Re: 3 Phase brushless motors

Hi Robert, from your motor description and chip
description these sound very much like the flat
"pancake" 3 phase motors used in VCRs as capstan
motors.

The entire system is not really suited to use
in a CNC machine because the system is designed
for ONE thing, to keep a VERY constant speed
(phase locked) with minimum speed ripple.
Hence the triple phase design with hall phase
angle sensors. It is designed to transport the
tape in the VCR with a very regulated speed.
I don't think they have very many steps per rev,
possibly 24 steps/rev if they are the ones I know.
And they expect a fairly constant load.

If you must use them for CNC it might be easier
to just wire up 3 transistors as a simple
unipolar (open loop) driver. This should work
but they really don't have that much torque
compared to a 5v 1A 23-frame stepper motor,
which you can get almost anywhere for a few
bucks. :o)
-Roman

--- In CAD_CAM_EDM_DRO@y..., "Robert" <cncrouterusa@n...> wrote:
> Hello List,
> This is for some of the electronics minded folks. I have some small
3Phase
> brushless motors and drivers I would like to use on a homebuilt
engraver.
> They have Hall effects embedded in the motors for feed back to the
driver
> chip , a TA7712. I have a PDF of the chip that shows how to monitor
and set
> the speed using passive components but think this is useless without
proper
> software. I was thinking that by using Turbo CNC I might be able to
use them
> by sending the signals directly into the power circuit. At this
point all I
> have is START, DIRECTION, and BRAKE signals to work with. These
motors are
> very powerful and high rev rates, so with proper reduction could
work well.
> Any thoughts would be appreciated. I have 2 sets of 3 for hacking
up.
> Robert