Come out to ADX this Saturday (December 17, 2011), from 11am to 5pm, and load up on great gifts. ShareBrained will be there, along with friends Curious Terrain and Platemark X.

Alternative time-telling devices are compelling, but only if they’re easy to read. Building a kit can be satisfying, but only if it leaves room for creativity. The Chronulator clock kit fits the bill on both counts.

Check out the Ultimate Kit Guide online, or buy a paper copy at your nearest magazine vendor.

For completeness, I also uploaded the older TI MSP430 Chronulator 1.3 implementation. If you bought a Chronulator kit before November 2008, this is the code you want.

The NOAA-19 APT signal is a relatively simple signal to understand. When the satellite captures an image, it scans through it line-by-line, at a rate of two lines per second. The brightness of the image during scanning is amplitude modulated on to a 2.4kHz carrier tone, and sounds like this:

You can hear the (slightly painful) 2.4kHz carrier tone. Also notice the tick-tock-tick-tock pulse of the signal. Each tick and tock is a sync signal followed by a line of image data. Why a tick *and* a tock? APT transmits *two* images at a time, so the “tock” is the sync signal between data from the first and second images.

I rigged up a GNU Radio Companion “patch” to demodulate the APT signal. It’s based off a APT decoder by Alexandru Csete. It filters and demodulates the signal and outputs a file of demodulated data.

I tweaked the demodulated file a bit with Python, normalizing the data to the range (0,255) and writing out a byte-per-sample file:

import numpy
raw = numpy.fromfile('words.f32', dtype=numpy.float32)
normalized = raw / max(raw) * 255.0
output_u8 = numpy.array(normalized, dtype=numpy.uint8)
output_u8.tofile('pixels.u8')

Following Alexandru’s lead, I used ImageMagick’s “convert” to translate the byte-samples to a PNG image:

convert -size 2080x1194 -depth 8 gray:pixels.u8 image.png

And behold! A really noisy satellite image!

There are two images visible, side-by-side. The left side seems to be a visible spectrum image, while the right seems to be infrared. You can see parts of California, Oregon, and Washington. The Columbia River, a few miles from my house, is somewhat visible, too:

This was my first attempt at capturing a satellite signal, so I was using a crappy all-purpose dipole antenna. Hence the wretched amount of noise. But still, for my first attempt, I’m pretty pleased! Now, to build a better antenna…

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You may wonder where I’m going to take ShareBrained. Right now, I’m really in to these things:

• Audio projects — new musical instrument interfaces and synthesis platforms.
• Software radio projects — agile radio transceivers and spectrum analyzers.
• Open technical tools — JTAG and Serial Wire Debug interfaces, logic analyzers, oscilloscopes.
• Cool and hackable timekeeping devices like The Chronulator

As I get more in to these projects, I’ll post them here on the blog. I look forward to all your comments, suggestions, and contributions.

Wish me luck!

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Summer 2009, I attended the first “hacker” camp in the United States, ToorCamp. It was a spectacular experience to be among so many wickedly-smart people who are curious about technology’s implications for society. The scenery was amazing (a Titan missile silo in Eastern Washington State), and I made several friends who are goading me to work on new projects.

Ham radio is an old interest of mine. Maybe ten years ago, I got a radio receiver and explored the radio spectrum — listening to airplanes, pagers, cabbies, and cordless phones. I was shocked to learn that radio communication is far less private and secure than we realize. This was driven home quite forcefully by Michael Ossmann and Dominic Spill‘s talk at ToorCamp, where they demonstrated sniffing Bluetooth keyboard keystrokes with a software-defined radio. After that, I had to have a software-defined radio of my own to experiment with, so I started developing various elements as separate circuit boards. Here is a picture of a PLL+VCO board I put together, using some nifty prototyping techniques (which I promise to blog about soon).

As for my day-job, I’m now designing electronic toys. I’m learning a lot about how to design and produce electronic products inexpensively and on a large scale, which I’m sure will come in handy for ShareBrained stuff. I’ve also been bitten by the 32-bit microcontroller bug, and would like to make all my future microcontroller projects ARM-based.

This year, I got into auto racing, which I suppose was inevitable considering my upbringing. As a child, a lot of my weekends were spent with my family, camping at race tracks and helping my dad race one Fiat or another. It was great fun, but by the time I was old enough to race, it was simply too expensive to do so competitively. So I never seriously considered it. I did, however, help out my dad periodically with his ongoing racing activities. For instance, last year he fell in with a crowd of stock car racers who wanted to enter a big-ass Dodge in the 25 Hours of Thunderhill. I went along to help do tire changes and keep tabs on our lap times. Our experience was less than stellar. Despite several heroic repair efforts, we couldn’t keep up with all the ways the car broke, and packed it in only 90 minutes into the race.

Regardless, the die was cast, and I was thinking of how I could get into a car and go fast. Fortunately, an affordable solution had presented itself a few weeks earlier. I’d attended the first-ever ChumpCar race at Portland International Raceway, which took place on Halloween. The defining feature of ChumpCar? Cars must be worth no more than $500 (not including safety equipment). My dad introduced me to a guy he knew who was looking for drivers for his ChumpCar team. Before I knew it, I was on a team of six drivers taking a Mazda Miata to a 24-hour race in Spokane, Washington.

Like the Thunderhill race, things didn’t turn out too well. Overnight, the car met a concrete barrier twice, and twice, the crew rebuilt the car and got it back on to the track. Then, as the sun came up, the engine came apart (unhappy valves). We parked the car six hours from the end of the race, then limped it across the finish line. Still, it was insanely fun.

Naturally, with such a dismal showing, I had to try again. So I signed up for the Portland race *this* Halloween. Things went far better! The car, in a ravishing new pink color scheme, ran well and our drivers avoided the concrete walls. I got to drive in traffic that was reminiscent of Bay Area traffic (70+ cars on a two-mile track). Madness!

You may reasonably conclude that ShareBrained will take a turn into software-defined radio and automotive telemetry projects. That’s not to say the Chronulator is going away. In fact, with my new ARM microcontroller skills, I’m thinking about a mega-Chronulator…

If you haven’t been following this project, the idea is simple. You’re at Maker Faire. You’ve never seen Make: TV before. You have a USB drive in your pocket. You walk up to our quaint, blinking machine, plug in your USB drive, choose an episode of Make: TV, and download it to your USB drive so you can take it home and watch it.

Here I am demonstrating it, appropriately enough, to John Park, the host of Make: TV.

And here’s an assemblage of video I shot of people using the dispenser.

We were still putting on finishing touches and tweaking code a couple hours into the first day of the expo, but once we got the kinks worked out, it hummed along nicely. About five percent of visitors had problems with our machine. We identified two circumstances: NTFS- or HFS-formatted drives, and FAT32 drives that appeared to have no partition table. If we do this again next year (if Make: TV Season 2 gets funded), we’ll definitely try to solve these shortcomings for in Dispenser 2.0!

Thanks to Nick at Twin-Cities Public Television for his support on this project. Thanks to Brian for his help coding the software. Thanks to Don and Jason of Dorkbot PDX for their ideas and material/moral support. Thanks to James Provost for whipping up some graphics on super-short notice. Thanks to my wife for her user interaction suggestions (many of which I stubbornly ignored at my peril). And thanks to my dad for his woodworking help and various material contributions.
]]> http://www.sharebrained.com/2009/06/09/make-tv-dispenser-2009/feed/ 2 http://www.sharebrained.com/2009/06/09/make-18-review-chronulator/?utm_source=rss&utm_medium=rss&utm_campaign=make-18-review-chronulator http://www.sharebrained.com/2009/06/09/make-18-review-chronulator/#comments Wed, 10 Jun 2009 05:03:42 +0000 jboone http://www.sharebrained.com/?p=226 Continue reading →]]> Well, my last post about Make Magazine turned out to be premature. The review of the Chronulator, slated for volume 17, was bumped due to space constraints. But in the latest issue, Make Volume 18, there is now a Chronulator review! You can find the review in the Toolbox section, page 159, titled “Like Clockwork”.

John Park, the host of Make: TV did the honors, and really dug the kit. Sadly, his most excellent Chronulieta cigar-box Chronulator, which he built for the review, was not pictured.

One editorial comment: I must defend my engineering prowess by mentioning that the Chronulator consumes 200 microamps, not 200 milliamps as the review states. At 200 microamps, that’s more than a year on two AA batteries!

The process has been slow-going. It took a while to design the user interface (big push buttons!), design a control circuit board, and set up a little Linux computer to run it all. Last weekend, we finally got to the step of building the cabinet. It doesn’t look like much yet, but just wait…

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