Tony Duell wrote:
Can you get at
any rotating part of the motor?
Simple enough to graft on your own hall-effect sensor...
YEs, and kludge on magnets to give the right number of pulses per
revolution with the right timing....
Timing and pulse count needn't be that important. You'd feed the output
from "your" sensor into a PLL to derive the
correct output frequency.
Of course at this stage, it's probably easier to build new hard drive
mechanicals from scratch. Seriously. Look at how cheap and attainable
CNC lathes are these days.
Gordon.