I think I found a new toy for you.
http://www.woodwerks.com/mirka-ceros...er-p-9105.html

Pretty impressive.

R

On Feb 1, 6:31*pm, RicodJour wrote:
I think I found a new toy for you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

R

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Robatoy wrote:
On Feb 1, 6:31 pm, RicodJour wrote:
I think I found a new toy for
you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

R

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Robatoy,
Do you mean that there are brushless pulsed DC motors?
Thanks,
Kerry

On Feb 1, 7:04*pm, "Kerry Montgomery" wrote:
Robatoy wrote:
On Feb 1, 6:31 pm, RicodJour wrote:
I think I found a new toy for
you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

R

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Robatoy,
Do you mean that there are brushless pulsed DC motors?
Thanks,
Kerry

Yes, I think so..isn't that the type that spins hard drives?

In article ,
Robatoy wrote:
...snipped...
There is no such thing as a brushless DC motor. Pulsed DC , sure...

Perhaps I misunderstand but couldn't that same logic be used to state
that there is no such thing a s brush DC motor? After all the brushes
and commutators are just another way of "pulsing" the DC at the
correct timing.


--
There are no stupid questions, but there are lots of stupid answers.

Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org

On Feb 1, 8:03*pm, (Larry W) wrote:
In article ,Robatoy wrote:

...snipped...

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Perhaps I misunderstand but couldn't that same logic be used to state
that there is no such thing a s brush DC motor? After all the brushes
and commutators are just another way of "pulsing" the DC at the
correct timing.

--
* *There are no stupid questions, but there are lots of stupid answers.

* * *Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar. org

Many brushed motors will run on either AC or DC.

On Feb 1, 6:58*pm, Robatoy wrote:
On Feb 1, 6:31*pm, RicodJour wrote:

I think I found a new toy for you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.


There is no such thing as a brushless DC motor. Pulsed DC , sure...

Alright...does that mean you have/have used the unit, or just
generally disapprove of it based on marketing claims? The video
highlighted some nice features.

I am not a motor guy, as recent threads may have indicated, so I have
to ask why Wiki has the first section on the differences between
brushed and brushless DC motors.
http://en.wikipedia.org/wiki/Brushle...electric_motor
Is this one of those semantics things, or is the article wrong? It
looks like a reasonable Wiki article and there are none of the usual
caveats at the top of the page seen on sketchy info articles.

R

On Feb 2, 12:07*am, RicodJour wrote:
On Feb 1, 6:58*pm, Robatoy wrote:

On Feb 1, 6:31*pm, RicodJour wrote:

I think I found a new toy for you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Alright...does that mean you have/have used the unit, or just
generally disapprove of it based on marketing claims? *The video
highlighted some nice features.

I am not a motor guy, as recent threads may have indicated, so I have
to ask why Wiki has the first section on the differences between
brushed and brushless DC motors.http://en.wikipedia.org/wiki/Brushle...electric_motor
Is this one of those semantics things, or is the article wrong? *It
looks like a reasonable Wiki article and there are none of the usual
caveats at the top of the page seen on sketchy info articles.

R

There's an upside to a sander having some weight, unless you're
holding it upside down or on a vertical surface for long periods of
time. I'm certainly intrigued by the concept, mostly because they have
made it quiet. The weight reduction was already available by using air
driven sanders, but they're noisy..and probably a bit heavier too....
and if you include the compressor, a lot more money than the Mirka
Ceros.

I have not used one, but from experience, Mirka is one of those
companies that take their products very seriously so now I will have
to try one. I will be in touch with a Mirka rep soon.

Price is not all that bad, considering.

Now the 'brushless' part. It probably is a marketing attempt at
projecting a zero maintenance image, and that's fine. The DC part bugs
me, because to me, DC is a continuous flow of energy, creating an
image of linear power application, i.e. smoothness. From a technical
standpoint, and I admit to picking nits, it is inaccurate although
most people probably couldn't give a rat's ass about that.
The range of RPM they claim, would indicate to me that the pulsing of
the DC would be at a high enough frequency that the application of
power would be pretty smooth.

The agility, the fit in the hand, all are factors that will determine
whether or not I will like it, for there is still a cord, and a
frickin' hose that I find the most annoying things of handling any
sander.

And, as I have touched on earlier, lightness isn't always a plus. To
have some mass between your hand and the buzzing disk functions as a
barrier. (I am glad my 12ga shotgun weighs as much as it does for the
same reason.)

Thanks for bringing the product to my attention.

Robatoy wrote:
On Feb 2, 12:07 am, RicodJour wrote:
On Feb 1, 6:58 pm, Robatoy wrote:

On Feb 1, 6:31 pm, RicodJour wrote:

I think I found a new toy for
you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Alright...does that mean you have/have used the unit, or just
generally disapprove of it based on marketing claims? The video
highlighted some nice features.

I am not a motor guy, as recent threads may have indicated, so I have
to ask why Wiki has the first section on the differences between
brushed and brushless DC
motors.http://en.wikipedia.org/wiki/Brushle...electric_motor Is
this one of those semantics things, or is the article wrong? It
looks like a reasonable Wiki article and there are none of the usual
caveats at the top of the page seen on sketchy info articles.

R

There's an upside to a sander having some weight, unless you're
holding it upside down or on a vertical surface for long periods of
time. I'm certainly intrigued by the concept, mostly because they have
made it quiet. The weight reduction was already available by using air
driven sanders, but they're noisy..and probably a bit heavier too....
and if you include the compressor, a lot more money than the Mirka
Ceros.

I have not used one, but from experience, Mirka is one of those
companies that take their products very seriously so now I will have
to try one. I will be in touch with a Mirka rep soon.

Price is not all that bad, considering.

Now the 'brushless' part. It probably is a marketing attempt at
projecting a zero maintenance image, and that's fine. The DC part bugs
me, because to me, DC is a continuous flow of energy, creating an
image of linear power application, i.e. smoothness. From a technical
standpoint, and I admit to picking nits, it is inaccurate although
most people probably couldn't give a rat's ass about that.
The range of RPM they claim, would indicate to me that the pulsing of
the DC would be at a high enough frequency that the application of
power would be pretty smooth.

The agility, the fit in the hand, all are factors that will determine
whether or not I will like it, for there is still a cord, and a
frickin' hose that I find the most annoying things of handling any
sander.

And, as I have touched on earlier, lightness isn't always a plus. To
have some mass between your hand and the buzzing disk functions as a
barrier. (I am glad my 12ga shotgun weighs as much as it does for the
same reason.)

Thanks for bringing the product to my attention.

Robatoy,
Your comment about the shotgun reminded me of my nephew letting his 14 year
old son fire their 12ga for the first time. The boy was asking if they could
saw off the barrel, and maybe cut the stock down too, so it would be like
he'd seen in the movies. After firing it for the first time, held tightly
against his shoulder, and almost being knocked down, the son decided that
the mass didn't need to be reduced at all!
Kerry

On Feb 2, 12:07*am, RicodJour wrote:
On Feb 1, 6:58*pm, Robatoy wrote:

On Feb 1, 6:31*pm, RicodJour wrote:

I think I found a new toy for you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Alright...does that mean you have/have used the unit, or just
generally disapprove of it based on marketing claims? *The video
highlighted some nice features.

I am not a motor guy, as recent threads may have indicated, so I have
to ask why Wiki has the first section on the differences between
brushed and brushless DC motors.http://en.wikipedia.org/wiki/Brushle...electric_motor
Is this one of those semantics things, or is the article wrong? *It
looks like a reasonable Wiki article and there are none of the usual
caveats at the top of the page seen on sketchy info articles.

R

BTW, there is a discussion on on at FOG (Non-Festool Power Tools
section, and it seems positive.)

On 2/1/2011 10:05 PM, Robatoy wrote:
Now the 'brushless' part. It probably is a marketing attempt at
projecting a zero maintenance image, and that's fine. The DC part bugs
me, because to me, DC is a continuous flow of energy, creating an
image of linear power application, i.e. smoothness. From a technical
standpoint, and I admit to picking nits, it is inaccurate although
most people probably couldn't give a rat's ass about that.
The range of RPM they claim, would indicate to me that the pulsing of
the DC would be at a high enough frequency that the application of
power would be pretty smooth.

Most electric motors have some way to drive magnets to create a rotating
magnetic field. (There are also electrostatic motors which we will ignore
for the purposes of this discussion.)

A 'brushed' DC motor uses brushes and a commutator to vary which windings
are energized to create the rotating magnetic field. The windings are
usually on the rotor and the rotor's magnetic field rotates backwards
relative to the rotor. The power flow to a brushed DC motor is only 'somewhat'
smooth or continuous. The actual current flow into the motor goes up and
down as the commutator applies voltages to the different windings. (You
cannot instantaneously change the current in a winding from zero to maximum
and then back to zero.) Compare the noise from a 'universal' motor such
as the ones on inexpensive table top saw versus the quietness of an
induction motor such as the ones found in most better table saws. The
universal motors are both electrically and acoustically noisy.

A 'brushless' DC motor uses electronics to drive the windings. Just like
the brushed DC motor, the winding drive currents are changed as the motor
turns. The winding drive signals may be simple on/off voltages (like you
would get from a brushed DC motor's commutator) or some something more
complex. I worked on pen plotters which used brushless DC motors for
positioning. Each motor had two drive windings. The windings were driven
with variable frequency sine and cosine signals (i.e. sine waves with a 90
degree phase difference) which produced constant torque and power out of
the motor. So they were very smooth and they could be run at a wide range
of speeds down to a small faction of an RPM. They were very quiet, compact,
and extremely efficient.

Note: The driven windings in a brushless DC motor are usually on the stator
(the non rotating part of the motor) instead of the rotor. This is done
simply to eliminate the need for any electrical connection to the rotor.


Dan

"Robatoy" wrote:

Many brushed motors will run on either AC or DC.
----------------------
They are known as universal motors.

Very common for hand held electrical devices found in shop and/or
kitchen.

Lew

I think you would find the field does **NOT** rotate but rather attempts to
stay in the same place relative to the field coils.

Think about that one...LOL


"Dan Coby" wrote in message
...
A 'brushed' DC motor uses brushes and a commutator to vary which windings
are energized to create the rotating magnetic field.Dan

On 2/2/2011 7:12 AM, Josepi wrote:
I think you would find the field does **NOT** rotate but rather attempts to
stay in the same place relative to the field coils.

Think about that one...LOL


"Dan wrote in message
...
A 'brushed' DC motor uses brushes and a commutator to vary which windings
are energized to create the rotating magnetic field.Dan

I am not going to bother to try to straighten out your annoying top posting!


However as I said in the very next sentence of my posting (which you snipped):

"The windings are usually on the rotor and the rotor's magnetic field rotates
backwards relative to the rotor."

Yes. In the typical brushed DC motor, the backwards rotation of the rotor's
magnetic field results in a field which is stationary relative to the stator
field.

My point is that the magnetic field of either the rotor or the stator or both
has to change (relative to what is causing the field) to cause the motor to
move. In a brushed DC motor it is usually the rotor's field. In a brushless
DC motor it is typically the stator's field. In an induction motor is is
typically both.


Dan

I will straighten out your bottom posting as I am not that lazy.

I understood what you meant but the iincorrect information was there. You
may have learned something. The back-paddle was not necessary.

All the best.



"Dan Coby" wrote in message
m...
I am not going to bother to try to straighten out your annoying top posting!

However as I said in the very next sentence of my posting (which you
snipped):

"The windings are usually on the rotor and the rotor's magnetic field
rotates
backwards relative to the rotor."

Yes. In the typical brushed DC motor, the backwards rotation of the rotor's
magnetic field results in a field which is stationary relative to the stator
field.

My point is that the magnetic field of either the rotor or the stator or
both
has to change (relative to what is causing the field) to cause the motor to
move. In a brushed DC motor it is usually the rotor's field. In a
brushless
DC motor it is typically the stator's field. In an induction motor is is
typically both.


Dan


On 2/2/2011 7:12 AM, Josepi wrote:
I think you would find the field does **NOT** rotate but rather attempts to
stay in the same place relative to the field coils.

Think about that one...LOL

"RicodJour" wrote in message
...
I think I found a new toy for you.
http://www.woodwerks.com/mirka-ceros...er-p-9105.html

Pretty impressive.

Searching for something else, I came across this which appears to be a
similar product.

http://www.harborfreight.com/6-inch-...der-98895.html

"Robatoy" wrote in message
...
On Feb 1, 6:31 pm, RicodJour wrote:
I think I found a new toy for
you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

R

There is no such thing as a brushless DC motor. Pulsed DC , sure...


Yes there is. The center of the motor, usually called the armature is
instead, stationary, and has three phase windings on it. The outside of the
motor has rare earth magnets, and spins, doing the work.

The controller rotates the 3 phase windings electronically to make the case
turn.
--
Jim in NC

On Feb 5, 12:07*pm, "Morgans" wrote:
"Robatoy" wrote in message

...

On Feb 1, 6:31 pm, RicodJour wrote:
I think I found a new toy for
you.http://www.woodwerks.com/mirka-ceros...tric-random-or...

Pretty impressive.

R

There is no such thing as a brushless DC motor. Pulsed DC , sure...

Yes there is. *

No there isn't.

The center of the motor, usually called the armature is
instead, stationary, and has three phase windings on it. *The outside of the
motor has rare earth magnets, and spins, doing the work.

The controller rotates the 3 phase windings electronically to make the case
turn.
--
Jim in NC

There is no 'phase' to pure DC. The controller pulses the DC to create
'phase' as you put it. Put a scope on the power going to the 'DC-
brushless motor and see for yourself. It has a wave-form although not
a reversal in polarity such as AC per cycle.