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Driving a HDD motor


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The BUZ11 is an ordinary Mosfet that needs 10V on its gate to fully turn on. Maybe a few in a bucket-full might turn on enough with only 4.8V. The 74AC14 has an output voltage only 4.8V.

You wouldn't need to test a bunch of Mosfets for a low threshold voltage if you use Mosfets designed for logic-level input voltage.

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After a little search I have found this small circuit that the author says it can drive a Hard Disk Drive Motor. Can anyone verify this please?
The site is: http://grant.solarbotics.net/Circuits.htm


The author has been using this circuit in excess of 2 years in robots he builds. I see no reason to rumor that it does not work.

MP
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The author has been using this circuit in excess of 2 years in robots he builds. I see no reason to rumor that it does not work.

MP



The author refers to this circuit as “very crude” which probably means that he is well aware of the fact that it can be significantly improved!
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This looks like it would run a little 3-phase motor at variable speed, continually. Such motors are used in hard disks to turn the platters, it is basically a small AC motor meant to run continually, and not really a stepper motor. Like other AC motors, it may likely have a lower frequency limit below which it will not be able to start or remain turning, and when stopped, there is little or no holding torque. 

The commonly seen stepper motors that are used for finely positioning things, have 2 or 4 coils that are driven with quadrature signals (90 degrees out of phase). However, hooking three of the 4 coils in such a stepper-motor might make it run, though somewhat unhappily here...

Also, there is the matter of the transistor threshold voltages that Audioguru mentions. Using a CMOS 4584 at 12V instead of the 74AC14 might work better. with the transistors shown.

Ashtead

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Sure, I agree this is a simple setup and that there are much more advanced circuits out there. OP stated that the author said it would work with a HDD motor and wanted to know if it was so. I am agreeing that there should be no problem in doing this. Author is clear on his site as to what motor this is for. Also, author has been using this design in his simple robot circuits for better than two years. Sounds to me like it is a bench tested design. Thus my statement, Why rumor that it will not work...  I see a lot of over-thinking functional designs on this site anymore..


MP

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I'm sorry that I have not reply earlyer but I was busy with my work.

I have problems in making the cirquit work.
I 'm testing the circuit in bredboard but it does behave like it should be.
I hear a sound like the motor is spining but in fact is sticked in one position. If I try to rotate it, it moves a little but after a while it stops again.
The measured voltage on mosfets is variable from 0-5V.
I have even try to power the motor with 12V but the result is the same.
By adjusting the 10k pot the "spining sound" changes frequency and I thing the torque of the motor to the oposite direction. Somewhere in the midle I get a smal kick of the motor of trying to get move but it freezes again.

The 4 pins on the back of the HDD are been tried with all the posible position combinations of power and 3 mosfets with the above results in only 2 combinations.

I'm not sure what I'm doing wrong here.

Thanks for the help and your interest!

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