Using HDD motor as generator

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Nigel Goodwin said:
I thought they were DC brushless motors?, with static coils and a permanent magnet rotor - no brushes, so how could they feed power to coils in the rotor?.
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The animation shown on the page linked to below review how:

Motor Control Switched Reluctance Motor Solutions By Freescale.

Just ask yourselv: Have you experienced that a harddrive spindle motor provided any voltage or current output when you aplies rotation speed? Don't think so. Not for any modern hardisk drive. Reason is as easy as this: No permanent magnets inside
 
I have an old hard drive motor in pieces right in front of me and it has magnets in it or more of a multi pole magnetic ring on the spindle to be exact. The odds are that there is more than one type of hard drive motor design in existence.

Still I doubt it would put out much power as a generator.
 
mazaldo, you're repeating my question already. Anyway use a meter and see the output, you'll save all the superfluous posts you can. Put an LED to the output terminals, it'll be good enough. If it can't even light up an LED, you'll never be able to charge the batteries unless you have a conversion circuitry, but that's another story.
 
alright well i tested it, and three of them read 5 ohms and one read 2.5ohms. (three phase)

I think i am going to try and find a stepper motor instead. it doesnt seem logical to try this when i know that it will not be very effective.

What kind of stepper motor should i look for that will be the most efficient and powerful for my application?

Matt
 
**broken link removed**

**broken link removed**

Alright guys i also had this laying around what you think?


its from a floppy drive i believe there are three terminals in the upper left corner in the pic with the cover off


matt
 
mygatt3 said:
I think i am going to try and find a stepper motor instead. it doesnt seem logical to try this when i know that it will not be very effective.
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Acording a paper I read some time ago (sorry to say I don't remember the title or source) said that reluctance motors was often used as generators in airplane engines. If that's true, I'm pretty sure it should be pretty efficient if you doing it right.


mygatt3 said:
Alright guys i also had this laying around what you think?
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It's probably a brushless DC-motor. It means that it has the controller circuit built in. You can always test with a screwdriver if it is permanent magnets inside.
 
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OK - I just took an HDD to pieces, it's a Seagate 160Gb, and the spin motor is pretty well built in the casing, so you can't see anything of it apart from the three wires coming out.

Connecting a scope to it, and spinning the motor with your fingers gives between 2 to 3 volts peak to peak between two of the three wires - so not a lot of voltage.

If you short out the same two wires and spin the motor again, it stops after a second or so, with out the short it spins for probably 5 or 6 seconds, so it's not producing very much power.

I think it would make a really useless generator.
 
I made a generator just a bit bigger than a standard HDD, it generates 30V at 3500 rpm, no load. Probably a DIY is much better.
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....and I used HDD neo-mags.. Well as the saying goes, when you can't eat lemons... make some lemonade out of 'em.
 
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do the rectifier upper proposed (6 diodes) and measure the output voltage.
HDD motor IS a 3 phase AC motor, WITH permanent magnets, so it will work as 3 phase generator too. (but I'm afraid that voltage generated is too low for your needs)
 
Nigel Goodwin said:
If you short out the same two wires and spin the motor again, it stops after a second or so, with out the short it spins for probably 5 or 6 seconds, so it's not producing very much power.

I think it would make a really useless generator.
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You'll probably need to spin it near it's operating speed to get a reasonable voltage, which is about 7200 RPM for a typical modern hard drive.
 
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