Author: Eliot

1332 Articles

IR Triggered Projection Clock

June 26, 2006 by 7 Comments

projection clock

Inspired by raphnet’s projection clock, imakeprojects decided to build their own version. The clock only turns on when a source of IR light is pointed directly at it (i.e. television remote). This would be good for a room that you would normally like as dark as possible, like a home theater. The clock uses a 38kHz IR detector to trigger a Luxeon LED. You need to rotate the polarizing filter on the clock so that an inverse image will show up on the wall. imakeprojects was able to get a clear image without a lens while projecting up to 6 feet.

[thanks trebuchet03]

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Alpha Radiation Visualizer

June 25, 2006 by 47 Comments

alpha visualizer

[Jared Bouck] certainly has a unique project on his hands this time. He started out wanting to build a somewhat complex system for visualizing Cherenkov radiation. With a little investigation he found some new ideas and decided to build a really compact apparatus. Cherenkov radiation is seen as a blue flash when a particle passes through a medium at a speed greater than the speed of light in the medium. Jared used a webcam CCD as the medium and a small piece of radioactive americium sourced from a smoke detector. The camera housing is sealed from any light leaks and is shielded to block EMI. Watching the camera output you can see flashes of white and blue streaks.  It’s a neat home built demo and I bet it could be used as a random number generator as well. In the real world, scientists use Cherenkov radiation detection to determine fission reaction intensity, measure radioactivity in spent fuel rods, and detect the origin of cosmic rays. Similar techniques are used in neutrino detectors like the massive IceCube project.

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Updated Lightweight Eye Tracker

June 24, 2006 by 16 Comments

eye tracker

[Igor Carron] pointed out that Derrick Parkhurst and his colleagues at Iowa State have been hard at work improving their lightweight eye tracker that we covered in January. The new version uses digital cameras instead of analog ones. This time they’ve included step by step build instructions instead of just a PDF describing the device. Most of the build involves removing the CCD from a couple cheap webcams and then building an extension back to the board. All of this work is part of the Human and Computer Vision Laboratory’s open-source openEyes project. If you want a quick intro into how this type of eye tracking works I suggest reading our previous post.

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Unlimited Cellphone Calling For Cheap

June 23, 2006 by 46 Comments

nextel

Every couple months I get a tip about how to get unlimited calling for minimal money. They usually involve some less than elegant forwarding, but I figured I’d post one and hopefully be done with this topic. Here is [van12]’s version posted on Howard forums. First you need a cellphone plan that has free inbound/outbound calling to your home number. You use a home number from a VOIP provider that lets you forward inbound calls to your cellphone. By calling home you can use the VOIP providers cheap unlimited plan to make calls.

[UPDATE: HoFo seems to be blocking us with a registration page now]

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Computer Controlled Light Cube

June 22, 2006 by 13 Comments

led light cube

[Alex Hornstein] was bored one Saturday and decided to do something with the large pieces of scrap acrylic he had found. He built a cube and attached 15 RGB LED clusters along with 4 GB LED sticks. It takes 50W of power. The controller is built from ATmega48 and is controlled via serial commands over a wireless link from Spark Fun. You can find schematics, pictures, and video on his site, Art is Wrong.

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Sound Based Airsoft Chronograph

June 21, 2006 by 32 Comments

airsoft chronograph

Seattle Airsoft has a great post on measuring BB velocity using a microphone. They use two pieces of paper separated by 10 feet with a microphone by each one. Audacity is their program of choice for recording. If you look at the waveform after firing you’ll see three distinct spikes: one from the firing mechanism and one from each paper strike. They compared the results from this method to those of an actual optical chronograph. The mic seemed to deviate far less.

[thanks aqua_scummm]

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VGA CAT5 Extension Cable

June 20, 2006 by 30 Comments

rj45 cable

[Ladada2001] sent along a project link for building a VGA extension cable using CAT5. This particular project was for a projector with BNC connectors. This has been a particularly popular (and easy) topic in the past. We’ve seen an example from ElephantStaircase. The 5-in-1 cable featured in Make also had provisions for VGA. If you build one of these cables you should be able to get decent performance at 50 feet.

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