Re: [CAD_CAM_EDM_DRO] Re: Gecko G420's question

Thank you Eric, for your informative response. I expect when the drives
actually come out there will be more information available on its
"commutation scheme." I have some brushless servo motors but they have
pancake synchro resolvers mounted on them. Motors are made by Getty's, and
I ran into a dead end trying to get info from the new owners of that
company.

Thanks again, Eric.

Tom Eldredge

----- Original Message -----
From: "Unterhausen Umberto" <unterhausen@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, April 29, 2002 9:29 PM
Subject: [CAD_CAM_EDM_DRO] Re: Gecko G420's question


> David Eldredge writes:
>
> "Gentlemen," -- loosely speaking in my case
>
> "Does anyone know what type of feedback the G420's are
> expected to use?
> Hall effect or encoder?"
>
> As I recall, they are Hall with encoder. In my
> collection of drives and motors there are: Halls,
> Halls with encoders, Halls with encoders with some
> kinda absolute track, encoders with simulated halls,
> and resolvers.
>
> When you use Halls with encoders, there are two
> approaches. The first is to commutate the motor as if
> you just had the hall signal and use the encoder to
> keep track of your error. In this sense, the drive
> doesn't know if the Hall is about to signal to go to
> the next phase or not, it just does the commutation
> with the feedback. My guess is that this is how the
> Geckos will be. Other drives require that they know
> the encoder counts and then use sinusoidal
> commutation. I like to think of a brushless motor as
> a stepper motor with a very small number of steps per
> rev, even though Mariss says it's not true. You can
> get them to step, but you will hate yourself in the
> morning. The way I look at it a stepper motor
> requires commutation, a dc motor does it thru
> mechanical means.
>
> "Will the G420s save money on servo motor cost? I
> understand the
> benefits of eliminating brushes and commutators, but
> are there many sources
> of motors for them? "
>
> Brushless took over the machine tool and robotics
> market sometime in the mid-1990's and thus they are
> the wave of the future. Ebay has a regular supply of
> brushless motors. I would say that high quality
> brushless motors are more numerous on ebay than high
> quality dc motors, but I don't really look that hard
> for the DC motors. New brushless motors cost at least
> $500, but all the other options are also
> breathtakingly expensive if you buy them new retail.
>
> I skip the question about making them.
>
>
> "How about some more discussion on what this new
> development will bring
> to the hobbiest CNC guy."
>
> The Gecko drives make brushless motors available to a
> person that just wants to go out and buy a drive. The
> competition costs $500 - $1000. The motors rarely go
> for more than $100 on ebay, and almost never go for
> more than $200. Obviously, it's still high end, and
> it is considerably more involved subject than DC
> motors or steppers.
>
>
> Eric
>
>
>
>
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