Make A Cardboard Bookshelf In Less Than A Day

July 27, 2012 by Mike Szczys 8 Comments

Lucas came up with a real winner when upcycling cardboard to use as a bookshelf. It’s visually pleasing, can be built basically for the cost of glue and a mounting brackets, and you don’t have to feel bad if you decide to get rid of it later on.

What he saved in raw material cost he spent in labor. There are 23 different layers of cardboard that went into the project, not including the spacer squares between each piece. The vast majority of the time spent in the clip after the break shows a fast-time video of him cutting out the layers. It apparently took about eight hours of cutting, and we’d image he’s got a claw of a hand after all of that work.

This is hanging from a single L bracket positioned in the square opening with two nails to keep it level. We’d suggest including a better mounting technique in your design. If you have some ideas about this please let us know in the comments.

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Driving Your Home Appliances With Hybrid Power

July 22, 2012 by Mike Szczys 19 Comments

This system of hybridizing your home’s electric appliances is an interesting take on solar energy. It focuses on seamlessly switching appliances from the grid to stored solar energy as frequently as possible. There’s a promo video after the break that explains the setup, but here’s the gist of it.

Follow along on the pictograph above. We start on the left with solar panel. This feeds to a charger that tops off a 12V battery. When that battery is full, the charger feeds to the inverter which converts the 12V DC to 110V AC power. This is fed to a pass-through which is in between the appliance (in this a case a lamp) and the wall outlet. The pass-through will switch between mains power coming from the outlet, and the 110 coming from the inverter. The homeowner won’t know, or care, which power source is being used. But sunny months should result in lower energy bills. The real question is how long it takes to cover the cost of the system in saved electricity.

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Monitoring Your Home Energy Use

July 18, 2012 by Mike Szczys 19 Comments

[Dave’s] been elbow-deep in mains voltage while building this home energy monitoring rig. He started with an approach that is different from most we’ve seen before. He wanted a system that could make a linear measurement to keep the accuracy as high as possible. His first thought was to use a opto-isolated linear amplifier to measure voltage, but ended up altering that plan since he’s looking for digital values when all is said and done.

He’s using an ADC on the mains side of the interface board, then sending the digital values to an Arduino with opto-isolators to keep the high voltage separate from the low. This does complicate things a little bit, as he has low voltage rails on either side; 0V and 5V to run the ADC on the mains side, and separate 0V and 5V to run the Arduino. To solve the problem of accurate current measurement over the full range a house uses he opted for a Programmable Gain Amplifier. It’s addressed via SPI and allows him to adjust resolution to facilitate accurate measurement of very small currents. We think anyone who has tried to measure small appliances (like an alarm clock) with a Kill-A-Watt and gets a zero reading will appreciate this.

The Arduino sends data via a serial connection, which [Dave] is currently graphing using his laptop. It would be nice to see a simple web-server using the Ethernet shield (or a different board like the RPi) so you could log in from the couch and see what’s been going on with your home grid.

Solar Oven Built To Last

July 11, 2012 by Mike Szczys 18 Comments

The problem with most solar ovens is that they’re flimsy builds that will stand up to only a handful of uses. But this one stands apart from that stereotype. It’s big, sturdy, and used a lot of math to efficiently gather the sun’s energy when cooking food.

This is the third version of the build and each has included many improvements. The obvious change here is a move from aluminum reflectors to actual mirror reflectors. These attach at a carefully calculated angle to get the most power from the rays they are redirecting. The orange mounting brackets for the mirrors also serve as a storage area for transport. The rectangular reflectors fit perfectly between them (stacked on top of the tempered glass that makes up the transparent side of the cooking chamber).

The body of the oven doesn’t track the sun and one of the future improvements mentions adding tilt functionality to the base. We’d suggest taking a look at some of the solar tracking setups used for PV arrays.

[Thanks John]

Pedal-powered 32-core ARM Linux Server

July 9, 2012 by Mike Szczys 12 Comments

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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LiPo Battery Tester For Solar Vehicle Battery Array

June 27, 2012 by Mike Szczys 12 Comments

If you’re building solar vehicles at a competitive level you’ve got to know exactly how the storage batteries will perform. To that end [Matthew] built a Lithium Polymer battery tester for use by the McMaster University Solar Car Project. It worked well, but could only test one battery at a time. He just finished up a second version, which can test battery specifications on up to eight units at once. It saves a lot of time, but still takes fifteen hours to test just one set of the units used by the vehicle.

The most important aspect being measured is the discharge curve. Sure, there’s a datasheet that includes this information, but how can be sure that what you received will perform at spec? Each of the eight channels can be disconnected from the system using a relay. This is just one of the safety features which watch for things like over-voltage and over-current conditions. Remember, Lithium batteries can heat up fast if there’s a problem. Data is sampled on a 12-bit ADC and can be pushed to a computer via USB for graphing.

Urban Farming Uses Aquaponics To Make Farmland Where There Is None

June 27, 2012 by Mike Szczys 47 Comments

[Eric Maundu] is farming in Oakland. There are no open fields in this concrete jungle, and even if there were the soil in his part of town is contaminated and not a suitable place in which to grow food. But he’s not using farming methods of old. In fact farmers of a century ago wouldn’t recognize anything he’s doing. His technique uses fish, circulated water, and gravel to grow vegetables in whatever space he can find; a farming method called aquaponics.

The video after the break gives an excellent look at his farm. The two main parts of the system are a large water trough where fish live, and a raised bed of gravel where the fish waste in the water is filtered out and composted by bacteria to becomes food for the vegetables. More parts can be added into the mix. For instance, once the water has been filtered by the stone bed it can be gravity fed into another vessel which is being used to grow lettuce suspended by floating foam board. But the water always ends up back in the fish trough where it can be reused. This ends up saving anywhere from 90-98% of the water used in normal farming.

But [Eric] is also interested in adding some automation. About seven minutes into the video we get a look at the control systems he’s working on with the help of Arduino and other hardware.

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