About logical

Jan. 10, 2009
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  • logical commented on How-ToDo's instructable Simple Tesla Coil4 days ago
    Simple Tesla Coil

    Circuit wise, this isn't really that complicated but I'd hardly call it a Tesla coil either. What you have here is basically a step up transformer and no more and with a ratio of 1:100 (10 primary / 100 secondary) and a 25V input, you'd get around 25,000 out but that alone doesn't make it a Tesla Coil, it simply makes a transformer. A genuine Tesla Coil while still relatively simply to make, does a little by achieving a higher than expect output for a given turns ratio.A genuine Tesla Coil takes a simple tuned, resonant circuit driven by an already high voltage such as a neon sign transformer or (or even better, a Pole Pig) to drive a 'tuned' primary via an LC (tank) circuit. This is a little more than just pumping AC into the primary. Both the primary/secondary and the tank circuit are all carefully tuned to hit resonance at which point, this no longer behaves like a classic transformer and suddenly this is generating much higher voltages than you'd expect for the chosen turns ratio. This circuit may well be self-oscillating but without a capacitor in sight, we no longer have the all important LC (tank circuit) so it's not a Tesla Coil.That btw, is probably a good thing as a good Tesla Coil can be rather dangerous if you don't know how to operate it safely ;-)

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  • logical commented on bkb37's instructable Portable Holographic Displayer (Holo-Watch)8 months ago
    Portable Holographic Displayer (Holo-Watch)

    Very cool but a 'Hologram' ? When are people going to stop calling these holograms and find an original or more specifically an accurate description? These things are a 4 way variation on a centuries old theatrical illusion called 'Peppers Ghost'. It's not even 3D. Until yesterday, I couldn't even convince my son these weren't holograms. Why? Because yesterday, my son got to spend a few hours with one of the remaining 'Holographers' in the UK, Inaki Beguiristain. At this workshop, we got to see some of Inaki's works, some of the best Holograms ever made in addition to learning what they are, the science and how they are made and a chance to make his own. "That's just wrong! I'm looking into a box but it's just a single, thin bit of glass? That's not normal!" As he looks at another example of some jewelry behind a magnifying glass, "It looks like its magnifying the dial and the winder? ... hang on ... OMG, the magnifying glass really works, I'm not joking, That's impossible!, it's just a bit of glass?" Just a few of the reactions as he looked through Inaki's holograms. This from a kid who thinks photo's, art and paintings are boring but this was to be a rare occasion when the computer mad gamer is more interested in visiting galleries than a trip to a computer museum filled with retro consoles, Oculus Rift and all the usual stuff that keeps our kids glued to a 27" monitor. Unfortunately, he'll have to make do with this very brief intro as I can't afford the £700, full day, 1 to 1 introductory coarse in Holography."Three-dimensional image formed by the interference of light beams from a laser or other coherent light source. Photograph of an interference pattern which, when suitably illuminated, produces a three-dimensional image" Oxford Dictionary :)

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