Paul Koning <paulkoning(a)comcast.net> wrote:
Does the tachometer have to be accurate, or does it just have to indicate
"spinning fast enough" to satisfy the spin-up logic?
It's not just spin up - the firmware monitors the disk speed all the time
But AFAIK the tachometer has nothing to do with how the bits are recorded
on the media. It's just there to be sure the disk is actually
If not, you could just use a 555 to generate a pulse
Maybe, probably, but I'm not sure why you'd want to. That's way more
complicated than just fixing the tachometer sensor, and having the firmware
shut down the motor in the event the belt breaks or jams, or if the motor
brake (yes, it has a brake!) freezes, etc is an advantage. It's a fairly
big motor and a fairly (by PC standards at least) heavy disk - there's a lot
of mechanical energy there.