On Mon, Apr 30, 2012 at 11:46 AM, Robert Rolf <Robert.Rolf@ualberta.ca>wrot=
e:

> >
> >
> >         That is actually the way one can apply an electronic
> > break to an AC motor if one needs to stop one quickly.
> >
> >        There is a man who has invented a quick stop device to
> > stop a table saw blade when it contacts something it shouldn't
> > like your fingers. He says it puts a quick pulse of DC on the
> > motor and then kills the power to it.
> >
> > That method wouldn't work fast enough, even with a massive DC pulse.
> The youtube demo of  'saw stop' shows that it uses a mechanical claw to
> block
> the blade instantly. DC method would allow the blade to rotate enough to =
do
> damage (back EMF only works with MOTION).
>
> http://www.youtube.com/watch?v=3DcTUOhYcw4ZY
> jump to 1:40 to see how it works, and why the claw has to be replaced eve=
ry
> trigger.
> Small price to pay to not lose part of a hand to a blade, but not
> inexpensive.
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Having used a SawStop, I personally _hate_ them.
(based on a TI msp430 too...)

But I've recently heard a radio blurb about a competitive tech - which I
believe Martin was describing. - http://www.whirlwindtool.com/

-Denny
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