Who needs a tactile interface when you can wave your hands in the air to make music? Air String makes that possible and surprisingly it does so without the use of a Kinect sensor.

In the image above, you can see that two green marker caps are used as plectra to draw music out of the non-existent strings. Judiciously perched atop that Analysis and Design of Digital Systems with VHDL textbook is a camcorder recording an image of the player. This signal is processed by an FPGA (hence the textbook) in real-time, and shown on the monitor seen to the right. A set of guides are overlaid on the image, so the player knows where to pluck to get the notes she is expecting.

The program is designed to pick up on bright green colors as the inputs. It works like a charm as you can see in the video after the break. The team of Cornell students responsible for the project also mention a few possible improvements like adding a distance sensor (ultrasonic rangefinder?) so that depth can be used for the dynamics of the sound.

Sometimes you don’t need a lot of horsepower to win a speed record. In a fluke of no one else competing in the alt fuel class,  [John]‘s biodiesel motorcycle set a new land speed record at the LTA event last summer.

[John]‘s bike is a junkyard 1978 Kawasaki KZ400. The stock engine was replaced with a Chinese knock off of a Yanmar air-cooled diesel motor. The fuel is regular old vegetable oil. From the looks of the exhaust, we’re assuming [John]‘s garage has a rich french fry smell to it.

Compared to highway speeds, [John]‘s runs for a land speed record are a little absurd – a nice bonus when you’re the only driver in your class. The first pass of 42 mph was a little disappointing, so [John] removed the fender, tail light and brakes. After all the unnecessary weight was removed, the top speed – and new record – was 56.5 mph.

Converting a diesel car to run on french fry oil is great and a lot better for the environment than burning liquefied dinosaurs. In any event, a green motorcycle is a lot better than 2000 pounds of automobile moving less than 200 pounds of person. Check out a few of [John]‘s land speed runs after the break.

Sometimes, changing one little bit of a green hack turns it into a build that wastes as much energy as our gaming rig. [Dr. West]‘s automatic window controller is one of these builds. The good news is the window controller can be easily modified to cut energy costs in the fall and spring.

[Dr. West] doesn’t have any control over the heat in his apartment and for the entire Canadian winter, his apartment gets really hot. He doesn’t pay for his heat, so he does what any of us would do – crack a window. Inspired by this post, he put a linear actuator in the frame of his kitchen window. [Dr. West] didn’t want to damage the window frame, so he attached the actuator to a piece of square aluminum tubing that mounts to the existing screw holes.

The electronics, [Dr. West] used a Rabbit 2000 dev board, LCD display and keypad, and built an H-bridge circuit on a bit of breadboard. Because of a port conflict and admitted laziness, an Arduino is used to read the thermistor. The display shows the current and desired temperature, and the Rabbit opens and closes the window accordingly. All the source code is posted in the forum post.

While it’s not the most ‘green’ idea to dump heat from a building’s HVAC system out into a frozen tundra, this would be a great build to automatically open and close windows in the more temperate seasons. Open windows during the day, close them at night and you’ll have no more problems coming home to a house that’s either too hot or too cold. Check out a video of the automatic window after the break.

Most everyone is looking to live a little greener these days, with motivating factors typically being the preservation of the environment or financial considerations. [Fabien] fit into the latter category after realizing that about 25% of his monthly gas bill went to heating the water he and his family use each day. After a few calculations, he found that they only required hot water 68 of the 168 hours per week that the water heater was typically running. He figured the best way to save a few dollars was to rig the water heater to turn itself down when it wasn’t being used.

He connected a servo to the temperature control knob on his water heater, allowing it to be adjusted by a microcontroller. Having a rough idea as to the schedule his family keeps during an average week, he wrote an application for his Netduino that would actuate the servo when needed. A DS1307 real-time clock was wired to the Netduino for accurate timekeeping, so as to ensure [Fabien's] wife never had to endure a cold shower.

It’s a shame that most water heaters don’t ship with some sort of programmable thermostat like you see with newer HVAC systems, but this hack is definitely a step in the right direction.

Continue reading to see his power-saving water heater in action.

Amidst the noise of a bazillion robots and Tesla coils at the 2010 Bay Area Maker Faire, we located a bubble of usable WiFi, and got a nearby power charge to boot. If nothing else here, we want this:

The SolarPump Charging Station is a self-contained oasis of free power for laptops, cel phones and even electric bikes. This charging station is one of several designs created by Sol Design Labs of sunny Austin, Texas. No bigger than a bus stop (and way cooler looking), it’s like the ultimate case mod, repurposing a vintage Citgo gas pump and recycled metals for more modern needs. Three large Sanyo solar panels provide power for devices and shade for users, while topping off the internal 24V 100AH battery for nighttime use (with LED lighting) or cloudy days. The end result transcends “green” — the SolarPump is simply appealing at a visceral level, managing to be simultaneously fun, attractive and practical. Did we mention wanting one? We totally want one.

[Rp181] is at it again with version 2 of his rail gun project. The original did have some power with 18 400V 3900uf capacitors, but he’s ramped it up to now using 40! Reaching more than double the amount of joules of energy, 12kJ vs. the 5.6kJ! Some other changes include a new injector solenoid setup and revision 3 of his breakwire chronograph. Sadly, he doesn’t mention if this is as green as his first rail gun. Check out a video of just the injector firing and an animation explaining some new updates after the jump.

[bongodrummer] wanted to use a lathe to make some gifts for his family. Instead of buying one, he decided to make one and recycle some parts in the process. More info after the break.

[bongodrummer] scavenged a motor from a washing machine which is a great choice because these motors are capable of generating plenty of torque. To control the speed of the lathe he developed his own pulse width modulation controller. All of the parts were then mounted to some heavy steel plates and an enclosure was built around the belt-driven assembly. In keeping with his recycling goals, the tool rest was fabricated from tubing reclaimed from a junked bicycle frame.

This lathe is not a CNC machine, but judging from the wooden bowl he turned out we’d say this project is a huge success.

Sometimes we need someone like [FireMyLaser] to show us that you really don’t need things like custom PCB’s, expensive tools, or laser cutters to pull of a hack. His laser spiro subsists mostly of  toothpicks, hotglue, and determination. It is a two motor spiro with a base motor and a motor mounted in a  spinning cage. The cage gets power through brushes much like other projects we’ve covered. See a video of it in action after the break.

[thanks pseudolobster]

[bugloaf] tipped us off about this flower power hack. University of Washington researchers, [Babak], [Brian], and [Carlton] have developed very low power circuits to run directly off of trees. This builds upon the work of MIT researchers and Voltree Power. A voltage of up to around 200mV is generated between an electrode in a tree and an electrode in the ground. Identical metals can be used as electrodes as the process is not like that of a lemon or potato battery. The significant development here is the use of a boost converter and exceptionally low power circuits. What kind of applications can you come up with for this source of power? Maybe you could try to combine this power with the power from donuts and hair.

We’ve already covered a pipe bomb mini-fridge this week, but inventor [Tom Chalko] provides us with today’s fridge hack. He noticed that chest-style (laying down, see above) freezers were more energy efficient when compared to normal stand up refrigerators at the same size, despite the colder temperatures involved. This is largely due to the fact that these chest-style freezers keep cold air in like water in a bowl, even if the lid is open. He has written a very thorough report on his findings (pdf), as well as a detailed walk through of the manageable task of converting a chest-style freezer into a chest-style fridge. In the end, his fridge only used 103 Wh of electricity on the first day to reach and maintain between 4° and 7° C (39° to 45° F), and he noted that 30% of that was just getting it up to temperature. After that, the fridge only turned on for roughly 90 seconds an hour, making it a very quiet fridge as well.

[Mike] really liked the thought of the Monome, especially the green aspect of their construction. He felt he could take it a step further. After 40 years of electronics tinkering, he had quite a spare parts box. He constructed his monome clone from stuff he just had laying around.  All of his pieces were either rejected samples from his company or outdated parts destined for the trash bin. Great job [Mike]. If you are planning to build one and don’t have the buttons laying around, you can get a more typical monome look and feel by going with the sparkfun RGB pads, like we did back in March.

[via Makezine]

[Roland] recently graduated from UC Berkely. For his graduation ceremony, he wanted to do something unique. He built a diorama on his graduation cap depicting a house driven from alternative energy. The whole thing is solar powered. The wind turbine is actually powered from the solar panel, and with a remote control, he can make the sun rise and set.

Recycling is great. We’ve seen a pretty hard push in that direction recently. We like the fact that our modifying of hardware is generally saving it from the dump. Keep in mind, that just using old hardware can be advantageous too. We don’t always need the new shiny thing, maybe we’re fine with what we’ve got. That is exactly what lastyearsmodel.org is about. You can join their facebook group and even get stickers for your old devices.

[Murray484] submitted his instructable on how to create a stepper motor controller from an old scanner. He removed the motor and controller from an old scanner then harvested the parts. He’s pretty much starting over, taking the ULN2003 chip from the scanner motor controller and putting it on a fresh board. He then wired it all up, installed the software and got it working. Finally, he built a container out of cardboard for it all. Though he could have made it nicer looking and used higher quality building materials, he was trying to make this a “green” project for the epilog laser cutter contest. He’s done a good job recycling, this could be pretty useful.

You probably saw [Phillip Torrone] and [Limor Fried]‘s twittering Kill A Watt earlier this week. It was an entry in the Core77/Greener Gadgets Design Competition. We saw a little bit about how it was assembled, but now they’ve posted a full guide to assembling the hardware. Each Kill A Watt gets an XBee radio that transmits back to a receiver that logs the power usage. The difficult part when putting this design together was the XBee required 50mA when transmitting. This is well above the Kill A Watt’s internal power supply. They remedied this by adding a 10,000uF supercap to act as a rechargeable battery. The daily twittering is just a side-effect of the project. The Kill A Watts transmit every 2 seconds, so you’ll get a very accurate report of your power usage. This is a great project for renters who can’t permanently modify their power infrastructure. Each Kill A Watt can support quite a few appliances since they’re rated for 15A, ~1800W.