*** Ideas needed for developing interactive displays....

[Tony Duell]

> 
> On Tue, 2004-09-07 at 11:03 -0400, David V. Corbin wrote:
> > >>> Jules, yes a large hard drive seeing would  be  very  
> > >>> interesting.  <snip> ....  the size of a washing machine but 
> > >>> all glassed in top...  lots of power lots of heat......
> > 
> > While I have not been following every message in this thread..It seems like
> > a replica might be the best way to go. Could definitely "play some games" to
> > make it more reliabile, lower-power, etc. Whould stilll give the look and
> > feed of the classic drives [oh how I remember a row of RP-06's spinning
> > away!]
> 
> Yep - I was going to do this with a more modern drive (5.25") and stick
> it in a wall-mounted cabinet along with a keypad and display (I've got
> some nice vacuum-fluorescent 7-segment displays lined up for the display
> bit).
> 
> I'm hoping I can replace the drive's cover with a homebrew perspex one
> without too much crud getting in - data reliability isn't important but
> I'm not sure how reliable any embedded servo information will remain.

Pick one of the stepper-motor drives -- they don't have servo information 
to worry about!. Some of them, Rodime being one that I remember. do still 
take _some_ information off the platter (like the position of the index 
pulse -- the hall sensor generates several pulses per revolution, it 
takes a single pulse from the disk at power-up to determine which of them 
is the index), but I guess you can find one that doesn't actually need to 
read anything. 

> 
> Other option is to drive the head voice coil directly - in theory that
> bit's not too hard, but a lot of drives are clever enough to shut down
> the spindle motor if something's amiss (such as the heads not responding
> to movement from the logic!). I'm not sure how easy it'd be to work out
> how to drive the spindle motor.

Try an ST506 or ST412. Certainky on the latter the spindle motor driver 
is a separate PCB, and the _only_ connections to the rest of the drive 
are +5V and ground. That's also a stepper-motor drive... Can you find a 
dead/dying ST412?

-tony