Re: [ATM] Voice coil actuators was: DC Motor for grinding machine question

["Don Clement" <don_clement@charter.net>]

Mike answered the question exactly. I was going to use the voice coils to
dither the tool pseudo random signal. Mike may be right about that there is
no effect of periodic vibrations introduced by the bearings or driving
motor/components. It might be fun just to find out for sure. Test that
theory!



Don





> Hi,
>
> Many are asking questions about this.  I don't think Don is intending
> to drive the strokes of the tool with voice coils.  I believe what he
> intends to do is shake the tool a little bit with the coil actuator
> (or motor) in a pseudo-random way (using pseudo-random noise.  This
> "noise" will swamp out any periodic vibrations introduced by the
> bearings or driving motor/components.  Since is is nearly random, it
> won't introduce any periodic vibrations itself.
>
> It's a neat idea.
>
> Don believes these periodic vibrations might have an effect on the
> surface roughness of the mirror.  Personally, I don't, but I've been
> wrong before!
>
> Mark Holm wrote:
> > As I recall, most high end audio amps spec down to about 20Hz.  Below
> > that, humans just hear the windows rattling.  The low C on a 32 foot
> > organ stop has a fundamental frequency of about 16 Hz.  I hear that as
> > more of a vibration than a tone.  (But what a vibration!)
>
> Now a little off-topic for the audiophiles among us....
>
> Audio amps can be AC-coupled (capacitor in series in the output,
> blocking DC), as tube amps often are, or DC-coupled (no capacitor in
> the output).  Those that are AC-coupled will roll off in the low
> frequencies until the response is zero at DC.
>
> Good audio amps try to get down into the infrasonic range (below 20
> Hz) because that vibration is important in two ways - 1) It's fun to
> shake the walls, and 2) accurate reproduction of the low-frequency
> information is important in conveying the ambiance and acoustic
> properties of the recording venue.
>
> Mike Lockwood
>
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>

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