified the design, let’s put it all together to scale! We’ll measure it out with a ruler and everything!

Hmmmmmm

This proved to be useful, because seeing it laid out to scale like this without artistic interpretation made me realize I hated this design. Adding the second control knob means one is partly underneath the binding posts, which I don’t want. I also realized that putting the posts ~3″ off the ground means that any test circuits are going to need longer wire leads, which isn’t always convenient. Never mind!

Hmmmmmmmmmmmm

Switched the control knobs and the binding posts, and this is much better. I drew this with the minimum height dictated by the keepout areas, but then I did some very advanced and scientific seventh-grade trigonometry and realized it didn’t actually need to get any taller to accommodate the multimeter circuitboard when it’s at this angle. Yay!

I tend to name subcomponents on the spot, if you couldn’t tell.

Here’s a quick count of all the components we’ll need (sans holes to be drilled/cut) and a little mockup of the full assembly. We’re putting this together from flat 0.118″-thick sheets of acrylic, and I like the idea of putting a 45° chamfer around all the sheets’ perimeters; that way you wouldn’t see their thicknesses wherever two pieces meet. Then again, we’re doing all the cutting by hand, and I have to see how good I am with our new Dremel before deciding that’s something I can actually get right. For that matter, there was definitely no need for me to dimension these pieces to hundredths of an inch, because there’s no way we’re actually going to meet that accuracy, but here we are.

The fan (remember the fan?) and the power cable will go in the back somewhere. We’ll also have a way to easily access the circuitry once it’s inside, in case it needs repairs or adjustments down the line.

So hey, we now have a housing concept, and all it took was six pages of notes and a ton of pseudo-intellectual rambling! NICE

Our First Project!

Hello! Katie and I bought a SNES not too long ago and we’ve really been enjoying it! Unfortunately, we’ve been spoiled by wireless controllers for nigh on 9 years now, so even though the SNES controller is one of the most pleasing controllers ever designed…

We’re little shits!

Tom Servo and Crow T. Cat had a tendency to fly across the room at ludicrous speed, catching the controller cords with their tails. This kills the SNES. That gave us a great idea: let’s take a standard SNES controller and modify it to be wireless! They sell wireless SNES controllers (you can find them on Amazon) but it’s all third party stuff that looks ridiculous, and both of us love the actual controller. We figured out what we’d need to do it, ordered most of the parts off of SparkFun, and then realized we had no way of actually powering the damn thing besides running through a thousand batteries while we figure out what we’re actually doing.

So!

That brings us to our first project! A benchtop power supply! The ones we were looking at were pretty expensive, and there’s not actually a lot that goes into making a basic power supply. Of course, as we bought the last two parts from RadioShack we found a $20 power supply that they don’t list online for some reason, but it was ugly as sin and we didn’t want your stupid power supply anyway.

We still exist! Seriously!

We found a pretty good tutorial on Instructables that served as a good starting point and made some minor modifications. We got almost all of the parts at RadioShack, along with some assorted resistors and a breadboard from SparkFun (and some acrylic for the case, from Menards):

Let’s take inventory, from left to right and top to bottom (almost all of these are listed in the Instructable as well):

• 10kΩ potentiometer, which we’ll use to control the output voltage
• 0.1µF capacitor, to use as a smoothing capacitor
• 2x 1N4001 diodes for circuit protection
• 1kΩ resistor, used in combination with the potentiometer to get the appropriate output
• SPDT switch to act as a power switch; we picked up a nicer power switch for the final product (not pictured) but this one is easier to use for testing
• 10µF capacitor, which will improve the response speed
• LM317TG voltage regulator, which will let us safely adjust the output voltage
• Connector for a 13.5VDC power adapter, for the input voltage
• Breadboard, because if we build the permanent circuit right away something would go wrong and catch fire

Not pictured: a heat sink to attach to the voltage regulator which will prevent overheating, a small fan to do the same, and assorted bits of wire.

Our design uses a 10kΩ potentiometer rather than a 5k because we thought it looked cooler, and that’s the best reason to make design decisions. The great part about circuits is we can totally adjust to that! We want to get up to 12V output (same as the original design) and our potentiometer has twice the max resistance, so doubling the static resistor gives a good approximation of where we want to be. The closest resistor we have to that is a standard 1kΩ, which should work fine. If we really wanted to get it precise, we could also wire up another 100Ω resistor in series, but we don’t really want to.

We followed the same circuit diagram as the original design, and our end result is a functional (and profoundly ugly) power supply!

The best thing since smoldering breadboard.

We have a working power supply, but we want something a little more… permanent than this. The next step would be to solder everything to a perf board (and attach the heat sink) but every RadioShack within a twenty mile radius was completely sold out of them and we forgot to put them in our SparkFun order. For now, let’s move on to some other fun stuff we can add to the power supply. A variable power supply isn’t very useful if you don’t actually know what you’re getting out of it, so we picked up a cheapo voltmeter that we could tear apart and transplant. This thing runs on a 12V, 33mAh battery which is honestly astonishing to me. I hate the idea of having a mobile, convenient voltmeter so the first thing I did was attach leads to the battery terminals so I could power it from the input of the power supply.I love the way the dial works. You select the output you want and it connects these traces via 16 unique patterns. The way it snaps into place is also pretty neat: 

The metal strips on the back of the dial aren’t just for conduction, they also act almost like springs to press the dial to the face of the voltmeter. The two metal ball bearings rest statically on the dial and fit into grooves on the faceplate so that the dial will “snap” into place. To no one’s surprise, I immediately dropped one of them onto a tall carpet.

I live here now!

All in all, a fun first day of mucking around. We’ll want to start building the permanent circuit and cutting down the voltmeter so we can just use it as a display, but we managed to output a variable voltage and lose several parts, so all in all pretty productive.