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56CommentsU Washington, Seattle, WAJoined November 18th, 2005
Created/maintains SCIENCE HOBBYIST, http://amasci.com
  • wjbeaty commented on EGRobotics's instructable Electric Generator Powering LEDs2 years ago
    Electric Generator Powering LEDs

    A pencil is a bit lumpy. It must spin smooth. Find a round pencil, or a plastic pen. But too large an axle has lots of friction, and speed might be too low. The thinner, the better.

    Yes, a piece of coathanger will work. Or a wooden skewer, or even a large nail.

    Diode? Maybe. This generator puts out fairly low voltage. A normal diode eats up nearly 3/4 volt. A 4-diode bridge will wipe out 1.5 volts of your output! Perhaps look for "Schottky" diodes, they use less than half the "Vd" of normal silicon diodes.

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  • wjbeaty commented on Kipkay's instructable Homemade Infrared Goggles! For Under $102 years ago
    Homemade Infrared Goggles! For Under $10

    It's a common misconception that there's a border between "visible" and "IR" wavelengths. There is no such border. See the human visual sensitivity curve http://amasci.com/graphics/IRcurve_HVS.jpg , semi-log graph. Our eyes' longwave filter-function is smooth rolloff from 600nM to 1000nM. Also, if you work with lasers you'll known that humans easily see bright laser light at 800nM, 900nM, 1000 nanometers. Go get your TV remote and look into the LEDs in a dark room: you'll see 800 or 900nM light as dim red flashing.But all this applies to intensely bright single-frequency light, which is a fairly non-natural situation.In more "natural" illumination, the broadband white light of sunlight and electric lights, humans only detect wavelengths out to roug...

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    It's a common misconception that there's a border between "visible" and "IR" wavelengths. There is no such border. See the human visual sensitivity curve http://amasci.com/graphics/IRcurve_HVS.jpg , semi-log graph. Our eyes' longwave filter-function is smooth rolloff from 600nM to 1000nM. Also, if you work with lasers you'll known that humans easily see bright laser light at 800nM, 900nM, 1000 nanometers. Go get your TV remote and look into the LEDs in a dark room: you'll see 800 or 900nM light as dim red flashing.But all this applies to intensely bright single-frequency light, which is a fairly non-natural situation.In more "natural" illumination, the broadband white light of sunlight and electric lights, humans only detect wavelengths out to roughly 700nM, since our eyes' sensitivity to the "visible colors" is overwhelming the long wavelength light out past 700nM. (And, any spots from IR lasers won't be seen unless the room lights are turned off.)These goggles block visible light, so if you're in an environment with lots of IR illumination, you'll see the "infrared world."One layer of Lee congo-blue filter, combined with the HVS (human visual sensitivity) graph, gives this graph: http://amasci.com/graphics/leefltr4.gif Add more layers of congo blue, and the peak moves farther out past 700nM, but becomes smaller.

    Start out with three disks of congo blue, one of red, placed in each side of goggles. (use tissues to wipe off all fingerprints as you stack up the filters. Later you can add more layers of congo blue, which gives a deeper IR view, but needs even brighter sunlight.You can only use them OUTDOORS IN BRIGHT SUMMER SUNLIGHT. These goggles require sunlight, and won't work if worn indoors, or if it's a cloudy day.It helps to go to the original project, http://amasci.com/amateur/irgoggl.html

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