On Dec 7, 8:56*am, wrote:
On Fri, 7 Dec 2012 05:29:58 -0800 (PST), "





wrote:
On Dec 6, 5:18 pm, "Michael A. Terrell"
wrote:
" wrote:

On Dec 6, 11:41 am, "Michael A. Terrell"
wrote:
" wrote:

On Dec 5, 2:50 pm, "Michael A. Terrell"
wrote:
" wrote:

You do realize that turning off the saw via the switch is
very different from a power failure, right? Using the
switch there is still power available to the protection
circuitry. During a power failure there is not.

A relay with it's coil across the power line when the switch is on
will stop it, if the power fails. Or configure it with the common
on/off power buttons as a simple motor controller.

It will stop it in 1 ms? Or at least close enough to instantly
to avoid injury, eh? You sure about that? You should go tell
the SawStop guy what a simple, practical new invention you
have. I say, it just doesn't work.

No one claimed that it did, and you just want to whine.

Excuse me, but try to follow the thread. The discussion was
about the SawStop and what happens if power is lost. The
claim was made that it still would work. Then someone claimed
that you could just short the motor and use electromagnetic
braking in case of power loss. The SawStop halts the saw in
1 ms.

Excuse yourself. It doesn't do that when the power fails, and you're
in the dark with a stil spinning blade. It's you that can't comprehend
what is happening in this thread. I introduced the magnetic braking to
stop the blade faster when the motor is turned off. I also told how to
do it in the case of a power failure. It's not my fault that your mother
used to let you play with plastic bags over your head, which caused all
that brain damage.- Hide quoted text -

- Show quoted text -

Let's go back to your first post on this:

Leon:
10+ years ago before the SawStop was in production I questioned Gass
about this. *My TS accident happened after I finished a cut and had
turned the saw off. *The blade was coasting down to a stop when I was
cut. *I wanted to know back then it those bases were covered also.

Michael:
* A modification can be made to table saws with induction or split
phase motors. *You change the power switch from SPST to SPDT, add a
diode & electrolytic capacitor that charges when the motor is
running.
When you switch the motor off, the capacitor discharges through the
motor, causing a rapid braking effect. *This can't be done with
universal motors, since they will run on DC.

In the first sentence of the post you replied to, Leon said "I
questioned Gass about this." * The "this" he was referring to
was the issue if the SawStop still worked in the event of a power
fail. * So, that was the context. *And in posts before that, others
had suggested adding a cap to the SawStop so that it would
work when power was lost.

However, Leon's problem came in the spin-down which wouldn't
necessarily require the SS hardware.

It started with Leon saying this:

"If the saw was running, it will stop if there is a loss of power.
Yes
the stop will work if the saw is turned off. "


The "stop" Leon was talking about was the SawStop.
That was then changed to include normal spin-down,
without a power fail. Whether you had the safety
protection of SawStop in those events. leon was
checking to see what SS does in those cases.
SawStop halts the
saw in 1ms, apparently the timeframe you need to avoid
injury if you're about to hit the blade with your finger.

So, first, absent some extraordinary electromagnetic
braking design, I say you're not going to halt the saw
in the 1ms timeframe, that is fast enough to prevent
an injury if you shove your finger into the spinnng blade.




*Leon wanted to know if they'd
covered this case.

Yes, the case he was talking about was if SawStop would
work in power loss or normal spin-down,




*Michael was noting that this problem could have
been corrected, cheaply, without the expensive SS hardware and without
blowing a SS cartridge and blade when it occurred.

You're mixing two things here. Again, the case Leon
brought up was if SawStop works under power loss or
spin-down. That can halt the blade even if you're finger
is shoved into the blade, without causing injury.

Michael's proposed solution, is incapable of that.
Do you agree? It's a nice feature that, if it could be
implemented cost effectively, would bring the spinning
saw to a quicker stop. But I say again, absent some
extraordinary system, it's not going to halt that spinning
blade in 1ms.

And if it could, then you would not need the SawStop
at all because you could just use electromagnetic
braking all the time to stop it. It would be better because,
as you say, there is no blown cartridge.






So, you replied about using electromagnetic braking. * Sorry,
but in that context, it sure appeared that you were talking about
adding that in addition to the SawStop, so that it would stop
it in a similar fashion if the power failed. * Or at the very least,
that you were suggesting electromagnetic approach as a safety
device for protection to replace the SawStop.

Replace? *I didn't get that. *In addition, sure.

But it was offered "in addition" in the context of SawStop
working during power fail or normal spin-down, implying that
it could offer the same coverage. It could not. Since then,
I think we've learned that SawStop works during normal
saw shut-off (not 100% sure about that) and might work
for a sec or so in the event of power loss.

So, I think we have arrived at the point where if you wanted
to improve the protection SS offers you could easily add some
small power storage to keep it active during spin-down
in a power failure. And you have a possible alternate
feature you could add to a saw that would significantly
reduce the spin-down time using electromagnetic braking
that would work every time the saw is shut off or loses
power. But I don;t see the latter being of much use in saws with
SawStop. Once you have that, you might as well just
rely on it.




So, instead of hurling insults, perhaps you should learn
to write less ambiguously.

It was perfectly clear to me. *I understand the issues involved,
though.- Hide quoted text -

- Show quoted text -

See, the above remark is how you so frequently wind up in
nasty spats with so many folks here. Was that necessary?
I have not been anything other than civil to you in this thread.