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  1. poor mystic

    Signal generator to drive Ultrasonic transducer

    :) The industrial guys use horns - see Wikipedia: "Ultrasonic horn" is the search term you need.
  2. poor mystic

    Comedy Thread

    OK so after a few days I cheated... A highly ranked spoiler.
  3. poor mystic

    Comedy Thread

  4. poor mystic

    Comedy Thread

    MRI operators use a test lab to calibrate their machines.
  5. poor mystic

    Comedy Thread

    :) Hmmm... I can only suppose a dog might be more likely to hurry if he were chaste?
  6. poor mystic

    Signal generator to drive Ultrasonic transducer

    :) I've been thinking about piezo transducers for a while, and I can offer an insight. In circuit, an unloaded transducer is like a capacitor with a resistor in series - a CR circuit with quite a small value of R. When the transducer is fitted in a machine and experiences a mechanical load, the...
  7. poor mystic

    Today's dose of comedy!!

    :)
  8. poor mystic

    Measuring an NST Output

    Hi :) Quite frankly I'm afraid to advise you, because your plan is not safe. It is not safe to make your first experiments with electricity on a Neon Sign Transformer. I'm worried that the device under test produces high current at high voltages - way enough to kill in less than a second, no...
  9. poor mystic

    Sony SLV-N750 fast rewind help

    Hi :) It might be possible to get a new tape transport mechanism. Try a spare parts supplier. Mark
  10. poor mystic

    Signal generator to drive Ultrasonic transducer

    Hi :) I'm not sure why you need a sin signal. This is a capacitive device which you can pour charge into, and pour it back out. It seems to me that it would be easier to drive this device with a square wave. Why not use a totem pole and just drive it plus and minus as hard as you can?
  11. poor mystic

    High current, 40 A to 100 A, current limiting devices other than a resistor

    yeh ... nice of you to put it that way danadak:) I saw I'd offered a no-go idea... but couldn't find the delete button mm well. Tungsten is of course PTC, and NTC is wanted, as mentioned earlier in the thread.
  12. poor mystic

    High current, 40 A to 100 A, current limiting devices other than a resistor

    Some arrangement of tungsten filament light bulbs might do the trick. One of these 200W 24V tungsten lamps in series with each Peltier module would be pretty safe. https://www.amazon.com/OSRAM-200W-MR16-Tungsten-Halogen/dp/B002DQVTIQ:)
  13. poor mystic

    Whistle responder circuit

    I like the LM567 Tone Decoder idea, but I doubt that a simple thing like that will really be very reliable. (Of course if you're in a special managed environment like a stage and you can turn on a switch when you want to demonstrate the gadget it'll seem to work fine.) You might be having fun...
  14. poor mystic

    match a cellphone with a waveguide

    ... to filter and amplify my question - I'm a bit confused by the tininess of the antenna on the cellphone circuit board. Through some amazing geometry, there is a match between the tiny antenna and a signal whose wavelength is perhaps 20 times the aerial length. So, can a signal be led down a...
  15. poor mystic

    match a cellphone with a waveguide

    Hi guys :) I want to use a cellphone to test a novel antenna (which I don't want to describe). The antenna will improve the signal from a cellphone tower and feed a waveguide. Does anyone here have experience or knowledge to help me in matching the tiny antenna in the phone with such a signal...
  16. poor mystic

    12v DC Doorbell Chime

    :)
  17. poor mystic

    12v DC Doorbell Chime

    Hi :) I once used a pair of dynamo telephones to do a similar job and more. Twirling the dynamo generated an AC voltage which not only rang the distant bell, but also powered a few minutes speech, so that no batteries were needed. I just put a simple 4 diode full-wave rectifier and a 100V...
  18. poor mystic

    A new approach to seismometry?

    Hi guys (especially Dave) ... not even sure this is really "off-topic" https://www.wired.com/story/how-underground-fiber-optics-spy-on-humans-moving-above/ :)
  19. poor mystic

    source of replacement potentiometer

    Did you try the WD-40 trick? Should be good for a month or 2
  20. poor mystic

    Analog frequency meter

    Ohh those are for getting a generator to run at the right speed. They're a bit like a mechanical tuning fork.
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