Re-purposing hard drive spindle

Discussion in 'General Electronics Chat' started by vortmax, Nov 1, 2012.

  1. vortmax

    Thread Starter Member

    Oct 10, 2012
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    I'm working a project that will use a hard drive spindle to hold a high speed rotor to drive a small generator. If I could just use the spindle motor as a generator, it would greatly simplify the project.

    I've looked this up online, and the main consensus is that unless you spin it at operating speed, you won't get enough power to do anything, but no mention of how much power that is. I should have no problems hitting 10 to 20k RPM with this, so spindle speed is not an issue. I just need to know if I can squeeze enough power out of this to run a micro, some stepper motors and some solenoids.

    Oh course I plan on building a prototype and testing it, but I would like to have some idea of what to expect before I get that far in.
     
  2. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Sorry, who actually drives what? Maybe Bedini, Zapata, Watson?

    Yes, 10 to 20K RPM seem not hard to get.
     
  3. vortmax

    Thread Starter Member

    Oct 10, 2012
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    I'm building a Tesla turbine. The spindle will be brought up to 10 to 20k rpm with compressed air. I'm just trying to figure out how much power I can coax out of the spindle motor if I run it as a generator.
     
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Don't forget that since most HD motors are brushless DC motors, the output will be three phase AC.
     
  5. vortmax

    Thread Starter Member

    Oct 10, 2012
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    yep. well aware. Should be simple enough to rectify. I'm also counting on that so I can use the wave form as an input to a closed loop speed controller.
     
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    I may not be smart but what could drive a HDD motor if u could spin it at 10K.

    Did u ever think about the power of the spindle it self.
     
    Last edited: Nov 2, 2012
  7. vortmax

    Thread Starter Member

    Oct 10, 2012
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    I'm spinning the platters with compressed air and using the motor as a generator to produce electricity. I'm using that electricity to power the micro, some stepper motors and some solenoids.

    I just did a quick and dirty test. I have a very old SCSII drive that I pulled apart. I simply hooked up two (out of 4) of the wires to my scope and gave it a spin...it produced a nice sine wave of a few hundred mV. So I played around a little and got it up above 3V with a 1 ohm resistor on 20psi of air, so just north of 9W. That was with non vented discs and me directing the nozzle by hand...and I could hear that the platters were struggling to hit speed. So I think I can probably hit 15 to 20W once I optimize the design and boost the air pressure.
     
  8. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    no kiddin...!

    Are u saying u can get couple of amps out of tht thing. No way hozay ( am I saying this right ?).

    You have to show it to me to make me believe it.
     
  9. vortmax

    Thread Starter Member

    Oct 10, 2012
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    I'll take some pictures. I was rather surprised as well
     
  10. vortmax

    Thread Starter Member

    Oct 10, 2012
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    Pictures attached.

    picture 1: Oscilloscope screen. This is the output with a 1 ohm load. I didn't have someone to help me, so I had to let go of the air source and grab the camera. In that few seconds, the drive had spun down, but 1.6V with 1 ohm load is 1.6A. Peak voltage I hit was again just above 3V.

    picture 2: Connections for test. I have a lead on 2 of the 4 terminals of the drive running to the 1 Ohm resistor. The other leads are running to the oscilloscope.

    EDIT: I started a new project thread and reposted the pictures. There was no sense in keeping two copies on the server so I deleted them from here. The new thread is: http://forum.allaboutcircuits.com/showthread.php?p=538776#post538776
     
    Last edited: Nov 2, 2012
  11. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Son of a gun !

    Start a new thread in the project forum.

    I bet u had to make a turbine inside the HDD
     
  12. BillB3857

    Senior Member

    Feb 28, 2009
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    In industry, it is fairly common knowledge that compressed air is one of the most expensive utilities in a plant. What is your source that makes it feasible to derive power from a hard drive spindle motor? Or is this one of those things just to see if it can be done?
     
  13. vortmax

    Thread Starter Member

    Oct 10, 2012
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    Just to see if it can be done. We have a dry air source plumbed to the lab which I'm using to test, but the final project will run off a bottle away from easily available power sources. The rest of the build is using compressed air as well (to play an instrument), so it was sort of fitting to use compressed air to both play the instrument and power the control system.

    In practice, the turbine could be run off of high pressure water or steam as well, so it is also a proof of concept for other applications.
     
    Last edited: Nov 3, 2012
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