Dummy load uses gray code to adjust load in small steps

We’re not really interested in building a dummy load like this one for ourselves. But the concepts behind its design make for a nice little mental exercise as you read your way through the build description. [Pabr] wanted to build a dummy load which could be used to test a cheaply made gas generator. He wanted it to be as simple as possible, while providing a range of different loads. What he came up with is this monotonically adjustable load tester which uses gray codes for switching.

The video after the break does a good job of explaining the motivation for the design. Grey coding ensures that just one bit changes at a time. The example he uses to show the importance of this is when binary code transitions from 7 (0b0111) to 8 (0b1000). Three digits have been turned off and one has been turned on. Since he’s using light bulbs for his load this will turn off 700 Watts and then switch on 800W. That sudden jump in power draw can cause all kinds of problems with the generator’s engine. But the system he wired up will ensure that each flip of a switch moves in smaller steps.

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Light bulb efficiency exhibit updated with LED bulb option

It seems like tinkerers are always being tapped to build or repair exhibit hardware. This time around it’s [Dino’s] turn. He’s been asked to alter a light bulb efficiency demo so that it includes an LED option.

The idea here is that you crank a generator to power different types of light bulbs. There’s an ammeter built in, but possibly the best feedback is knowing how hard you have to crank to illuminate the most inefficient choice. As it stands there is a toggle switch to choose between incandescent and CFL bulbs. [Dino’s] solution is to use a three-position rotary switch. He removes the toggle switch and replaces it with a socket for the LED bulb. A new location for the rotary switch is chosen and he does a bit of work to get it mounted securely. If you haven’t worked with this type of switch before he takes the time in the video after the break to explain how they work.

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Umbrella-based windmills

[Niklas Roy] is at it again. He’s applying wind power to his projects by using umbrellas. He was inspired by the shape of an anemometer, and umbrellas turned out to be a great choice because they’re cheap and easy to find.

Anemometers measure wind speed by capturing it with egg-shaped sails (in fact, we’ve seen them built from plastic Easter eggs before). The umbrellas have a much larger area and will capture more wind. Still it’s a big jump from measuring wind speed to generating energy. That’s why he’s not trying to generate electricity, but instead using the mechanical force directly. He took a page from one of last year’s projects and used the dual umbrella setup to power a music box, thereby reinventing the wind chime. The triple-umbrella unit seen above serves as a bubble machine, driving a series of plastic rings through a soapy solution and letting the wind do the rest. We’ve embedded his demo video after the break.

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Pedal-powered 32-core ARM Linux server

Sure, it’s probably a gimmick to [Jon Masters], but we absolutely love the pedal-powered server he built using a group of ARM chips. [Jon] is an engineer at Red Hat and put together  the project in order to show off the potential of the low-power ARM offerings.

The platform is a quad-core Calxeda EnergyCore ARM SoC. Each chip draws only 5 Watts at full load, with eight chips weighing in at just 40 Watts. The circuit to power the server started as a solar charger, which was easy to convert just by transitioning from panels to a generator that works just like a bicycle trainer (the rear wheel presses against a spin wheel which drives the generator shaft).

So, the bicycle generator powers the solar charger, which is connected to an inverter that feeds a UPS. After reading the article and watching the video after the break we’re a bit confused on the actual setup. We would think that the inverter would feed the charger but that doesn’t seem to be the case here. If you can provide some clarity on how the system is connected please feel free to do so in the comments.

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UPS with dead batteries reborn as a whole-house power backup

[Woodporterhouse] must deal with regular power black outs in his area. He recently converted a rack-mount uninterruptible power supply to feed a portion of his mains wiring. This one is not to be missed, since he did such a great job on the project, and  an equally remarkable job of documenting it. It’s one of the best examples we’ve seen of how to use Imgur as a project log.

The UPS still needs to have a case, but it doesn’t need room for batteries as he’s going to use a series of high-end sealed lead-acid batteries. So he cut down the enclosure to about half of the original size. That’s it mounted just above the new batteries. For this to work you need some type of transfer switch which can automatically patch between incoming line voltage, and the battery backup. He already had one of these switches in place for use with a generator, that’s it in the upper left. The entire system powers a sub-panel responsible for his essential circuits — the electronics in the home and a few lighting circuits (we’d assume this includes utilities like the refrigerator).

One really great feature that the reused UPS brings to the project is a monitoring card with a NIC. This way he can check the server to see if the UPS is being used, and how much of the 14 battery life remains.

[Thanks Ross via Reddit]

Wind-powered POV weather station

The more we think about this one the more we like it. [Michael] built himself a wind-powered persistence-of-vision weather station. Okay, that sounds interesting, but he ups the ante when you find out what’s included in the system.

A stepper motor acts as the generator which powers the electronics. As we’ve seen before; if you spin the shaft of a stepper motor electricity is produced. [Michael] is actually spinning the housing of the motor, with the shaft mounted to the base that holds the weather station in place. This way, the electrical contacts are spinning along with the blades of the generator. By mounting all of the electronics on these blades he gets around the problem of transferring power onto a spinning platform.

A set of LEDs on the end of the blades display temperature and relative humidity readings. A hall effect sensor pulled form an old floppy drive syncs the display with the rotational speed. He’s even got a shunt system which keeps the input voltage at a safe level, and will act as a break in high winds to keep the rotors from spinning out of control. See what we mean? An interesting idea because a fantastic project when you build in features like these!

Check it out, my clothes are electric. No, seriously

Someday you may be able to use your crotch or armpits to recharge that cellphone. Heck, maybe there won’t even be a battery, just a capacitor which gets its juice from Power Felt, a fabric that converts body heat to electricity.

Now we mention the nether-regions because it’s funny, but also because it makes the most sense. Researchers have developed a fabric containing carbon nanotubes used in a way that generates electricity based on a temperature differential. We figure the areas on the body that have high heat loss would be the most efficient locations for the fabric since it is currently extremely expensive to produce (the hope is that mass-production would reduce cost by orders of magnitude). So we think battery-charging briefs are a definite possibility.

What we see here is a nano-scale Peltier electricity generator. It’s the same concept as this candle-based generator, except the increased efficiency of the Power Felt lets your wasted body heat take the place of the flame.

There’s a white paper on the topic but you can’t get at it without surrendering some [George Washingtons].

[via Reddit and Megadgets]