Category Archives: DIY

New Chorder

I’ve been playing with chorded input devices for years, and got the itch again recently.

CNChorder
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3D Printing KC Talk

I gave a quick primer on 3D printing as a Keeping Current (CS departmental) seminar yesterday.

It’s not a great standalone deck but posted (in reduced quality, gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=/path/to/output.pdf /path/to/input.pdf is good magic).

It seemed to be well-received, printed objects were played with, thoughtful questions were asked, I think this is the first time I’ve given a 3D printing primer to a wider group and not been asked the “guns” question.

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Lab Fridge Repair: Thinking with 3D Printing

I’m posting this because it’s such a nice example for the standard “What are 3D printers really good for?” question.

When I got to the lab today, I was told the can chute in our mini-fridge was broken. Inspection showed that too many of the little plastic inserts/bushings that retain the bars were missing and/or broken. This is a years-old cheap GE minifridge, so it isn’t even worth looking for OEM replacements.

Now we get to the “Thinking with 3D printing” part: I plucked one of the remaining ones, went over it with some calipers, transferred the measurements into OpenSCAD, and printed one off to test fit. The ID was a little tight, so I adjusted the model, printed 6 more, and fixed the problem.

In case the model is useful for anyone else: OpenSCAD and STL.

Important Details:

  • This took like an hour from start to finish, and wasn’t the only thing I was doing at the time. The printing itself was around 1 minute per insert.
  • The new inserts are better than the originals. Not quite as pretty in some ways (though they are blue and glow-in-the-dark, because that’s our current junk filament), but the fit is considerably better.
  • That “iterate” step in the middle, where you just try it and adjust if needed is among the most beautiful things about 3D printers.
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T510 Touchpad Resurfacing

TPReplaced

I found a forum.thinkpads thread while looking into another touchpad issue recently, and learned two important facts:

  1. The bumpy touchpad texture I never loved that had worn off my T510 is just a sticker.
  2. Those stickers are replaceable.

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Singer no.42 Swingarm Repair

I’ve posted before on the slow restoration of my old 201-2 and its cabinet, last time I noted that my cabinet’s swing-arm wouldn’t auto-deploy, which prompted some discussions with other folks about the mechanism. One of those other pieces of input was someone kind enough to tip me off in the comments of my last note about this that there were a couple sets on ebay, which I looked at for details, then ended up buying one of for $22 shipped. I really only needed the lower pin and spring, but the spares are nice. This is what the seller pictured, and the light and camera are better than mine, so I’ll just use their picture, because it was well packed and exactly as described:

SingerSwingarm

I now have mine working and have detail photos and measurements from the process that should make it easier for others to figure these things out. It’s actually a really simple mechanism, the following two pictures are pretty much all you need to know about how it goes together and works.
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Inspiron 11-3000 Hinge Screw Defect

Inspiron113000Hinge

The Inspiron 11-3000 I’ve been carrying around developed a rattle the other day, and today I decided to open it up.
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New Data Integrity Tools

I’ve recently added a couple tools to my standard set, and have at least a 4x improvement in the safety of my data by doing so.

The process was complicated a bit because I’ve become very sensitive about only depending on FOSS tools (ex:As much as I like SublimeText2, I stopped using it because it once demanded to be updated before it would run.), but frankly I think that constraint produced better results than I would have reached without it. Because it was something of a hunt, I’d like to recommend the particular tools I settled on, in particular are KeepassX, Attic, and Seafile, described individually below.
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Quick Laptop Sleeve

HalfIn
I noticed I was scuffing up the not-my-laptop that I’ve been carrying, so I did a little “30 minute” sewing project (that actually took over an hour because I’m apparently retarded) after I burnt out on other things for the evening.

The intention is a little sleeve that will be snug enough to retain the laptop, and let me slide it between [note]books, etc. in a bag. That means a little long, with thick hems on the open end for retention, and no flaps, fasteners, or protrusions to hang up on other things in the bag.
Basically, I measured the wrapped length and width of the machine (to accommodate for thickness), cut a piece of fabric I had around to the full wrapped long dimension (+1.75″ for hems and clearance) and half the wrapped short dimension (+1″ for seams), hemmed the short ends, folded it in half, ran a seam down the sides, half-assed wrapped the first 2″ of each side seam, and called it adequate.


Upside:

  • I can still sew well enough to go from conception to part on something trivial almost instantly.
  • My neglected sewing gear is still in working order.
  • My vintage sewing machine got her recommended periodic exercise and lube.
  • The finished product is functional and looks fine.

Downside:

  • I initally cut the circumference of the machine … in both directions. 1.9 sleeves worth of fabric!
  • One day, I will sit down in front of a sewing machine and thread it the right direction the first time. That day was not today. Bobbin thread/direction? -Easy. Complicated path through the tension and take-up? -Easy. Passing the right way through the needle? -Derp. I’ll claim it’s the Singer vs. White thing if challenged.
  • I had to look it up and still managed to use the adjustable hemmer wrong in two different ways, one hem failed to fell, the other is not really straight.
  • I added allowance for generous 1/2″ seams intending to cut after … then sewed 1/4s and had to redo the side seams to make it snug enough.

Using my venerable old machine always makes me feel like it and 3 generations of my family are judging me when I do something inept or half-assed on it, which probably makes my projects better.

I think I’m satisfied. I’d like it to be just a hair snugger, but the fit is pretty good and snugger would have run the risk of finishing then not being able to get the machine in. I think I want to make some kind of companion pouch for the power brick, but I’m not sure how, an attached pocket would ruin the slip-between-things-in-my-bag functionality.

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WNR3500L Repair

Some years ago the KAOS lab bought a number of Netgear WNR3500L routers to use as network glue. A pair of them have been in constant service since 2011 in the lab and machine room, and both of those died in the last two weeks. I’ve finally satisfactorily tracked down the culprit, and figure it’s worth a quick write up.

The WNR3500L is a bit of a false-promise machine; it was sold as an “open router” with excellent community firmware support, but it has some pretty extensive blobs that mean it really only runs versions of DD or Tomato with a small range of 2.6 kernels.

I initially just swapped the first one to die out for a spare (which happened to be flashed with Tomato instead of DD, it was an experiment when they were first set up), and reloaded most of the settings by hand (we failed to save or document many of the settings elsewhere. Our fault.) until I had time to investigate. When the second one died, it became urgent.

WNR3500LScrew

Conveniently, the WNR3500L has a 3.3V RS-232-like serial port (115200/8/n/1) under an easily removed panel, retained by one small torx screw/pin thing (Both are out in the picture while I was figuring out which side was which).

WNR3500LBP

This leads to another victory for the Bus Pirate. Any 3.3V compatible UART adapter would work, but the bus pirate has much nicer cables for this sort of thing. In retrospect, those headers are correctly sized to just plug the female harness ends directly, but I used clips out of habit.

It turns out they were booting right up with only warnings, but the configuration was sufficiently garbled that neither the WLAN nor the Ethernet ports were coming up. I blew the first one’s settings away (note: at least on the old version these were running, reboot TWICE after clearing the NVRAM to get back to a consistent state: the first time it writes default values, the second time it boots cleanly). With the software-only nature of the problem established, I took more time to investigate the second one, at which point…

nvram show
[1310 lines excluded]
size: 32782 bytes (-14 left)

Well, There’s Your Problem.

Turns out the tiny little log fields for monthly traffic statistics filled up the nvram and were causing configuration corruption, and thus failures.

There are some forum threads and bug reports on the matter, and it was fixed about two years ago with a test to prevent writing past the end of the file, a default setting to automatically delete traff logs after 12 months, and various other enhancements. Now that we’re up and running again it isn’t desperate, but it looks like there is a DD release from mid-2013 with the fixes applied that still supports these things, and they are probably due to be re-flashed to keep this from happening again.

Lessons:

  • My home OpenWRT on a TP-Link 1043ND uses a connected USB key for logging and such. This is a much better behavior (like most things in OpenWRT: DD-WRT appears to be kind of an unmaintainble mess).
  • Keep an eye on appliances like routers, they’re still just computers.
  • Back up your damn configurations, or at least retain copies of the information required to regenerate them. Regenerating settings, especially when it involves manual tasks like MAC address hunting, sucks.

Other notes:

  • These things’ bootloaders appear to always look at 192.168.1.2 through the non-WAN ports for a tftp payload named vmlinuz. There may be a way to disable that, but I think I’d prefer to leave it on, since it only enables local attacks and provides a rescue mechanism.
  • The WNR3500L has a documented weakness about WAN-LAN throughput with various firmwares. Our uplink is actually good enough for it to matter, so perhaps one of the newer versions will improve that.
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Singer no. 42 Cabinet Swing-Arm

One of my previous posts about my Singer attracted an email conversation with another owner about the swing-arm mechanism on the no. 42 cabinet. Unfortunately, the end-of-semester insanity struck before the matter was settled, and I am still unsatisfied with what I’ve been able to figure out.

Now that I’ve had a bit of time, I pulled apart my mechanism and took photos, shared below. I’m reasonably certain that if the mechanism is complete and correct, the arm will automatically deploy when the leaf is lifted. Unfortunately, I’m also quite sure that the pieces I do have are inadequate to support that functionality, and I can only guess what the other bits might be.

The larger diameter end of the part I do have matches the diameter of the holes in the hinge, and the smaller-diameter end matches the hole through the swing arm and base.
My best guess is that there are several objects similar to the pictured pin, one of which protrudes below the table into the catch hole of the swing arm through the holes in the hinge mechanism, springloaded “up” such that it retracts when the leaf is out, and is depressed by something protruding from the hinge-hole in the leaf pinning the arm when closed. The pictures sent by the other owner show what looks like the end of a similar pin protruding into the bracket, but it does not extend any where near far enough to retain the arm.

Posted partly in the hopes that my pictures will help other folks with their cabinets, but also if anyone with a no. 42, especially if it has a working swing-arm mechanism or parts that are not pictured, sees this I’d love some more information about how they’re supposed to go together.

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