Category Archives: DIY

The Ugliest Little RepRap Stepper Driver

Posted on 2010-04-12 by pappp

I’ve been playing with my CNC Mill project a little bit in some “spare” time(= time I should be working on things for school, but can’t focus), and just got my third RepRap Stepper Motor Driver v2.3 working after some replacement parts and judicious green-wiring.

I bought three drivers as kits, because they were cheap and well regarded, but the boards are largely surface-mount, and the first attempt to populate them didn’t go well, thanks to distorted lead frames and UK’s shifty surface mount equipment. With a little bit of hand soldering to fix lifted pads, I got two of the three boards going, but one of them …ignited… when tested because of a lifted ground on the main IC. The bad board has been sitting in it’s bag waiting for me to do something about it for most of a year now, and the other night I realized I could probably remove the chip, order a replacement Allegro A3982 from one of the electronics suppliers for a couple dollars, and try again. Pulling the chip by hand lifted four pads, but left it looking workable, so I picked up a pair of spare chips from DigiKey (who, for a pleasant but startling change, only charged me a very modest shipping fee).

My replacements arrived earlier today, and I couldn’t resist taking a crack at it. As the title suggests, this resulted in a UGLY but working driver board (click for larger):
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Check out the run of magnet wire across the bottom of the board, up through a via, and then under the pad it goes to. That is some quality fabrication (also, I checked, that path never carries much current, so magnet wire is OK). The other fixes are all relatively easy (and large-current) runs across one side of the board.

This time, instead of catching fire and destroying an IDC cable, connecting power and my supremely ghetto-rigged test circuit (a 555 timer set up to generate a pulse train on step, and some buttons and switches to control direction and enable) resulted in a smoothly turning motor. Success. I’ll probably only have to make one more small electronics order (remember that melted IDC cable…) and all the drive electronics will be together to run it from a EMC2/Linux box.

The hangup now is the connections between the axes and the drive nuts: my old bent-steel-sheet brackets were not square enough, and were causing walking and uneven tension and all manner of badness, but I haven’t managed to design a replacement I’m both satisfied with and able to build/source. If anyone has an idea for mounting a 1.25” long, .56” flat-to-flat hexagonal coupling nut to a metal panel 1” away from the rod the nut rides on, which will take large lateral torque and remain square to the rod, let me know. I have a half-baked plan with some modified heavy L-brackets, but there must be something better.

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NAK Build Party

Posted on 2010-04-08 by pappp

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My research group will be building our new (smallish) research supercomputer NAK:(NVIDIA Athlon XP cluster in Kentucky) on Friday, April 16, 2010 from 10A to 4P in FPAT672. UK students and other interested Lexingtonians are invited to come help with the build, so if you would like to play with the guts of a big cluster, you will be welcome at the (re)Build Party.

If you can come up with a better phrase (with a better acronym) for the “NoBuPAG” principle discussed in the machine description, that will be really welcome too.

NAK will provide a testbed for continuing research into building tools for performing useful compute work on GPUs. It presents a different model than the conventional GPU as an attached co-processor to powerful compute nodes model, which has thus far proven impractical to program for. Instead, NAK treats the nodes as “Nothing But Power And Ground” (and a network interface…), and will be running all of the heavy compute on the GPUs themselves, through a mechanism extended from our MOG project.

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Gettin’ my Buildycrunk On

Posted on 2010-02-20 by pappp

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I’m getting my Buildycrunk on, so are all these people. You should be too.
I’ve seen coding, grading, knitting, antenna fabrication, card games, board games, and all kinds of awesomeness.

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Buildycrunken #2

Posted on 2010-02-11 by pappp

Collexion (check out the bitchin’ new webpage, courtesy of nuex), along with our friends at Third Street Stuff and Coffee, are holding Buildcrunken #2 on the evening of Feb. 19th at Third Street Stuff.

Last time was amazing, and many excellent things were accomplished. Everyone rest up, come up with something to hack on, and show up; a grand time will be had by all.

There will probably be more detailed information online shortly; I am slightly out of the loop because I missed last week’s Collexion Lunch (due to allergies), and this week’s Wednesday Collexion meeting due to to sticking around, keeping the lab open, and helping some of my kids finish up tedium lab week in EE281 (where we make the kids design and build something that takes at least 4 TTL chips, by hand).

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Reference Manager

Posted on 2010-01-27 by pappp

I’ve decided I need to start using a reference manager utility. My old system of keeping a text file full of BibTeX entries in a folder with pdf’s, with an extra “file:” field for the file name of the document is a little crude, and starting to break down as I get large piles of documents for some topics.

Because my PSY562 class this semester is largely using readings from HFES journals, I’m going to use the pile it generates as a testbed to find something I can use generally.
My requirements for a reference manager include:
* Accepts and Emits BibTeX Citations
* Capable of linking citations to files
* Storage format which is (roughly) human readable
* Easily transported database
* FOSS
* Works on Linux
* Limited dependencies (I’d prefer to avoid Java or Qt)
* Works without network connection

The most widely used solution, EndNote, fulfills very few of the above (plus, interoperability dickishness, but fortunately there are lots of projects to make reference managers floating around the ‘net that seem promising. Unfortunately, most of the promising ones are dead. The best of the actively-developed bunch seems to be Referencer. Referencer is a C++/gtkmm app (so it plays nice with my XFCE4 environment), with a Python plug-in system (Should I ever choose to use it), reasonably limited ties to the various non-GTK gnome libraries, and stores it’s records in XML. It looks remarkably close to what I want, and has some features I didn’t know I wanted (preview icons, tags) that are pretty useful. I think it’s going to be a keeper, but would love to hear what other people are using.

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Kentucky Touch screen / Natural User Interface meeting

Posted on 2010-01-22 by pappp

Earlier tonight I attended a sort of open-access seminar on multi-touch user interfaces, catalyzed by an EE senior design group working with Awesome Inc. to create a large multi-touch wall for the outside of their space. The attendece was wonderfully diverse on account of the announcement hitting the professional, academic, and hobbyist communities in Lexington (more events need to propagate like that!). Attendees included several members from the Lexington IEEE chapter (co-opted as a chapter meeting), a number of local creative types, many students from UK, and several other interesting folks.

The discussion centered around the CCV effort of the NUI group, and was fairly solid, although I would have appreciated a bit more technical depth. I actually ended up dominating a couple conversations on account of being better read in the area than most of the other attendees, and don’t consider myself particularly well-versed in multi-touch display technology. I still don’t really understand TUIO, I was rather hoping someone there would be able to explain it.

One small downside, I still get the uncomfortable feeling that everything said or done at Awesome is being sucked in and analyzed as a potential source of financial gain. The culture there always seems exploitative (or at the very least commercial) instead of communal, which is very unfortunate, as they have set up a nice space, and seem to be attracting interesting events.

I really am attracted to open-access, discussion based topic seminars like this, and would love to see more of them happen. There are lots of good efforts to bring that sort of thing to Lexington, from a seminar series Dr. Finkel is attempting to arrange this semester (based on students and faculty giving short presentations on neat things they have found), to Collexion and Dorkbot’s regular meetings. This is not the first time I’ve been after this sort of thing either, for a while the UK LUG was running some decent events in this vein, in particular I remember a successful LUG event on PyGTK, but the LUG is several years defunct…again…because those of us who were active didn’t have time to keep it going on our on (and be students), and no one else stepped up. I think some of the short-form lecture series like ignite have had events here as well, but those have never seemed as useful to me.

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A Tiny Plastic Dot

Posted on 2010-01-20 by pappp

(This is very much an example of one of the little manic episodes that make me a good generalist/appear high functioning)
The left touchpad button on my laptop (Thinkpad T60p, hostname Monolith) has been “limp” for a while. It bothers other people who use my machine, because (objectively) it really does feel very wrong, but it had broken gradually and I had acclimated enough that it didn’t bother me. Last night I started paying attention to the problem, and it became maddening, so I decided to see if I could fix it. I looked at the problem last time I had the machine apart, so I knew there was a torn plastic tactile dome to blame. It is (as best as I can make out) impossible to order just the appropriate domes, and a whole new touchpad is 1. defeatist, 2. about $12 from shady ebay sellers, and 3. requires waiting for it to be shipped. I decided a better (ie. creative, free, immediate, and credit-card-fraud free) solution would be to go rummage in the parts bins, find a sufficiently similar tactile dome in something dead, and install it. The closest match I could find was the keyboard domes from the corpse of my old VPR Matrix 180B5 (The worst made laptop I have ever encountered. Every bit as fragile as one would expect something made by a Best Buy house brand to be, even though it was basically a re-badged Samsung P10. Polystyrene is not chassis material.) I now have a partial match (it’s a little too weak, and not “snappy” enough) installed, which is good enough to keep it from being bothersome.
Thinking about tactile domes reminded me of a fabulous article I read (I thought) about them several years ago. It turns out it was a much more general article about handheld devices, but it really was fabulous. The article is “Handhelds of Tomorrow” from the April 2002 issue of Technology Review. Ideo has a PDF available outside a paywall. The part about the tactile bubbles was one little subsection about Peter Skillman, who was “the hardware guy” at palm/handspring (weird corporate history).
The search for the article reminded me of a previous kick on the work of one of the other important palm/handspring people, Jeff Hawkins, who in addition to being a founder of both companies, is doing amazing work in neuroscience as it relates to computing, and has written a book On Intelligence and given a awesome TED talk on the topic.
Hurrah for (hypo)manic episodes?

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PoS Toy

Posted on 2009-12-28 by pappp

I scored a (at least mostly) working Point of Sale terminal from the trash at the nearby location of a fast-food sandwich chain named for a mode of mass transit. It’s a pretty nifty little piece of hardware, a Micros Eclipse 400498, based on a 1Ghz Pentium 3, 512Mb of RAM, and normal (ish) PC-BIOS. It has a broken WinXP install on it now, I think it shipped with an older NT version, because the drivers are all fucked up. The fun part is the attached goodies: a 3-track magnetic stripe reader (credit cards, etc.), 2-line VFD display, and a 12” touchscreen (only 800×600, but pretty crisp and good colors).

I’m thinking it will make a bitchin’ jukebox. Scroll the track information on the VFD, put a touch-flow-esque interface on the touchscreen, hook up some speakers, etc. One of the housemates suggested a barmonkey (it could even process payments), but that is a WAY more involved project because of the valve rigs, and I have plenty of unfinished involved projects right now.

It is however being obstinate about drivers and alternative boot devices, and the manufacturer (micros) seems to believe that not providing any drivers/manuals/support of any kind will enforce support plans/upgrades/create security by obscurity or something, because their website is supremely unforthcoming. There don’t appear to be any WinXP compatible drivers for the various hardware, so the best choice is probably to try for Linux. Its not wanting to boot off USB devices (despite the BIOS’ claims that it will), doesn’t seem to like having a 2-channel ATA cable attached, has no CD drive, and has repeatedly failed on the wubi-install-from-USB trick, so it will be exciting to get going. Maybe some sort of netboot stunt.

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Dorkbotlex #9

Posted on 2009-12-21 by pappp

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After missing a few due to travel and other obligations, I’m back to attending DorkbotLex. #9 was last Saturday (the 19th) and, as is traditional, I’ve posted up some pictures on flickr. This month’s presentations were both electronic music projects, one set of hardware hacks and one piece of prototype software. As always, very cool, and a great source of energy for creative endeavors.

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CHDK on the SD770 IS

Posted on 2009-12-17 by pappp

The camera handling for my last post reminded me to check to see if progress had been made on the CHDK port to for the Canon SD770 (the little point-and-shoot I have). There was a promising effort about a year ago, but the developer disappeared without releasing the partly functioning code, and it was quickly abandoned. Apparently someone else stepped up in November; there is now a (roughly) fully functional boot image available for the SD770.

CHDK features provide at least partial fixes for all my major complaints about the 770; the exposure override settings allow the flash to be kept under manual control through power cycles, even when the other features are on automatic, the exposure behavior can be more precisely controlled to hide noise issues in low light, and all the CHDK toys are now on hand, so I’m not missing any expected features.

Right now I just have a spare small card set up, but the process is non-destructive and simple, especially on cards <4Gb, so I’ll probably set up the pair of 1GB cards I usually use with it shortly. Anyone with a Canon camera should go set up a card with the appropriate CHDK image, it really does improve the camera.

EDIT: There are a couple bugs, the only serious one being that the camera crashes when using auto white balance with the version of CHDK in the linked thread loaded. I don’t have time to get into another environment to fix it.

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