hard drive stepper motor driver

[steev]

hello all,
i have a stepper motor salvaged from old hard disk drive.i want to use this motor in some applications like propeller clock,LED pov etc.for which the motor shld be running contineously.while googling i found below ckt.
**broken link removed**
**broken link removed**

i have some doubts in the circuit.
the ckt maker said

Basically to get it going you start it at the lowest speed and slowly ramp it up with the potentiometer.

that means every time i have to start the motor slowly at low RPM?
and what shld be the value of "BUZ11 N-CH FET"
what max voltage i can feed to this ckt?

 

[Hero999]

Your hard disk uses a stepper motor right?

Therefore it must have a stepper motor driver. I would start by Googling for the chip part numbers near the stepper motor on your hard disk and build a driver from them.

As far as your questions regarding this circuit.

that means every time i have to start the motor slowly at low RPM?

Yes, you do, but it depends on how slowly, you might be able to replace the 10k pot with a 100uF capacitor and 10k resistor in series, the capacitor charging slope will gradually increase the duty cycle untill the motor is 95% on.

what max voltage i can feed to this ckt?

Well the author states they've never tested it above 5V, but look at the datasheets of the componants for a clue; these can be found using Google.

and what shld be the value of "BUZ11 N-CH FET"

well if you need to ask this then you really need to learn more, try Googling for "BUZ11 datasheet" and use a MOSFET with a similar specification.

My final question is do you actually know how this circuit works?

 

[steev]

sorry i shld have red wikipedia about stepper motor first.
now i have some idea abt them.
and abt getting controller from hard disk itself i'll try that.

 

[Nigel Goodwin]

Are you sure it's a stepper?, is it from a really, really old hard disk - 5 or 10 megabytes only?, and pre-286 computers? (and certainly NOT IDE) - anything remotely 'recent' won't use a stepper motor.

I've used stepper motors from old 5-1/4 inch floppy drives, they work quite nicely and are easy to use.

 

[steev]

I've used stepper motors from old 5-1/4 inch floppy drives, they work quite nicely and are easy to use.

why motor from HDD is they are quite at high RPM.is it possible with floppy motors.and what ckt did u used to run that 5-1/4 floppy motor..

 

[Nigel Goodwin]

why motor from HDD is they are quite at high RPM.is it possible with floppy motors.and what ckt did u used to run that 5-1/4 floppy motor..

The stepper is for moving the heads, not for spinning the disk - the stepper just requires four drive transistors and the correct sequence, but it's too slow for a propeller clock.

If you're looking at the spin motors?, then they are usually DC brushless designs - and a LOT more complicated to drive without the IC that's designed for it.

All you really need for a propeller clock is a standard DC motor.

 

[dreadknought]

The stepper is for moving the heads, not for spinning the disk - the stepper just requires four drive transistors and the correct sequence, but it's too slow for a propeller clock.

If you're looking at the spin motors?, then they are usually DC brushless designs - and a LOT more complicated to drive without the IC that's designed for it.

All you really need for a propeller clock is a standard DC motor.

Do you think it's possible to tap into the motor-drive IC outputs to determine the approximate position? With some trial and error, you could program a microcontroller to sense the position based on the outputs of the motor-driver, and create some nifty projects like the LED hard drive clock I've seen going around, but without using a hall-effect or optical sensor.

Any ideas?

 

[Boncuk]

The stepper is for moving the heads, not for spinning the disk

HDDs don't use steppers for the R/W-heads - far too slow. They have a very strong permanent magnet and a coil being deflected (mounted to the R/W head on a swivel) without any gear in between.

Better to use 3 1/2 or 5 1/4" floppy R/W-motors which are used together with a precision worm gear.

Make small generators easily, too.

Hans

 

[Nigel Goodwin]

HDDs don't use steppers for the R/W-heads - far too slow.

I know, that's why I specified steppers from a 5.25 inch floppy drive.

Nice strong magnets in duff HDD's though!

 

[Boncuk]

I know, that's why I specified steppers from a 5.25 inch floppy drive.

Nice strong magnets in duff HDD's though!

Drill a hole and fix a wire to it. Then stick it up your fridge. Makes moving easier.

 

[Nigel Goodwin]

Drill a hole and fix a wire to it. Then stick it up your fridge. Makes moving easier.

A friend at work took some to the pub and did tricks with them - they work really well even through a thick table!

 

[mashersmasher]

i know that on an older hard drive the motor would spin up once i touched the first few pins on the ide port but it would run for a period of time and stop. if you had a 555 opening and closing the circuit on the pins it could keep it running.

 

[Bear_2759]

on newer HDD's Isn't the motor for the platters a stepper motor? as far as I know they are and always have been? I'm only young so "always" is mabey 10 or so years

I get plenty of dead HDD's for various reasons at work so I was thinking of building some kind of robot out of the stepper motors

my immagination was going wild and I was thinking of a robot spider, 3x stepper motors per leg... total of 24 stepper motors... but I think that would be a little over the top for a starter project.

 

[3v0]

No. They are brushless DC motors. A computer is used to energize the coils at the correct time which varies with speed.

Your initial project sound a lot too complex for a first.
But not knowing your background it is difficult to tell.

3v0

on newer HDD's Isn't the motor for the platters a stepper motor? as far as I know they are and always have been? I'm only young so "always" is mabey 10 or so years

I get plenty of dead HDD's for various reasons at work so I was thinking of building some kind of robot out of the stepper motors

my immagination was going wild and I was thinking of a robot spider, 3x stepper motors per leg... total of 24 stepper motors... but I think that would be a little over the top for a starter project.

 

[Dean Huster]

There some repetition in my comment, but bear with me.

Most any HDD made since 1980 has no steppers at all. Head positioning is via a "voice coil" circuit. A stepper would be too sloppy, be too slow (horrid access time), and not have enough steps, even with gearing to handle all of the cylinders (tracks) on a HDD platter ... and if geared, the gearing backlash (play or slop) would eat the designer alive. Spindle drive is via a brushless motor.

On floppies, the head positioning was via a stepper because there are far fewer cylinders on a flexible diskette.

Nigel mentions the rare earth magnets used in the voice coil drive of a HDD. They are powerful enough that they can be dangerous. Let to of them be attracted violently to each other and they can easily shatter. If the tip of your finger is too close to the gap between two rare earth magnets, they can easily pinch a blood blister on it when they slam together. Two of those magnets that are "attached" to each other are very difficult to separate. And you can screw up the paint job of the refrigerator door or a steel-clad passageway door trying to get them off. Get one to close to a CRT monitor or TV screen and you'll have to degauss the thing ... and I understand that sometimes they can permanently damage the shadow mask. They're great magnets for demonstrating magnetic induction of current in a wire.

Dean

 

[Grossel]

Most any HDD made since 1980 has no steppers at all. Head positioning is via a "voice coil" circuit. A stepper would be too sloppy, be too slow (horrid access time), and not have enough steps, even with gearing to handle all of the cylinders (tracks) on a HDD platter ... and if geared, the gearing backlash (play or slop) would eat the designer alive. Spindle drive is via a brushless motor.

A little comment to that. It is fully possible to position a stepper at any position between two steps. It is possible if the voltage to each coils to the stepper can be adjusted independently.