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Repurposed Hard Drive Motor

posted Dec 17, 2011, 7:45 AM by Lewis Baumstark   [ updated Mar 25, 2012, 10:04 AM ]
At one point while building upChukk, I toyed with using a hard disk platter motor to power a horizontal spinner weapon (e.g., small saw blade).  It had a lot to recommend it -- low amps, flat profile, and a arbor that perfectly fit the jamb saw blade I bought at Home Depot.  At the time, though, I knew nothing about brushless motors and eventually gave up on that line of inquiry.

I've come back to it now after learning enough to be dangerous.  I managed to accidentally buy a brushless ESC (I forgot to check its ampere rating before buying and it turned out to be too low for the particular motor I intended) a while back and realized it would probably drive the hard disk motor.  So behold my experimental setup:

The components:
  • R/C receiver (black box, top left)
  • R/C transmitter (not shown)
  • hard disk motor (silvery circle)
  • 30-A brushless ESC (yellow thingie in the middle; yes, I know 30-A is WAY more than needed here, but I already had it)
  • 7.4-V LiPo batter (black box with "PowerEdge" on it)
Using this setup I was able to control the motor speed with the transmitter.

The biggest question mark was that the motor had four solder pads (see next pic) -- but a brushless motor only needs three for signal.  One of the reasons I used a terminal block to connect the ESC and motor was I needed a quick way to test out which pads were the correct ones.  The terminal block would let me re-arrange connections easily until I found the right combination.  Ironically I hit it on the first try.  :)

(My best guess as to the fourth solder pad is that it's for bleeding off static that builds up as the platters spin.  Static and hard disks are bad, mmm-kay...)

Finally, a pic with the saw blade attached: