Just like destroying an ant colony with a magnifying glass, there’s nothing like cooking hot dogs and roasting marshmallows with a nice parabolic reflector. Of course covering an old satellite dish with mylar or aluminum tape doesn’t take much skill, however cool it is. [Uwe] came up with a much more technical means of building a Fresnel reflector that will cook your hot dogs in seconds, but only on sunny days.

[Uwe] channeled a little bit of [Apollonius] when he realized that a flat cardboard ring with a section removed could be joined together into a conic section. The resulting section looks just like one concentric ring in a Fresnel reflector. [Uwe] wrote a small program in Visual Basic to calculate the necessary diameter and angle of his conic sections.

A bit of cardboard was cut out and pieced together with some very reflective aluminum tape. The resulting Fresnel reflector concentrates 117 times the normal solar radiation onto a small point. It’s more than enough to burn holes in construction paper, but we’ll be using a microwave for our lunch today.

[Johnie] built himself a CNC woodburner powered by the sun. Like the solar 3D printer we saw last summer, [Johnie]‘s build uses a giant Fresnel lens to focus sunlight onto a piece of wood. To get some control out of his build, a 2-axis bed was made from scrounged and junked parts.

The lens in [Johnie]‘s build looks to be about a foot square – more than hot enough to burn a few holes in things from our experience. The bed (hopefully) gets around this problem by being built entirely out of clear acrylic. The idea behind the acrylic bed is that the focused light will pass through harmlessly, and not melt the entire thing.

Now that we think about it, we couldn’t come up with a better project to enter in the Buildlounge laser cutter contest. For everybody else working on their laser cutter projects, the deadline is January 1st. Better get those wrenches out and irons hot, because we’ve seen a few awesome projects for the Buildlounge build off already.

Having experienced quite a bit of trouble getting the Nintendo Wii remotes to work reliably with his home theater projector, [Sprite_TM] designed his own sensor bar replacement. If you’re not familiar, the Wii remotes have an infrared camera in the tip that sense two IR LEDs in the sensor bar that resides above or below your television. The problem is that if you’re too far away, the points of light are not where the remote expects them to be and the cursor will not perform as expected. Since this is a huge projected display it’s no surprise that the player is further away from the screen than the system was designed for.

[Sprite_TM's] solution was to build a projection system for the two IR points. The unit in the picture above is a driver circuit with two IR emitters mounted on a heat sink, each with its own reflector. The reflected beams are shined through a Fresnel lens and projected on the same wall as the TV image. The viewer will not be able to see this light as it’s in a longer wavelength than the visible spectrum. But the Wii remote performs beautifully now and the replacement sensor bar is happily mounted out of sight above the projector.

[PuffMag1cDrag0n] shows us how to make a fairly simple projected LED display. The projector is made from a 13×7 LED matrix and a couple fresnel lenses. The layout and construction is similar to the Lumenlab projector setup, only replacing all the lighting and LCD with an LED array. It communicates via serial port and is powered by a pic micro 16f648. We would love to see an RGB version of this. The directions are a bit rushed, but you should be able to get the gist. Just remember that you need some pretty powerful LEDs to throw a big image.