But you said the fourth is a common - aka you have a star winding, the
fourth one is the middle. Just leave it unconnected.

Tamas


On Thu, Apr 10, 2008 at 7:18 PM, Nicola Perotto <nicola@nicolaperotto.it>
wrote:

> Hi,
> before posting here I read all app notes and searched in internet a lot.
> All that i found speaks about 3 wire motors. But harddisk motor has 4
> wires! So i have some doubts on these!
> The motor has no sensors. (I opened one...)
>       Nicola
>
>
> Tamas Rudnai wrote:
> > Hi Nicola,
> >
> > That is a BLDC motor (Brush Less DC motor). There are couple of app
> notes on
> > driving such a motor at Microchip web site if you look at the motor
> control
> > notes.
> >
> > What you should know is that generally speaking you do not need the
> common,
> > and for HD motors most of the times there is no sensor therefore you
> should
> > look at the sensorless notes I think. If you look for sensored motors
> you
> > should be able to get one from CD ROMs.
> >
> > For the basics MC app notes are definitely good sources, you can even
> find
> > one with digital filtering the back EMF (you will see what is that). I
> think
> > there is even a controller written in assembly, so should be fun.
> >
> > Tamas
> >
> >
> >
> > On Thu, Apr 10, 2008 at 4:55 PM, Nicola Perotto <nicola@nicolaperotto.it
> >
> > wrote:
> >
> >
> >> Hi all,
> >> i have a harddisk motor and want to control it.
> >> The motor is brushless but have 4 wire, the fourth is  a common.
> >> I haven't found anything in the internet about this... any suggestion?
> >> Thanks
> >>      Nicola
> >>
> >>
> >> --
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> >
> >
> >
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