Here we go again. This time, I hope to actually post something once in a while. But I think there's a chance of that now that I've got something worth posting about. And that subject is my crazy project du jour.
You, dear reader, will see the progress of these crazy robotics, linux, or other projects as they unfold. I will also post information that I find useful as I work on these projects.
I don't care much for the themes that come with Thingamablog. In my opinion, the one called "trendy" is the least ugly. But I do know that if I were to try and perfect my own theme, I'd never get anything done and eventually get bored and quit before posting a single word. Therefore, I'm going with the least offensive theme for now and won't try and tweak it until later.
Yesterday, I completed my fifth motor controller board, containing two of Steve Bolt's Four Transistor H-Bridges The first was an old-fashioned SPST/DPDT relay controller, the second was based on a pair of BA6219B chips I salvaged from an old VCR, the third was a UCN5804B stepper driver, and the fourth was a set of pure transistor (TIP41B) H-bridges. Since I can now control up to 8 DC motors, and since I'm pretty sure I can throw future motor controllers together whenever I need them, I think I'll move my attention to sensors.
I think I'll start with such low-tech sensors as bump switches and CdS cells. I like the idea of giving my robot feelers, but I haven't seen a design for them that I've really liked. As for CdS cells, I think I'll just go with a four-cell design I found in Robot Building for Beginners
Branded: The Buying and Selling of Teenagers (Book ring)
I just completed a set of whisker-type sensors for my soon-to-be mobile robot. I had seen several such designs elsewhere on the Web, but each had elements I didn't like, such as that the antennas were electrified. I eventually arrived at the hybrid design shown below.
In this design, one end of a spring is soldered to a PCB, but the other end is left free to move. A U-shaped loop of wire surrounding, but not touching, the free end of the spring is soldered to the PCB. Then, an insulated probe is inserted into the free end of the spring. When the probe collides with an obstacle, the spring moves and makes contact with the loop, completing the circuit.
Here's the finished product.
If you've never heard of the old Home Brewed Computer Club, look it up. This was a group of hobbyists that met in the 1970's to discuss and build their own computers around the new technology of microprocessors. Among the results was the original Apple computer. Of course, I was way too young to have ever participated in that group, but the idea of building a computer rather than just assembling one is very exciting to me. As it happens, Make: recently linked to an article about a British home-brewed computer, the Chaos computer, which I found quite interesting:
"The computer described on these pages was started in 1977 with the gift of a Signetics 2650 microprocessor by Mullard. Attempts during the previous year to order an Intel 8008 and a 2650 from Farnell had all proved impossible, and this 2650 processor was finally obtained after my father drafted me a letter which I sent to the Managing Director of Mullard. The 2650 was an 8 bit processor with 32Kbyte address range and 256 I/O locations. It has 7 general purpose registers and an on-chip return address stack for subroutines with 8 entries. It was not possible to make data access to this stack or flush it to memory. "
Check out this gallery of unusual Chinese robots. There's robot rickshaw driver, a robot waiter, a robot pianist, and a robot tour guide, or " beauty robot ." Ooh, look, she's got her clothes off!
There's also a robot chimpanzee that's missing only a pair of cymbals. At least she feels pretty.
As for this guy... I just wonder why the builder chose to make "its mouth out of sponges."
Linux Journal has a monthly column by Marcel Gagne , called "Cooking with Linux." In the August, 2006, installment, Mr. Gagne searches "for the Ultimate Desktop Enhancements," and to this end reviews a number of applets. Only until he mentioned Beagle did I really take notice. Beagle "is a search tool that ransacks your personal information space to find whatever you're looking for," rather like Google Desktop Search, except for Linux. How exciting!
Little did I know (nor did the Beagle site mention explicitly) that Beagle essentially requires the entire Gnome 2 platform (with Mono), and that one cannot simply install the pieces that Beagle uses piecemeal. I came to realize this at about five levels deep in the dependency chain (tree would be more accurate,) after building and rebuilding about fifteen libraries, not counting those that had several incompatible versions.
After a while it became clear to me that I would have to install all of Gnome from scratch. I decided to try GARNOME. I mean, what the hell, I use Konstruct to build KDE, and that works like a charm every time. It'll be a snap, right? Wrong. It appears that the configure scripts for a number of the packages it builds are faulty. Such as with dbus, which is where my troubles began. After that point, GARNOME would periodically crap out, and I would discover that I would need to find and manually install, say, Perl::XML, or Pyrex (and I would then need to upgrade Python), or qt (which, as a KDE user, I have, but the build can't find,) or the kernel headers.
Fine. I could use a new kernel anyway, especially since at some point in this process, my CD-ROM, sound card, and USB storage devices quit working. The kernel upgrade, at least, worked the way it was supposed to and didn't crap out halfway through. Unfortunately, upon reboot, I discovered that the version of the nvidia driver I had didn't like the new version of the kernel, and since the new kernel didn't like my wireless adapter, I decided that enough was enough.
There comes a time in a Linux system's life when it becomes so full of cruft and entangled dependencies that trying to install anything results in the entire structure collapsing like a house of cards and the user has no choice but to start over. This first happened to me with Red Hat 5.2, which is why I hate RPMs. This eventually happened again with Red Hat 7.2. You would have thought I'd have learned my lesson, but I installed Fedora Core 1 after that.
Anyhow, I decided I'd install Gentoo on Sunday night, and by this afternoon my system was not only fully operational, but optimized for its hardware, with nothing nonessential installed. That is, until I finally work up the nerve to type "emerge beagle."
Make: has an article on scrounging electronic parts: "This article describes a recent scrounging project on a 3Com SuperStack II switch. This Ethernet switch was purchased to use in a home network for $10 at a Goodwill computer store. Unfortunately it was discovered later that the device had very loud fans and was actually only a 10MBit switch. Instead of just throwing it away, it was gutted for parts."
I must say that salvage is an excellent source of parts for many a project. I discovered a pile of discarded exercise entertainment systems, which yielded dozens of PICs, voltage regulators, cassette players, and most importantly, miniature LCD screens. The units as a whole appeared completely nonfunctional, but on a hunch I extracted one of the LCDs, and...
True, your friends or spouses may ridicule your penchant for bringing home "junk", may bemoan the space your collection is wasting, may plead you for the love of God to throw some of it, any of it, away. To them I say that junk is something that you throw away right before you finally need it.
I may not know art, but I know what I like:
This art project is called the ‘’215 Points of View'’ due to its
215 closed circuit surveillance cameras and 215 monitors. Its 5.5 feet
in diameter and 800 pounds of steel so you better step away no matter
how curious you are. Each monitor is showing what a camera captures on
the other side[...]
Giant Ball of Monitors and Cameras
GRC.com has an interesting utility that generates 256-bit random numbers that it displays as strings of random ASCII characters. What's so interesting about that? Well, these strings are ideal for use as passwords or encryption keys:
Every one is completely random (maximum entropy) without any pattern, and the cryptographically-strong pseudo random number generator we use guarantees that no similar strings will ever be produced again.
Also, because this page will only allow itself to be displayed over a snoop-proof and proxy-proof high-security SSL connection, and it is marked as having expired back in 1999, this page which was custom generated just now for you will not be cached or visible to anyone else.
I don't know if it's that much of an improvement over, say, "cat /dev/urandom | strings"-- but it is a bit more portable.
Remember Marble Madness ? It was an arcade game in which the player spun a trackball in order to roll a marble through a maze. The Ballbot , developed at Carnegie-Mellon, operates on a similar principle. This five foot tower of electronics can not only move by rolling its single spherical appendage, it can also balance in place.
Impressive! But it takes more than one ball to make a man. These spherical space probes could be sent to Mars or any other planet en masse, a hopping horde of silicon scientists that's unimpeded by uneven terrain.
