Solar Hot Dog Cooker Does it With Parabolic Mirrors


For a university project [Adam Libert] decided to make his very own parabolic hot dog cooker. Now, we must say, this is a project that could probably be cobbled together in a weekend from scraps, but since it was for a lab, [Adam] decided to go all out – complete with a perfect laser cut frame.

The objective of the lab was to design a project that can use solar radiation to accomplish a task, and being partial to hot dogs, the hot dog cooker was a natural choice. He designed the parabolic mirror to focus 1/5th of a square meter of sunlight directly at a hot dog. To do this, he laser cut the frame out of MDF, and using tinfoil, toothpicks, and poster paper, assembled the mirror. The whole thing cost less than $5 (ignoring laser time) and can be setup in a matter of minutes.

He determined the heat output of the cooker to be around 10W at the hot dog, which means he was able to bring the hot dog to 150°F in about 10 minutes — which was surprisingly close to his original calculations, because let’s face it, tin foil is hardly an ideal mirror.

Interested in other solar cookers? Why not cover a satellite dish in foil tape? Or if you want a quicker-cooked-hot-dog, why not plug it directly into the wall?

Roll your own parabolic microphone

Parabolic microphones are used to listen in from a distance. You see them on the sidelines of NFL football games, but they’re part of the standard issue in detective and spy novels. Now you can build your own parabolic microphone by following this example.

The one component that may be hard to find is the parabolic reflector. You cannot simply use a bowl or other curved object as the precise parabolic shape ensures that sound waves are reflected onto one finite focal point. For this build the reflector was obtained from an eBay seller. But the other parts are scavenged from easy to find sources. The microphone itself is an inexpensive element from Radioshack. It is mounted in the shell from a tweeter speaker, which helps to gather the sound if the element isn’t exactly aligned with the focal point. The setup also needs a preamplification system, which uses many components. Luckily there’s a schematic and other reference material linked in the write up.

You can also build a laser microphone which detects sound waves on a pane of glass.

[Thanks Anonymous]

FabLab helps the developing world set up long-distance wireless Ethernet

The wooden frame seen above hosts a parabolic reflector making up one side of a wireless network link. This is a Fab Lab project called FabFi which uses common networking hardware to setup long-distance wireless Ethernet connections. It’s a bit hard to tell in the image above, but the reflector focuses radio waves on the antennae of a router we’re quite familiar with, the Linksys WRT54G. It’s held upside-down in an enclosure meant to protect it from the elements. The node above manages to complete a connection spanning 2.41 miles!

One of the core values of the project is to develop hardware that is easy to build with limited resources, then to make that knowledge freely available. Anyone who has the ability to download and print out the 2D design file can build a reflector for themselves. As we’ve seen in other projects, paper stencils and hand tools can handle this job with no need for a laser-cutter (which was used for the prototype). WRT54G routers are inexpensive and the project uses the open source firmware OpenWRT. They can be run from 12VDC power which means a car battery works when mains power is not an option. The system has been running in Afghanistan for two years and hardware failure is still in the low single-digits.

[Thanks das_coach]

Various Cantenna builds


Here is a classic project used to increase wireless signal strength. Cantennas focus using a waveguide very much like a magnifying glass focuses light. [Robert] made a Natural Light beer cantenna, pictured in the upper left. His approach used three beer cans, a paper towel holder, and a shower curtain rod. On the tipline, he noted a signal boost from 11Mbps to 54Mbps. This is certainly something we can hack together if our room lacks adequate signal. Read about parabolic and seeking versions after the break.

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