brainwagon

Over sushi this evening, Tom mentioned “Chua’s circuit”, or “Chua’s oscillator”. I knew that I had seen this somewhere before, but failed to remember that Chua was also the guy who first theorized about the memrister: a circuit element whose resistance is proportional to the sum of the charges that has been passed through it. […]

I’ve been working on a script or two for generating intros for some of my little YouTube videos, and thought that maybe something like an animation of the Lorenz strange attractor might make a somewhat interesting background. A little tweaking, and I produced the following example (only 10 seconds long, and with some Morse as […]

I’ll just lead off with a picture: This is a graph of the so-called “Lorenz attractor”, first described by mathematician Edward Lorenz in his paper Deterministic Nonperiodic Flow back in 1962. I learned about this kind of stuff probably back in highschool by reading Scientific American. Anyway, the equations themselves are pretty simple, but describe […]

Antenna design and manufacture has historically been pretty, well, primitive. There are reasons for this: early on, solving the large systems of equations to adequately model complex antennas was difficult. Luckily, advances in computers and software make that much more tractable. Now, we can design antennas with dozens or even hundreds of elements, and in […]

A bit more digging on yesterday’s topic (crystal microphones) yielded this book, published by the U.S. Army, entitled CW and AM transmitters and receivers which included some additional useful information regarding the construction of crystal microphones.

I’ve always been interested in crystals: their outer beauty hints at a certain kind of inner beauty, caused by the orderly arrangement of molecules at the atomic level. When I was a kid, I made crystals from sugar, salt, alum, and copper sulfate, but never tried Rochelle salts. Rochelle salts are interesting because they are […]

Carmen and I just got back from a trip to London, and we had a blast. One of the geekiest things we did while there was to take a day trip by train out to Bletchley Park to see the site of the codebreaking efforts by the British during WWII. As any long time reader […]

Having completed my posting of a new program in celebration of pi day (going back to just spelling it out, since somewhere in the WordPress to Twitter chain, the HTML entities get dropped) I was reading my twitter feed, and found Vi Hart’s amusing video asserting that “Pi is Wrong”. Click through and watch the […]

It’s 3/14 again, and that means that it’s π day! Huzzah. This year, I thought I’d try implementing a way of computing π which was entirely new to me: finding π hiding inside the Mandelbrot set. David Boll made a posting back in 1991 to sci.math: I posted this to alt.fractals about a month ago, […]

Scanning some of the usual RSS feeds, I saw this link to an interesting little laser paper cutter project, driven by Arduinos and a couple of EasyDriver stepper motor boards, and uses parts salvaged from a DVD-R board: Pocket laser engraver. Not as useful as full fledged laser cutter, but a neat project nonetheless.

Here’s an interesting project: a tube based regenerative receiver that uses an LM386 as an audio amplifier. Wacky. Still, it appears to only use 12v supplies, which may make it a fun and interesting project. The “Speaky” HF SSB transceiver and other homebrew projects: Tube/Valve receiver… the schematic Addendum: Apparently this YouTube video served as […]

I’ve been pondering a couple of projects that could benefit from having custom PCBs manufactured, and David Jones twittered about one I hadn’t seen before: Open PCB Prices seem very good, and you can also order some pre-designed open source boards for very modest prices. I’ll check it out more later.

A couple of weeks ago, I blogged that a group of students were planning to photograph the final launch of the shuttle Discovery from a high altitude balloon. What’s remarkable is that they succeeded. Click the link and surf on over to find what a couple of Android phones can do at 100K feet.

Okay, I’ve been thinking (somewhat abstractly, since I have had relatively little free time lately) about what I eventually want my beacon transmitter to be. One of the issues with it is that I’d like it to be relatively autonomous and lower power: I’d like it to be able to run for weeks at a […]

My experimentation with oscilloscope displays made me wonder what the oscilloscope clock by Sparkfun/Dutchtronix used. It turns out to be a $5 dual parallel input DAC from Analog Devices, even available as a 20 pin PDIP. It can apparently do 833K samples per second, making it quite a bit faster than a conventional sound card […]