Hacker Friendly

After months of revisions and additions (including a complete redesign of the project website), the second English edition of Wireless Networking in the Developing World is finally ready for release!

Click through for the official press release.
Continue reading ‘Book Release: WNDW 2nd Edition’

 

Here’s a wonderful animation done to Pierre Henry’s Psyché Rock.

This is the sort of world we would have ended up with if Dali were an electrical engineer.

 

I’ve just finished watching all of Walter Lewin’s exceptional MIT course 8.02: Electricity and Magnetism. In lecture #31, he gives an hour long lecture about rainbows. I highly recommend watching it, even if you don’t have time to work through the rest of the course. You’ll learn all sorts of fascinating things about the phenomenon of the rainbow. For example, everybody knows that the colors run red-orange-yellow-green-blue-violet. But is red on the inside or the outside of the rainbow? Is this always true? Are some parts of the rainbow brighter than others? Are rainbows polarized? How big would you expect them to be? And why do they happen at all?

One particularly useful question is: where would you expect to see them when you look up at the sky? That answer is pretty easy. If the sun is out, look at your shadow. The sun should be behind you. From the shadow of your head, look up (or down) about 42 degrees. If there are fine water droplets there, then you might see a rainbow.

I was thinking about this a few days ago while standing on this corner when I happened to notice a rainbow in the sky. It was about 4:30 in the afternoon. Three things surprised me about this rainbow.

First, it wasn’t raining. But that was no problem, because there were lots of very low, very fine clouds in the sky.

Second, it wasn’t a whole rainbow, but was just a small piece of one (like a sun dog). But that might have been explained by the variable amount of water in the sky. It was, curiously enough, roughly in the shape of a rectangle.

Third, and most unsettling: it was very near the sun in the sky! I thought, “my God, physics is broken and Walter Lewin was wrong!” How could the rainbow be right next to the sun if it should be 42 degrees above my shadow, which was pointing in the opposite direction?

Obviously, I must have made a mistake, because Walter Lewin couldn’t possibly be wrong about rainbows. But there was this strange rainbow in the sky, plain as day, just to the right of the sun. So I decided to do the find-a-rainbow trick in reverse: with the rainbow to my back, I looked at where my shadow should have been (as if it were the sun) and looked up 42 degrees.

There was the space needle.

I thought, “Aha, the sun must be reflecting in one of the windows.” But the windows of the bottom half of the space needle are pointed down, not at the sky. Then I noticed that one of the windows was very shimmery, as if it was a billowing piece of bright plastic.

Then it hit me– that window was reflecting the sun, bouncing off the waves in the sound! Incredible! Physics works after all!

That also explained why there was just a rectangular sliver of a rainbow: that was the shape of the light making it.

I turned around again to examine it more closely. The colors were in the correct order (red on the outside) and it was slightly brighter on the inside of the arc. After a few moments, the rainbow suddenly disappeared. Enough time had passed that the angle of the sun had changed, and that window was no longer illuminated by the waves.

As Walter Lewin says, many people have looked at rainbows, but few people have actually seen them. I feel like I have had a chance to actually see a rainbow, thanks to an accident of the universe and a crazy Dutch mad scientist from Massachusetts. If you have any interest in electricity, magnetism, resonance, unusual optic or auditory phenomenon, or even cosmology, you will certainly enjoy MIT 8.02.

 

Check out this retro home-brew 7cm oscilloscope. It was beautifully designed and executed, down to the mahogany housing and exposed CRT.

I like this engineer’s attitude:

The choice of tubes is somewhat arbitrary. The EF91 would be very suitable in all three functions, since among small-signal pentodes, it is unusual in having suitable characteristics for providing a relatively large anode voltage swing with little distortion. But I do not find the EF91 visually attractive, so I opted for the other tubes in the main functions, relegating the ‘91 to the back of the chassis, where its smaller size fits in nicely.

If you want to build your own, he includes a schematic and parts list (at the bottom of the article).

 

This was a fun 20-minute project: A tiny Jacob’s Ladder made from an LCD backlight inverter, powered by USB. The ladder itself is made from a piece of 24AWG wire harvested from a scrap of CAT5. It makes sparks just a few millimeters wide, but they do climb very rapidly!

Rather than tempt fate and connect it directly to my laptop, I’m using a Zip-Linq AC to USB adapter. A powered USB hub would also work nicely.

Unfortunately, there just isn’t enough juice coming out of this thing to power a tiny Tesla coil… But I’m working on it.

And here’s the obligatory vid:

 

For the last several weekends, I’ve been working on building my first spark gap Tesla coil from the ground-up. After many long nights and blown capacitors, it finally worked!

This is the story of how I came to build one of these remarkable, expensive, loud, dangerous, and incomparably cool high voltage toys.

WARNING: If you find yourself bitten by the Tesla bug, you might be in a hurry to throw together some parts to see the magic lightning. You should know that there are at least a dozen ways in which you can hurt, burn, blind, deafen, or kill yourself, your friends, or your neighbors. Read all you can about Tesla coil safety before you decide whether to attempt to build one of these things for yourself. Don’t say I didn’t warn you, but feel free to tell ‘em I sent you.

Pix, movies, and more after the jump.

Continue reading ‘Tesla Coil 1.0′

 

Blistering heat. Sand storms. Vast distances. Lack of reliable power. These are just some of the challenges of operating an FM radio station in remote locations like Timbuktu. Where do you get an FM exciter that is up to the task?

Adapted Consulting has just released OpenFM: an open source 150 Watt FM transmitter specifically designed to survive the heat and grime while running on 12V solar panels.

OpenFM is a low power, affordable open source FM radio station created for use in remote areas. The system has been designed with harsh weather conditions in mind; it is able to withstand heat, dust and humidity with little manual intervention. It functions on solar power and so is particularly suited for rural environments that lack dependable electricity. OpenFM consists of a low power FM transmitter; antenna; low bandwidth, low power computer; mixing board; and open source audio software.

The construction is optimized for heat dispersion, and requires only a metal saw, drill, file, and soldering iron to build. The electronics consist of a few simple parts and off-the-shelf modules from Broadcast Warehouse. Schematics and assembly instructions are available from the project wiki, with antenna designs and more info coming soon.

 

Now here’s an industrial robot we can all enjoy. Who doesn’t like taiko?

On July 21, a team of four MOTOMAN machines — two dual-armed MOTOMAN-DIA10 robots and two MOTOMAN-HP3 welding robots — gave a special taiko performance at the nearly 400-year-old Kokura Gion Daiko Festival in Kitakyushu, which is famous for its traditional drumming competition. Organizers invited the robots to spice up the special opening ceremony for the competition’s 60th anniversary. The robots — the first ever to play taiko drums at the ancient festival — were paraded through the crowd of spectators on a float while they performed.

Here’s the vid:

Link (via Pink Tentacle)

 

I didn’t want to miss out on the iPhone media blitz, so here’s what we all really want to know about America’s favorite fanboy gadget: Will It Blend™?

 

Yesterday was 2nd annual Seattle Power Tool Race & Derby at the Georgetown block party. It was a fantastic day full of speed, danger, and grinding metal. Two 60′ tracks of plywood and two-by-fours were the proving ground for dozens of insanely creative racing machines made from modified power tools.

Hackerbot Labs entered four racers this year, including The Edger, Unicorn Offender (née Unicorn Chaser), The Green Machine, and the very popular Lady Safety. Hackerbot Labs won a coveted trophy for overall creative effort.

The main events included drag racing, tractor pull, ski-ball, stunt jumping, and smash-the-abandoned-car derby. A very good time was had by all.

Here are my photos from the event, and here are a bunch more.

UPDATE: I’ve just uploaded a video highlight. If you attended, join the YouTube group and upload your vids!