Recent content by maimonides

  1. M

    Ultrasonic Standing Wave Suspension could the transducer support itself?

    I fear you overlooked something. They state clearly : "The first system was able to lift a weight of 3 kg using an electrical input power of only 16 W. Based on the surface area, a lift capacity of 11.5 kN/m2 was reached." 11500/30 ~ 380; 16W* 380 ~ 6000W, so even assuming peripheral losses...
  2. M

    Determining Compass Bearing from Resultant Angle

    Maybe a nitpick, but: Are you sure you want/need to add wind speed and (water) current? (I assume water because of "current" and the values you use)
  3. M

    Schools Oil mechanics universities

    Not Germany, but have a look at http://en.wikipedia.org/wiki/University_of_Leoben
  4. M

    Surface area of a bulb filament

    There are special lamps for precision measurements in photometric, for example this one: http://www.pyrometer.com/ribbon_lamp.html I´ve found one source for emissivity of tungsten here: http://www.monarchserver.com/TableofEmissivity.pdf [Broken] If you expect high accuracy in...
  5. M

    Gravitational Vortex Power plant

    I replied to a similar question here https://www.physicsforums.com/showthread.php?t=520878 about two years ago. Maybe i was a bit unfriendly, but things haven´t changed much since then. Most of the technical information I linked to is in German, so you´ll have to translate.
  6. M

    Is it possible to power a freight train with an animal motor?

    As jtbell points out, some of the first railroads started with animal traction, at least in Europe. http://en.wikipedia.org/wiki/Saint-Étienne_to_Andrézieux_Railway http://de.wikipedia.org/wiki/Pferdeeisenbahn_Budweis–Linz–Gmunden (sorry, no English version available). Steam locomotives soon...
  7. M

    Conversion of Voltage into Radiation counts

    You might try evaluating the output of a proportional counter using a very sophisticated digital storage oscilloscope, but that would be a lot of effort and probably not worth it. http://en.wikipedia.org/wiki/Proportional_counter
  8. M

    Vacuum possible from Gaede mercury pump from 1913.

    I used a mercury diffusion pump (quite) some time ago. With a bit of heating the vacuum got down below 10-5 torr. Of course there was a cryotrap between the pump and the vacuum vessel (liquid nitrogen).
  9. M

    Power on/off bi-color led circuit?

    If this is about safety (outside of a purely experimental setting) you better check the codes and regulations applicable. Probably there are a lot of them. You will find that there are standard circuits designed to comply with the codes. Just find out and use them. Don´t try to cut costs or to...
  10. M

    Collimating incoherent light emitted by a LED

    You´re perfectly right about the pinhole. The standard way of producing a parallel beam used to be: Use a lens to produce a (reduced) image of your light source onto/into a pinhole. Try to capture as much of the light as possible. On the other side of the pinhole, use a lens to produce your...
  11. M

    Output buffer for audio

    In theory you are correct with a 20db conversion factor. But it applies only for a point source, far field conditions and negligible influence of the measuring microphone, and you cannot assume all of that. You can only use the 20db as a sanity check. Yungman is essentially right: you are...
  12. M

    Output buffer for audio

    A headphone/earphone driver needs to produce sound pressure in the ear only, so it is tested on an ear simulator (a small, short tube, you can find the details in the datasheets in the links you gave). A "normal speaker" is expected to produce sound everywhere around it. Apparently this needs...
  13. M

    Output buffer for audio

    The speakers you linked to are for headphone/earphone use, forget about them. (The db numbers don´t mean the same as in normal speakers). You need size for a decent midrange, don´t go below 30mm diameter if you can. (A cordless phone phone I repaired a few weeks ago has a 36mm speaker for...
  14. M

    Magnet on fridge

    Quite a few deep freezers heat the sealing surfaces to prevent buildup of ice. But I´ve never heard of one using electromagnets. As vk6kro said, the magnet in the door seal is strong enough. I disassembled seal once and found a strip of magnetic material all along the seal.
  15. M

    Cheap Hydrostatic Testing Chamber

    You might be interested in this.
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