I ain’t afraid o’ no ghost

With the Pac Person costume complete, it’s time to crank out some ghosts. Construction is pretty much just like the Pac Person, except there are two strands of lights instead of one. Every ghost gets a blue strand (for when it’s vulnerable) and a body color strand (red or green) for those times when it has an insatiable hunger for bloodPac Person.

Knowing that making Pac Person required about five hours to sew one strand of lights on, I decided I needed a faster approach. I set up the fancy quilting hoop – it’s an embroidery hoop on a stand. I can see the point behind it.  For quilting, where you would have a lot of stitches in one place before you have to move the fabric, it ought to be pretty good.  But for sewing lights on a piece of fabric?  I spent more time taking the fabric in and out of the hoop than I did sewing.


I needed a solution. Over dinner I mentioned to Susie that what I needed was a quilting frame about five feet in diameter. About the size of the kitchen table. And that’s when she realized that the kitchen table could be a quilting frame.  We pulled the two sides apart, neglected to insert the leaves, and there you have it.  Not quite as good as having a five foot diameter frame, but close enough.  Also – if you try this at home, it’s a really good idea to sew both strands at the same time.


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Waka Waka…

In previous posts, I’ve gotten a sewing machine and I’ve bought wire lights.  I’ve also made allusion to ghosts.  By now it should be obvious…

Real Life Pac Person.

(The console games attempted to promulgate a false gender binary on susceptible young players.)

I managed, before this weekend was out, to sew a Pac Person cape and attach yellow LED wire lights to it.  I did it not because it was easy, but because it was fun.  Making the cape is the easy part. It’s a two-fold cape with one section removed to yield a 3/4 circle cape.  Neck cutout is about a 12″ collar.  Velcro allows it to be taken down to half that, or a velcro extension tab expands the neck to about 21 inches.  This should fit anyone from eight year olds to All Pro defensive linebackers.


LED coverage is stronger on the left side than the front, and I’m debating whether to go back in there with another, shorter strand of lights or whether to just go with it.  All the players are going to know this is Pac Person – it’s yellow, it’s hitting Power Pills, and it’s running like its life depends on it when the blinking stops.  Illumination brightness is more than adequate for indoor play.  I expect it will burn through three sets of batteries in a seven hour installation.

Those LEDs took about five hours of hand sewing.  Oh yeah.

Raspberry Pi – First Light

The big upcoming project uses the Raspberry Pi for brains.  Actually, it uses four of them, one per ghost.  Last week I got them powered up and actually started configuring them.  Simple USB-WiFi adapters are plenty good enough for what I’m doing, and I’m pleased to report that they work flawlessly.

In fact, everything works flawlessly.  This is a totally “plug it in and it works” kind of thing.  Plus, the Pi comes with both Minecraft and Mathematica.  This is the first time in two or three years I’ve felt complete, unadulterated joy from a computer.  The purity of the experience is remarkable.


(brightness, contrast, and effective gamma have been tweaked to compensate for the exposure being completely blown out by the bright monitor behind it).

CPU power feels about like a PII-450 running a modern distro, but the microSD card feels very slow.  No matter – it won’t be heavily taxed in the upcoming application.

Built Like a Battleship

New addition to the Secret Underground Laboratory:


A Singer Model 99K. Serial number strongly suggests manufacture in 1946. The 99 family was considered a portable sewing machine – at 31 pounds, you could move it anywhere an ox could drag it, and this model is considered “half size”. The machine positively radiates solidity. Accepts standard, modern needles; I’m not sure yet about bobbins. I tried a “New Singer” bobbin and it was too thick to fit in there. I know they stock two different sizes at the fabric store, so I can try the other size and see if I get any luckier. Otherwise, I have the four bobbins that it came with, so I should be OK.

Edit: Bobbin is a Singer Type 66. These are still fairly common, and fit oodles of modern machines. Should have been obvious: a 99 is a smaller 66.

Obligatory action shot:


Someone check the doorbell…

My house was built in 1929.  The doorbell is presumed to have come later, but maybe not much later.  It had been getting a little unreliable the last few years (!!!) but it all came to a head two weeks ago.

Anyway, the first step to healing is to admit you need to disassemble the thing.


And a detail of those switch contacts:


So, those machine screw ends are shorted together when the doorbell button pushes the brass spring down onto the (corroded) ends of the screws.  Repair methodology: file the metal parts until they’re shiny and new looking.  The material that the threads screw into is about 50 laminations of plain old paper.  Amazingly, it has held up through at least sixty years of outdoor use.

Wire Lights

For an upcoming project (hint: the big reveal will be April 25th, but you’ll get a good glimpse of it here before the Big Day) I need a whole bunch of LEDs I can put onto some fabric. The traditional solutions have problems.  Typical “flexible PC board” tricolor LED strips are too stiff and too expensive.  A ton of discrete LEDs is too time consuming and, except at surplus prices, way too expensive.  Enter “Wire Lights” – two parallel strands of copper bell wire with surface-mount LEDs soldered between them.  Wired in series with the entire strand is a series dropping resistor sized to make the whole string light up at 5 volts.  Specified current draw is 1 Amp, but I’m going to need to measure that.  Not really visible in daylight, but they show up well under “normal” indoor illumination and they’ll be great in a slightly dimmed exhibition space.  Hmm…


Fixing Battery Corrosion in a Mini Maglight

About twenty years ago or so, I bought a Mini Maglight to supplement one I had bought about twenty-seven years ago. Both of these use the itty bitty incandescent bulbs, neither one being anywhere near new enough for the fancy modern white LEDs. They work, anyway. Or, they did – until the batteries in the newer one leaked.

Normally, this wouldn’t be a big deal. You replace the batteries and get on with your life.  In this case, though, there was a complication. The leaking battery was completely stuck inside the flashlight barrel. I tried banging the open end against the back of legal pad, and I tried that a lot. No good.  Evidently it was time to take it apart and push out the dead cell.

There are at least two versions of the incandescent Mini Maglight running around, and my two were of different generations. I had taken the old one apart before, but the new one was a bit befuddling. First, field strip the easy parts – take out the bulb and then just pull on the “do not remove” outside bulb holder until it pops off.


This leaves you with the inside bulb holder, the barrel of the flashlight, and one immovable battery. It’s time to move the immovable. I didn’t have a pin punch the right size, so I grabbed a cheap, junky Torx screwdriver that would fit in the access holes at the very back of the inside bulb holder and whacked it with a hammer.


This resulted in squat. I was deforming and slowly hammering my way into the battery instead of pushing it out. Judo is too subtle, I’m switching to Kyokushin: hit it harder.  About ten good whacks with a small hammer and I started to actually move the battery.  A bunch more and it finally came out.  Finally, switch to a larger drift (in this case a, uh, Uniball Vision ballpoint pen…) and gently tap on it until the inside bulb holder falls out of the threaded end.


Inspection of the flashlight barrel revealed the reason the battery wouldn’t come out – when the cell leaked, it dumped potassium hydroxide into the bore.  This reacted with the aluminum barrel forming hydrogen gas (always a crowd pleaser) and potassium aluminum tetrahydroxide – aka “crud”.  Oh, and it also formed a corrosion pit in the aluminum – luckily not all the way through the metal.

Cleaning out the corrosion is done with a 20ga shotgun bore brush threaded into a cleaning rod and the tool spun with a drill.  Wear a dust mask and eye protection.  Bear in mind that the friction will heat up the aluminum, so pay attention and stop to let it cool at intervals.


Assembly is the reverse of dismantling.

Controlling a Dollar Store Solar Dancing Elephant

By now you’ve almost certainly seen those little dancing toys that move when their solar cell gets illuminated. The things fairly well litter the “everything in here is yours for just one stinking dollar” stores. I’m not going to disparage them as toys – to be honest with you, I think some of them are pretty entertaining.

Then again, when have I ever not dismantled one of my toys?

The goal here is to take a solar dancing elephant and hook it up to a computer. When something interesting happens in reality, the elephant starts wagging its ears up and down. I had thought about using it as an email alarm, but that’s just depressing. Instead, I think I’ll scrape the current weather off of the NWS and make it dance in response to something like temperature or rainfall rate. Elephants should get excited when I rains, I guess.

Step one is to crack the elephant open. What really bothers me is that some day, someone is going to arrive on this page after they googled exactly that phrase. Crack the Elephant Open. The mind boggles.


Anyway, with your elephant nicely bisected, note that the solar cell and some electronics are in the top half of the shell, and the lower half of the widget is all moving parts. The ears are pretty finely counterweighted.  It doesn’t take much force to get them moving. This is a good thing because that solar cell isn’t going to make a lot of power (milliwatts, maybe? ) and the electromagnet that it operates isn’t very big. Incidentally, the astute observer will note that there is a tiny, tiny bare die chip under epoxy on the circuit board, and that the coil is connected to it through something that looks like 40ga wire – aka “man! that’s some awfully fine wire there!” So do be careful.  If you break that wire, you’re pretty much out your one dollar.


Next step – clip the wires right at the solar cell (red one is positive, natch) and connect a long-ish two conductor wire to each of the leads going to the board. This is what you need to power your elephant. The cell on there makes about half a volt, but I’ve put five volts across the circuit with no ill effects. Evidently, the design has some wide tolerances. 🙂

Final step – connect the wires to the ground (pin 18 was as convenient as any) and to a data pin (pin 2 is the least significant bit) on a connector for a parallel port. I added a parallel 100 ohm resistor that I really didn’t need, but I figured it might help the elephant live longer. Then finally all you have to do is find an old-school laptop with a parallel port and plug it in. A few lines of C, and voila!  You’re (announcer voice) controlling elephants from Linux.  And seriously, once you’ve done that, the rest of your day is going to be all downhill.


Controlling things comes down to manipulating the parallel port (and no, this will not work through a USB-to-Parallel converter).


void main(int argc, char **argv){
unsigned int value=0;
if (argc > 1) {


int port=/*  0x378 */ 0x3bc;
int res = ioperm(port,5,1);  /* allow access to io port plus next 5 addrs */

And that’s all there is to it.

Installing thick (15mm) 2.5″ drives in Dell drive carriers

I have a bunch of Dell 1955 blades that I’m reconfiguring. They used to be a fairly garden-variety supercomputer – 530 blades, Infiniband network, made it onto the Top500 list in 2006 (UNC’s “Topsail” cluster). Topsail reached the end of its usable life for that sort of workload (how progress does march on, no?) and was headed to surplus. The group I work in at Renci intercepted it and turned it into a Big Data cluster. The first-generation Nehalem cores aren’t so hot anymore, but having 1060 SATA channels for running Hadoop on… dude! You’re resurrecting a dell!

The only real hitch was storage. The blades came with 40 gig disk drives – enough to hold a boot image and not a whole lot more. The machine is long out of maintenance at this point, and the biggest drive Dell ever officially supported in there was probably a 300 gig part, so off to third-party land we go. I scored a couple of Hitachi 750 gig drives a year ago and they worked great. Now, Western Digital has started volume shipments of their 2TB 2.5″ drive. Naturally I ordered a pair of those.

Best laid plans, etc. When I went to install them in the Dell carriers (with the 40gig drives removed), there was a slight clearance problem The metal corner brace gets in the way of letting the drive fully seat, so the fourth mounting hole doesn’t line up with the drive:



…so it’s off to the Secret Underground Laboratory. Fortunately, the carriers are cast out of zinc, rather then being made out of steel, so they’re really quite easy to modify. I cut away some of the corner bracing of the first one with a Dremel tool, but that took about fifteen minutes. I have 530 of these to do, so I want something a lot faster.

Jamie would use a tablesaw and face shield, but I decided to go with something a slightly more subtle. I grabbed my total-piece-o-junk Jorgensen mitre box – never buy one of these, folks. The cast bed comes from the factory out of true, and if you have to pay a machine shop to resurface it, well, it’s cheaper to buy a good one.


Which is why I don’t mind using it to cut metal. I hate that tool, I want it dead so I can throw it away. You understand.


Once you have a nice notch all the way down to the side rail, just grab the rail with one pair of pliers and the excess tab with another, and twist. The zinc will fail right where it should. Clean up the burrs with a file, and you’re in business.

Then install the drive in the carrier, the carrier in the blade, the blade in the bladecenter, and let Rocks reinstall Linux on it over the network.


Now I just need to do this 527 more times…

Bose Headphone Repair

I have a pair of Bose Reality-Cancelling Headphones – not too effective against human voices, but they do a good job of cancelling steady noises like air conditioners and computer fans. I like them well enough, but I wouldn’t recommend them anymore.  Maybe the Panasonic version?

The problem is that after five years or so, the pads that go over the outside of my ear have started to come apart at a seam, exposing the foam. The solution is simple, of course: sew them back together. The hard part is the lack of room to work. I cut off a sewing needle to roughly 3/8″ and ground it back to a point. Surgical forceps work well to hold the seam back together temporarily, then a pair of long-nose pliers is what it takes to jam the short little needle through. I ending up using a second pair of forceps as an anvil and as as extra set of fingernails to grab the needle when it comes through. I didn’t even attempt any kind of running stitch or fancy lacing/trussing/macrame, I just tied off each stitch as I completed it and moved on to the next one.

_DSC0014 _DSC0010

Now, the failure is running around the inside of the cushion – when I repair one section, another one pops loose.  Pretty soon I will have sewn all the way around, and shortly after that I suspect the material will simply fail entirely.  At that point, I don’t know.  I’ve been known to limp stuff along just for fun.

Current score:  Patience vs Rampant Consumerism: 1-0.