Re: Just Out Of Curiosity


"John Smith" <ghost@xxxxxxxx> wrote in message
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> "Ron Hubbard" <notat@xxxxxxxxxxx> wrote in message
> news:11frcadn0ktc15f@xxxxxxxxxxxxxxxxxxxxx
> >
> > "John Smith" <ghost@xxxxxxxx> wrote in message
> > news:ddiveh$muh$1@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> >>
> >> "Ron Hubbard" <notat@xxxxxxxxxxx> wrote in message
> >> news:11flkn2a5mocm8e@xxxxxxxxxxxxxxxxxxxxx
> >> >
> >> > "John Smith" <ghost@xxxxxxxx> wrote in message
> >> > news:dde0ne$3jp$1@xxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> >>
> >> >> "Ron Hubbard" <notat@xxxxxxxxxxx> wrote in message
> >> >> news:11fjtffi4t26ia7@xxxxxxxxxxxxxxxxxxxxx
> >> >> >
> >> >> > "Ignis Fatuus" <Ignis@xxxxxxxxxxxxxxxx> wrote in message
> >> >> > news:1rhjf19vjsrhhr0q2sedmitgf0gdr4doir@xxxxxxxxxx
> >> >> >> On Wed, 10 Aug 2005 01:52:23 -0700, "Ron Hubbard"
> >> >> >> <notat@xxxxxxxxxxx>
> >> > That's true, I can't break glasses with the scredriver-- well, I could
> >> > if
> >> > I
> >> > grabbed the handle and swung it down... Anyway, this is because the
> >> > screwdriver
> >> > uses modulated sound with a sweep frequency. To be precise, the sonic
> >> > screwdriver
> >> > has an operational frequecy range of 0 Hz to 16 kHz and a sweep
> >> > frequency
> >> > from 10
> >> > to 100 Hz and it can be switch
> >> > programmed to produce a variety of effects. It's one of
> >> > the finest pieces of electronics that I've ever done, and
> >> > I've been in electronics ever since I was 8 years old (that was 31
> >> > years
> >> > ago).
> >>
> >> What is a sweep frequency range?
> >
> > The screwdriver uses frequency modulated sound; I found that works more
> > effectively than just a pure, single frequency. So the circuit employs a
> > VCO
> > (Voltage Controlled Oscillator) that changes frequency with voltage. At a
> > particular voltage you get a particular frequency, but as the voltage
> > rises or
> > lowers the frequency changes accordingly. If you send in a sine wave to
> > the VCO
> > the tone will rise and fall with the sine wave. The frequency of the sine
> > wave
> > can be adjusted to go from no change at all (no sweep), to a very slow
> > rise and
> > fall, to a very fast rise and fall-- the sweep frequency.
> >
> > Sweep frequencies are common in electronics like oscilloscopes, television
> > sets,
> > etc.
>
> Yes. Neat. I was beginning to discover all this late last night; but
> you've provided a very clear and coherent explanation.
>
> So, crystals vibrate when you apply an alternating current (a sine
> wave) - does that mean if I tape two wires to my quartz crystal rock I have
> here and hook it up to a signal generator and apply, ummm, lesssee, I think
> ultra sonic cleaning is done at 40 kHz, so 40 khz signal - does that mean
> I'd get the crystal vibrating at 40 kHz?


Some natural crystals like quartz, tourmaline (sp?), and Rochelle salts a
piezoelectric: that is, they will either produce movement when excited by a
current or they will produce an electric current when you hit them.

Yeah, to a [very] small extent a quartz crystal will vibrate when excited by an AC
current, but with quartz, it takes a considerable amount of electrical power, so
quartz crystals are usually cut into thin slices before they are used in any
ultrasonic application.

Man-made crystals like barium titanate and lead zirconium titanate (as well a
dozen of other different crystal compositions) are a lot better for sonics
applications than quartz. Quartz ids better used to establish frequency stability
in watches and some types of oscillators that require frequency stability.

Ron


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