Stokes’ ProjBlog

A journal documenting innumerable, mostly terminally in-progress undertakings. Nerdiness abounds.


How to build a pressure sensor for (effectively) free April 1, 2009

Filed under: Miscelaneous Projects — Stokes @ 2:29 pm
The construction of a dirt-cheap pressure sensor.

NB: Despite the date, this actually works.

Andrew Sempere recently credited me for giving him an idea for a pressure sensor he’s currently using in a project. It was something I discovered accidentally, but further research revealed that the technique has been documented elsewhere. Regardless, I still think it’s pretty cool.


Random doodle: Spider-Bot June 11, 2008

Filed under: Miscelaneous Projects — Stokes @ 12:15 am

Mechanical spider conceptI haven’t had much time to work on any of my previously-posted projects in recent weeks (or months, for that matter). I’m just finishing up work for the Computational Art course I started in February; I did some interesting things that I’ll post here once I’ve finished the write-ups. Most notable is a small Propeller-based robot for teaching little kids some of the key concepts of programming. At the moment, however, it’s still more of a sculpture than an interactive piece.

But, on the topic of robots, I had an idea for a mechanical spider and used a little downtime at work a while back to produce a 3D sketch. I roughed out an animation to see how it worked. No, the animation to the left does not loop correctly; I’ll explain that later.

Like almost all the mechanical spiders that people have been producing lately, it’s based on the brilliantly clever Klann Research and Development design. Apart from cosmetic details, I made two small changes:

First, the inner and outer pairs of legs are offset slightly; the inner legs are slightly forward. The mechanical spider design is really more crab-like than spider-like, as all the legs operate on parallel planes. Moving one set of legs forward attempts to give it a slightly more spidery feeling.

Second, the motion of the leg pairs has been offset by 30 to 120 degrees. This was also an attempt to give the ‘bot a more spider-like appearance by roughly approximating the asymmetric gait of a stalking spider. I’m not sure if it’ll work in the real world. Putting the legs out of phase is what made the animation non-looping; the animation would have to be much longer to contain a looping cycle of all legs. Plus, I wasn’t very precise when it came to offsetting the motion, so I wasn’t entirely sure where the loop was going to occur, anyway.

I’m not sure I like the serrated edges on the front of each leg. Most of the mechanical spiders people build seem to have them. I thought they may have a practical purpose, possibly in climbing, but I’m now fairly certain that they’re just cosmetic. But being overdone, I may try to think of something else. I’d also like to make the front and back legs somewhat different-looking; the uniformity is another feature that makes such spider designs look crabby. I might also try to make the inner and outer legs slightly different, should I actually build the monster. I think I could very probably do it; axles and spacers aside, it is designed to be constructed from flat stock of the same thickness, which I could probably laser cut at the Fab Lab in an hour. Preparing the vector files in order to do the cutting would take longer, however.

But, that’s yet another project for the pile.


‘The LegoLCD Project’ December 23, 2007

Filed under: Miscelaneous Projects,New project! — Stokes @ 5:23 pm

Last month, I briefly mentioned the serial LCD I’d dug out of storage. I have a number of ideas for it, such as using it as the display for a Python-based MP3 player. Whatever I do with it, however, I need to put it into an enclosure.

The LEGO LCD and another Quatro system brick. The squares on the grid underneath them are one inch on a side; the coin is a US quarter.A while back, I saw something interesting: the LEGO Quatro system. Whereas Duplo is twice the side of a standard LEGO brick, Quatro is twice the size of Duplo brick. It’s very clever: toddlers can be given Quatro bricks, then use them with Duplo bricks when they get older. The kids can then use the Duplo bricks with standard LEGO bricks when they get older still. In any case, some gargantuan LEGO bricks seemed perfect for some sort of project or another. I didn’t have any specific idea in mind when I bought them, but a pair of 2×4 bricks ended up being the perfect size for the serial LCD.



Come up and see my etchings December 9, 2007

Filed under: Miscelaneous Projects,The Meter Thing Project — Stokes @ 9:05 pm

My first attempt at PCB etching: a carrier for a SMD IC.I finally got around to doing some PCB etching. For my first experimental attempt, I made some little carrier boards for an SMD IC: a M62364FP digital/analog converter, intended for the analog meter project.

It’s been more than a month since I did the toner-transfer with a clothes iron to the copper-clad board (some incredibly thin stuff I bought at the MIT Swapfest a while back), but I’ve been reluctant to break out the ferric chloride and do the actual etching. The transfer was only moderately successful; there was a small degree of smudging. I don’t think the paper moved; I may have used too much pressure and/or heat. The smudging would have been acceptable for a board with larger traces, but it was enough to short some of the board’s traces. I had tried to scrape away some toner with an X-Acto knife before the etching, but that was only moderately (if at all) successful. I may try scraping away the tiny shorts with a diamond-tipped stylus; I think I have one around, somewhere.

The etching took a remarkably long time. I’d pre-heated the ferric chloride by placing the bottle in a tub of warm water, and the ambient temperature was probably 65°F, but it took nearly 30 minutes to complete etching. I etched two, one after the other, and each took about the same length of time. I should have probably left it in even longer; it could have removed the shorts.

While this wasn’t the most successful attempt, it was my first try. I’m optimistic. Once I get some heavier copper-clad board, I’m going to try making the motor controller board. More board, along with some 3A diodes, is in the mail.


Slowing down November 4, 2007

Filed under: Miscelaneous Projects,ProjBlog — Stokes @ 5:13 pm

Despite my best intentions, I’ve been neglecting the project blog. I’ve had a number of things going, however:

  • Minor technical contributions to a Dorkbot Boston Halloween show. I hacked together a peristaltic pump to make a Furby vomit blood.
  • Broke out the old serial LCD display I’ve had in storage for a long time. I built a cable for it and did some basic Python scripting to drive it. Not sure what eventually will become of it.
  • I’m considering doing NaNoWriMo this year. I’ve let my writing slide; this would be a good kickstart.

All of this has made me realize something about my life. Here it is, in the form of a flowchart: