Hi all, i need a motor with a high rotational accuracy, so i 've think
to re-use a
motor of a hard disk.
Here are some questions:
1) considering the smallest rotation permitted with a motor from an
hard
disk, which is the corrisponding rotating angle?
2) Does someone have any information about how to drive an IDE or S-
ATA Hard
disk using a parallel port ?
Can someone provide informations also about how to use voice-coil
control
systems ?
Any help will be appreciated.
Best regards,
Andrea
"Andrea Mazzolari" <andrea.mazzolari@gmail.com> wrote in message
news:1182685430.657139.130100@u2g2000hsc.googlegro ups.com...
> Hi all, i need a motor with a high rotational accuracy, so i 've think
> to re-use a
> motor of a hard disk.
>
> Here are some questions:
> 1) considering the smallest rotation permitted with a motor from an
> hard
> disk, which is the corrisponding rotating angle?
> 2) Does someone have any information about how to drive an IDE or S-
> ATA Hard
> disk using a parallel port ?
>
> Can someone provide informations also about how to use voice-coil
> control
> systems ?
>
Hi Andrea.
Some help here.. http://www.epanorama.net/circuits/diskstepper.html
On 24 Jun, 12:43, Andrea Mazzolari <andrea.mazzol...@gmail.com>
wrote:
> Hi all, i need a motor with a high rotational accuracy, so i 've think
> to re-use a
> motor of a hard disk.
Well, HDD motors aren't _that_ well regulated. Look into the way data
is laid out on disk and you'll notice areas set aside specifically to
record the speed the disk was turning when that area of disk was
written. It might not very that much but it's enough to make a
difference in this context.
> Here are some questions:
> 1) considering the smallest rotation permitted with a motor from an
> hard
> disk, which is the corrisponding rotating angle?
That depends. If it uses steppers then I doubt they'll be high
resolution types. Typically 90 degrees, or 45 degrees if you combine
two distinct stepper control methodologies.
> 2) Does someone have any information about how to drive an IDE or S-
> ATA Hard
> disk using a parallel port ?
Commercial adapters for this are available. I suggest you use them as
it isn't a straightforward pin x to pin y arrangement. Even the
software by itself to control such a beast is ambitious for a hobby
project.
> Can someone provide informations also about how to use voice-coil
> control
> systems ?
What is you are trying to do? First of all you make an observation
about the motors, but then you ask about driving disk units in
general. Now you are asking about voice coils which bring in another
area entirely. It would be helpful if we understood what the ultimate
goal was.
I need a system to make small rotations.
In a first istance i belived that motors in a HDD are step-motors. Now
i discovered that they just spin at a fixed speed, so they will be not
useful for my purpose.
In my understanding of voice coil motors, the permit very small
rotations, is this correct ?
Andrea Mazzolari wrote:
>> What is you are trying to do?
>
> I need a system to make small rotations.
> In a first istance i belived that motors in a HDD are step-motors. Now
> i discovered that they just spin at a fixed speed, so they will be not
> useful for my purpose.
>
> In my understanding of voice coil motors, the permit very small
> rotations, is this correct ?
>
> Best regards,
> Andrea
>
On 24 Jun, 23:46, Andrea Mazzolari <andrea.mazzol...@gmail.com>
wrote:
> In my understanding of voice coil motors, the permit very small
> rotations, is this correct ?
No. Voice coils make reciprocating rather than rotary motion - they
go back and forth instead of round and round. You were probably on
the right track with steppers to begin with. Steppers internally
always operate on the basis of 90 or occasionally 45 degree steps, but
many have built in gearing that effectively reduces the size of each
step to three degrees or so on the output spindle.
The other possible alternative is to use a servo if you need exact
rotational positioning. Servos don't allow continuous rotation in one
direction or the other, only through an arc of maybe 200 degrees,
although of course the precise size of that rotation may be modified
with gearing. The advantage of a servo is that it has a built in
knowledge of what position the axis is in, what position is desired,
and the circuitry to make the former the latter. This is true even if
some external force attempts to over-rule the servo: a stepper would
lose all knowledge of its position in that instance.
Servos are often used to control RC models and you should be able to
get a basic type for about $10-15. They are controlled using pulse
width modulation - sending a logically high voltage periodically to
the servo to indicate the position. A 1ms long pulse indicates one
extreme of travel, 2ms the other, and 1.5ms the centre of travel.
Doubtless you can find more details on the web.
On 25 Jun, 19:37, Andrew <andr...@sdf.lonestar.org> wrote:
> Servos are often used to control RC models and you should be able to
> get a basic type for about $10-15. They are controlled using pulse
> width modulation - sending a logically high voltage periodically to
> the servo to indicate the position. A 1ms long pulse indicates one
> extreme of travel, 2ms the other, and 1.5ms the centre of travel.
> Doubtless you can find more details on the web.
Just a clarification that comes to mind on re-reading this post.
Servos are continuously adjustable, it isn't a case of only three
positions being possible. For example, a 1.55ms pulse would indicate
just off centre in the same direction as that taken for a 2ms pulse.
This is analog electronics so at least in theory there's no limit to
how high the resolution can be.
On Sun, 24 Jun 2007 11:43:50 UTC, Andrea Mazzolari
<andrea.mazzolari@gmail.com> wrote:
> Hi all, i need a motor with a high rotational accuracy,
> so i 've think to re-use a motor of a hard disk.
Rotational and linear stepper motors are available in
many varieties. Another product type that might also
be
suitable would be a positioning system. Depending on
your needs a linear to rotary conversion might be
useful.
I'd have to have some idea what your positioning needs
are to look up specific solutions. How accurate to do
need? What speed is required? What load factors are
involved? I presume that price is also a concern.
Hard disk motor 
Linear Mode
