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June 7, 2008

Turn a Brita filter into a reusable activated carbon filter

We filter our drinking water at home, though it's not because there's a risk of giardia or heavy metals in the tap water where we live. Personally, I just like the taste of water that's been run through activated carbon. If your own water is safe from heavy metals, but you still like the way water tastes when it's been through something like a Britta filter, there's an easy way to convert the filter to be reusable, saving a ton of waste and a bit of money.

Your standard Brita pitcher filter contains two components, an ion exchange resin that is used to reduce heavy metals, and a bunch of activated carbon which is used to remove chlorine and various organic impurities that can affect the water's quality and taste. I'm not sure about how to go about recharging or replacing the ion exchange resin, but activated carbon is available in any pet store, where it is sold for aquarium water filtration.

Below is a link to an Instructable which shows you how to convert a Brita pitcher filter into a refillable carbon filter. You'll only need a couple standard tools to do the conversion, and when it's complete you'll have great tasting water, you'll be able to do refills for about 50 cents a cartridge, and you won't be tossing a one-time-use hunk of plastic in the landfill.

Refill A "Disposable" Brita Water Filter With Activated Carbon

June 6, 2008

Electronic embroidery

I'm told that one of the most popular projects at the CRAFT table at Maker Faire is our friend Becky Stern's electronic embroidery. If you're into crafting, all it takes is a little conductive thread and you can make your own fabric gadgets.

Becky posted an introduction to electronic embroidery on the CRAFT blog today and I think I just learned how to backstitch. Her introduction shows how to wire up a couple of LEDs and a switch, but there are a lot of directions to take this. Of particular interest is the LilyPad, a tiny sewable Arduino board that's about the size of a half dollar. There are also various sensors designed around this platform, including sew-friendly accelerometers. There must be a good running jacket idea in there somewhere.

Electronic Embroidery - CRAFT Video Podcast
Conductive Thread and LilyPad Components at SparkFun

June 5, 2008

DIY Slingbox

Using a standard DV cam, a Mac Mini, and the Quicktime Broadcaster utility, you can roll your own Slingbox-style TV streamer on the cheap. David Glover, realizing that his DV camera had an analog input and firewire output, put together a howto for doing just this:

Yesterday from a dusty shelf I discovered my Sony DV camera. And after playing with it for a while I discovered (or possibly re-discovered, as I might have just forgotten) that it has analogue video inputs that it will digitise and then spit out of the DV port.
So this gave me an idea - this is essentially what the Slingbox does, except the Slingbox outputs a network stream rather than DV video. But I have a Mac Mini sitting underneath my TV downstairs, and that has a DV port on it...

This is really handy if you want to catch a show on your computer while you are working from another room. Assuming you also have a DV camera and a spare Mac you can connect to your TV, it's also essentially free.

DIY Slingbox
QuickTime Broadcaster - Apple's free video transcoder and streaming utility

June 4, 2008

Use video RAM as swap in Linux

If you are into the headless or console experience, there are a couple of ways to put your machine's graphics card to good use. Most new boxes come with a GPU that has a substantial amount of RAM that is normally used for direct rendering. Using the Memory Technology Device (MTD) support in the Linux kernel, you can actually map the video card RAM to a block device and format it for swap use or as a ramdisk.

The Gentoo wiki has detailed instructions for doing this. The only tricky part is determining the video memory address, but after that it's a simple modprobe to load the MTD driver and you can run mkswap/swapon on the device just as if you were creating a normal swap disk. Considering many machines have 512MB of video RAM and it's waaaaay faster than disk, this could give you a pretty huge performance boost.

You can still use your graphics card in X, but you'll need to reserve a small chunk of that RAM for normal graphics use, use the VESA driver, and add inform the driver that it should only use that teensy portion of memory. "VideoRam 4096" in the XF86Config, for instance, will let you use your card in X and only eat the first 4MB of RAM. Everything after that 4MB is fair game for swap. Michal Schulz wrote a bit about calculating the memory address offsets to make this all work. It's the second link below, for those of you who aren't hardcore enough to deal with only the command line.

Use Memory On Video Card As Swap
Configuring X11 With A VRAM Storage Device

June 3, 2008

Google Earth has a Javascript API

Google released a plug-in, currently for Windows browsers only, that allows you to embed the Earth application inside the browser. Existing Google Maps mashups can use some of the functionality right away just by adding the G_SATELLITE_3D_MAP map type. Even more exciting is that you can interact more deeply with the map—including camera angles, KML layers, and 3D models—right from Javascript. I'm so eager to go find a PC to play around with this that I'll let the video speak for itself.

Also worth noting is that Google just released an official Maps API for Flash AS3. Call me a fanboy, but I think my head is spinning.

Google Earth API
Some Example Applications
Maps API for Flash

June 2, 2008

Wii Guitar Hero guitar as a real musical instrument

I've been trying to get better at Guitar Hero and I'm bothered by the fact that you dump so much time into learning a basically useless combination of finger twiddling tactics. At least with DDR you get some exercise, and other video games let you drive fast or kill things. Of course, I say this only because I completely fail at Guitar Hero and I'm jealous of everyone who was born with the appropriate twiddling genes that let you get past the easy level. Back to my point, though, wouldn't it be great if those gaming hours could be spent actually learning to play an instrument?

Josh Breckman posted the above video to Youtube a while ago and has gained quite a bit of notoriety for his hack that turns the Wii Guitar Hero controller into a real instrument. You don't play it like a legit guitar, of course, but by adjusting the tilt of the guitar and flexing the whammy bar, the 5 buttons can be used to toggle a variety of notes and effects.

Anyway, it turns out we get all 5 button states (obviously), up strokes and down strokes (separately), and 11 degrees of movement of the whammy bar.
I took this info and fed it into my handy synthesizer as I played and turned it into a sort of instrument. My keyboard has a pretty decent electric guitar sound, so it sounded sort of realistic. I used the wiimote's orientation and the whammy bar to add different "note banks" to let me play more than 5 notes.

I assume this is using a custom GlovePIE script to funnel commands to the software that's controlling the synth, but I don't really know much more about it than that. Josh says he'll be posting a tutorial soon. Until then, I'll be stabbing buttons while colored dots fly at me in three dimensions.

Wii Guitar Hero Synth Hack

June 1, 2008

AVR tri-color LED controller

A little while ago we posted about a fun LED scroller project made by Hackszine pal Kalanda. He wrote in today with an update about his latest howto project, a multi-color animated LED controller based on the AVR platform.

The new project based in AVR microcontrollers Its an "Habitat Mirror Hack" with RGB Leds (superflux). Its the Peggy Muppets Mirror.
I replace the regular bulbs that it has, with superflux RGB leds and i make a controller based on ATMEGA8 for control 16 rgb leds with 3 bits of color depth (8 colors). In my post you can download scheme, pcb and source code.

It looks like a fun project, and you could adapt it for other uses pretty easily. His site is in Spanish, and though I'd normally like to a Google Translate version, unfortunately Translate isn't converting the entire post, only the first paragraph. To get the full details, you'll have to cut and paste the text into Translate manually.

Thanks, Kalanda!

Kalanda's RGB Mirror: an AVR tri-color LED controller

May 31, 2008

Create a macro lens from an old 50mm

Lambert Smith has a great howto for converting a standard 50mm lens from an old SLR camera into a dedicated macro lens for your digital camera. By reversing the 50mm lens and using a number of extension tubes. The photo above is his conversion hack on a Canon Powershot G3, which has a non-interchangeable zoom lens. Custom adapters can be made by gluing filter rings back to back, so you can do this with a normal digital, a DSLR, or even a traditional film camera.

Once set up in this manner, your camera will have a fixed point of focus (unless you use a bellows). When taking a photo, you simply move the whole camera toward or away from the subject until it is in focus.

Reversed 50mm - A Dedicated Macro Lens

May 30, 2008

SafeHistory: protect your privacy from visited link analysis

A couple of days ago I wrote about the visited link javascript hack that lets any website operator query a user's browser history to determine if they've visited any other particular site. One possible use for this is to detect which Web2.0 social applications a user visits so that you can display the appropriate link badges.

It's a creepy scenario, though, that a website operator can effectively bypass the browser's intended security model to invade your privacy by seeing if you've been visiting other sites. Hackszine reader Logical Extremes commented with a solution to this problem:

This is a common phishing vector. Rather than encouraging broader use, we should be educating and protecting against it. There is a Firefox add-on that explicitly blocks this.

Some hackers over at the Stanford Computer Science Department created SafeHistory, a Firefox plugin that protects against visited link tracking techniques. It works by only allowing the a:visited property to apply to off-site links that were previously visited from the current URL.

This seems to be a reasonable way to keep the functionality of visited links without leaking any additional information. I wonder how long it will be before this is adopted as a browser behavior standard.

Stanford SafeHistory
Protecting Browser State Using Same Origin Policy (PDF)

Previously:
Detect which sites a web user visits

May 29, 2008

Wii Balance Board hacks

A few days ago, this video appeared with Matthieu Deru and Simon Bergweiler showing off a hack that allows them to surf Google Earth using a Wii. Unfortunately, there weren't too many details about how it was accomplished and I couldn't track down any source for the C# application that talks to the bluetooth device.

What I did find was this other clip from almost a month ago (?!?) in which Daniel Schneider demonstrates using the Wii Balance Board to navigate the web in Firefox.

That's right. You can actually surf the web:

He's using the latest version of GlovePIE (v0.3) to accomplish this. As far as I can tell, it's still very alpha, and the WiiLi wiki claims it's buggy, but it does appear to work. Daniel has some pointers to how he's configured things, including the Greasemonkey script that allows you to surf without clicking.

For more information on coding GlovePIE scripts that use the Balance Board, peek at the documentation.rtf file that's packaged with the GlovePIE download. There's information around page 70 that describes how the board functions and how to pull the 4 sensor values from each of its feet.

Using GlovePIE and Firefox with the Nintendo Wii Balance Board
GlovePIE

May 28, 2008

Detect which sites a web user visits

Aza Raskin's SocialHistory Javascript library allows you to do something incredibly cool: detect which sites your web users have visited on a per-user basis. The javascript runtime isn't supposed to be privy to the information in a user's browser history, but there's an information backchannel common to all major browsers which allows you to effectively interrogate the browsing history and determine if a particular URL has been visited before.

It works by creating an anchor link to the site in question and applying a CSS style to the link, specifying a different display property for "a:visited". By reading the computed style back from the anchor element, you can then determine the property's value, and consequently if the user had visited the URL or not.

This could probably be used for a number of devious purposes, but Aza's concept for the SocialHistory library is actually really useful. By querying the default URLs that belong to all the major social network sites, you can figure out which sites a particular user visits and custom tailor any social badges that you display. If they use del.icio.us, you show a del.icio.us link. If they visit Digg, you show the Digg button. It's an awesome feature made possible by a pretty freaky security leak.

Now, it's not perfect. It requires that you query the exact URLs that a user may have visited. You can't figure out everywhere they've been, how frequently, or in what order, only whether a particular URL that you know about has been visited before. On the other hand, it's a pretty useful tool considering you aren't even supposed to be able to do this.

How to Detect the Social Sites Your Visitors Use
SocialHistory.js

May 27, 2008

Conquer jet lag with a 16-hour fast

There was an interview with Clifford Saper, a professor of Neurology and Neuroscience at Harvard Medical School, in last week's Science Friday. The discussion was about a study which was just published in the journal Science about a second circadian clock in mammals that is driven by food availability. The research suggests that this second clock evolved as a sleep-cycle "reset" mechanism which allows mammals to very quickly adapt to optimize their wake period and maximize the chances of finding food during times when food is scarce.

This starvation override can take effect after only 16 hours of fasting. When the fast is cancelled by a sufficient caloric intake (read: real food), the body will shift its natural wake time to coincide with the event. So if you want to ditch your jet lag, or if you want to get up earlier in the morning, it might be as simple as fasting for the 16 hours prior to the time you would like to wake up, then eat a big meal. Your body will then override its normal light-based rhythm and wake at that same time going forward.

I'm going to give this a try. I've struggled all my life with getting up in the morning. Interestingly enough, I've also never eaten breakfast. My first meal of the day is lunch, which means I am basically fasting for over 16 every day between dinner and lunch the following afternoon. Perhaps if I skip dinner one night, eat breakfast early in the morning, and then start eating breakfast regularly, I'll turn into a morning person. I'm not really expecting results, but it's worth a try and I'll let you all know how it goes.

Science Friday: Circadian Clock Sets at Lunchtime [via ParentingSquad]

May 26, 2008

Code Kata: exercise for the software developer

It's no news that practice is the only path to being truly great at something. The art of software development is no different. The demand for programmers the way it is, however, means that a lot of folks jump into their careers head first with a certain level of formal subject knowledge, but very little practical experience. Likewise, even experienced developers are sometimes so busy that not enough time gets devoted to the practice of the craft. Dave Thomas recognized this problem and came up with a collection of short, defined practice exercises for software developers, the Code Kata:

Code Kata is an attempt to bring this element of practice to software development. A kata is an exercise in karate where you repeat a form many, many times, making little improvements in each. The intent behind code kata is similar. Each is a short exercise (perhaps 30 minutes to an hour long). Some involve programming, and can be coded in many different ways. Some are open ended, and involve thinking about the issues behind programming. These are unlikely to have a single correct answer. I add a new kata every week or so. Invest some time in your craft and try them.

Some of the example scenarios are expressed in Ruby, but aside from that they are language agnostic. What I like is that the exercises cover a wide breadth of scenarios, some of which I encounter daily in my work, and some only rarely. Even working through the problems and roughing out a solution in my head seems to be a useful tool for keeping the problem solving faculties sharp. Trying to solve problems like these involves no real deadlines or pressure, which is the necessary environment for devoting a little time regularly to focus on honing your skills.

Do you use any other resources for staying on top of your game? Let us know in the comments.

Code Kata

May 25, 2008

Polaroid emulsion lift

There's a technique called the Polaroid emulsion lift that allows you to transfer a Polaroid print to different materials, such as glass, rock, or watercolor paper. Essentially, you soak a completely dry photo (one that has set for at least 24 hours) in hot water and carefully peel the emulsion layer from the photo backing. The thin layer of film can then be carefully removed, spread over a new surface and allowed to dry.

The video above shows how the process works, and there's a link to more specific details below. This is supposed to work best with type 669 film due to it's really think emulsion layer. That said, people have had great results with other types of film, and a thinner emulsion layer will produce cool crinkly effects and tears, which can also be desirable.

Polaroid emulsion lifts
Emulsion lift example on YouTube

May 24, 2008

Colors: Nintendo DS homebrew paint application

Wired's how-to Wiki ran an article about installing homebrew apps on your Nintendo DS, describing how to install and use Colors, a really pro-looking sketch application. It seems like such a simple application, but its capabilities as a sketch tool (in the hands of someone with artistic talent) are stunning. It uses the pressure sensitivity of the DS touch screen to control the stroke width, much like how you might use an expensive Wacom tablet, except completely portable.

Running homebrew apps on your DS is about as simple as purchasing a compatible flash cartridge, so there's nothing too intimidating about using (and maybe developing) some of the great applications that are available from independent developers.

Colors!
Hack a Nintendo DS to Make an Awesome Digital Sketchbook [via LifeHacker]

May 23, 2008

Helmer render cluster: 186 Gflops in an IKEA cabinet

I usually get all excited about tiny, noiseless, low-power PC hardware, but I have to admit that this 24 core, 186 Gflop render cluster built into an IKEA Helmer cabinet is pretty inspiring. Most cool is that when it's not overburdened and jumping to swap, it's still a reasonably efficient setup for its performance specs:

The most amazing is that this machine just cost as a better standard PC, but has 24 cores that run each at 2.4 Ghz, a total of 48GB ram, and just need 400W of power!! This means that it hardly gets warm, and make less noise then my desktop pc.
Render jobs that took all night, now gets done in 10-12 min.

Janne opted for modifying the Helmer cabinet instead of using standard PC cases because the 6 cases would have cost about as much ass the motherboards and CPUs. Most of the modification involved cutting holes for airflow, power supplies, and cabling, but it looks like the Helmer's drawer dimensions accommodate the ATX motherboards almost perfectly.

I'm not all that familiar with the software behind 3D rendering (anyone care to point us to some howtos?), but Janne is using a batch management system called DrQueue that looks quite useful for a lot of distributed applications. It takes care of distributing jobs between the clsuter's nodes, allowing you to manage and monitor each of the nodes remotely from a central interface. Pretty cool stuff.

Helmer render cluster
DrQueue

May 22, 2008

Keywurl: keyword search for Safari

Keywurl is a nifty little Safari plugin that adds simple keyword search to the address bar. Say you wanted to pull up the Wikipedia entry for hacks: just type "wiki hacks" into the address bar. Looking for photos tagged with makerfaire? "flickr makerfaire" will take you to the appropriate place.

The latest beta version for Leopard allows you to right click on any form field and add a search shortcut keyword for it. This would easily let you add keywords like "hacks" or "slashdot" that would let you query for articles on your favorite sites. Unfortunately, there isn't a Tiger build of this version yet, so revision slackers like me will have to wait. You can also get at the keyword settings manually through a new button in the Safari preferences panel.

I haven't been using this long enough to tell if I'm going to keep it, but so far it's really promising. At the very least, it sends me to the right place when I type in a search term into the address bar instead of the search bar by accident.

Keywurl

May 21, 2008

Aluminum foil is a scissor sharpener

I got sucked into reading one of those 15 amazing things you never knew about aluminum foil articles. One of the claims was that you could sharpen a pair of scissors by cutting aluminum. It sounded about as plausible as mending a broken leg by driving it over with a station wagon, but I'll be damned if it doesn't work.

It's as simple as folding over a sheet of tinfoil a couple times, and then cutting it repeatedly with the dull scissors. It doesn't really grind a new edge or anything, but it has a similar effect to honing a knife edge on a steel sharpener. What's nice is that you get the honing result without needing to get a precise angle on the honing tool. The scissors push against the foil and move past it at the right cutting angle and you get a sharper edge.

I wonder if this is how the Ginsu knife could slice a tomato so darned thin after grinding on a sheet of marble and cutting through an aluminum can.

15 awesome uses for aluminum foil

May 20, 2008

Duff's Device: loop unrolling for interpreted languages

In 1983, Tom Duff invented a really strange way to use the C language's switch and case statements for the in code "unrolling" optimization of large loops. As an example, he described a simple loop that copies an array to an output register:

	send(to, from, count)
	register short *to, *from;
	register count;
	{
		do
			*to = *from++;
		while(--count>0);
	}

On every iteration of the loop, in addition to the copy that is being performed, the count variable is decremented and a comparison is done against 0. Duff's Device allows you to achieve the same result, but with only an 8th of the overhead:

	send(to, from, count)
	register short *to, *from;
	register count;
	{
		register n=(count+7)/8;
		switch(count%8){
		case 0:	do{	*to = *from++;
		case 7:		*to = *from++;
		case 6:		*to = *from++;
		case 5:		*to = *from++;
		case 4:		*to = *from++;
		case 3:		*to = *from++;
		case 2:		*to = *from++;
		case 1:		*to = *from++;
			}while(--n>0);
		}
	}

What happens is that the loop is unrolled 8 times, so each iteration of the loop runs the internal code 8 times over without the comparison. The genius of Duff's Device is that it takes advantage of the way the C switch/case structure works. The first time through, if the iterations don't divide evenly by 8, the loop code is executed enough times to equal the remainder of iterations/8. It's a little bizarre, because the "do" statement occurs within the switch, but there are "case" statements within the "do". Nevertheless, it's valid C.

Before someone cries foul, remember that this is only really suitable for speeding up the performance of inner loops when no suitable, better algorithm is available. If you code C, most modern compilers are smart enough to automatically optimize your code and unroll loops for you.

For interpreted languages like PHP or Javascript, however, you sometimes need to do a little optimization on your own if you want to squeeze out some extra performance. Luckily, both languages have a c-style switch statement.

Andy King wrote about a slightly altered version of this loop unrolling algorithm which ditches the switch statement and breaks the normal Duff's Device into two separate loops, one for the remainder and one for the unrolling. In Javascript, it performs a simple addition loop in only a third of the time of a normal for loop (testVal++ is the normal loop's interior):

function duffFasterLoop8(iterations) {
  var testVal=0;	
  var n = iterations % 8;
  if (n>0) {
    do 
    {
      testVal++;
    }
    while (--n); // n must be greater than 0 here
  }
    
  n = parseInt(iterations / 8);
  do 
  {
    testVal++;
    testVal++;
    testVal++;
    testVal++;
    testVal++;
    testVal++;
    testVal++;
    testVal++;
  }
  while (--n);
}

It's not as syntactically clever as Duff's Device, but it's a good way to manually unroll an inner loop and get the best performance for your extra effort.

Duff's Device
Andy King's Optimizing JavaScript For Execution Speed

May 19, 2008

Flying bike for Google Earth

"Some guy who's never met Mike" wrote in to tell us about Mike's Flying Bike, a completely unconventional flight-sim interface created from a bicycle, a Sun SPOT sensor/microcontroller, and Google Earth.

So, you pedal this stationary bike to pick up speed and take off. Then you manipulate various hand levers and the handlebars to affect the elevator, aileron and rudder controls. It's never been so fun to fly around the Earth. In your living room. On a bike.

Mike's Flying Bike for Google Earth