Date   : Fri, 23 Dec 1988 02:18:55 GMT
From   : caesar.usc.edu!mlinar@oberon.usc.edu (Mitch Mlinar)
Subject: floppy shut downers

In article <1080@pilchuck.Data-IO.COM> del@pilchuck.Data-IO.COM (Erik Lindberg)
writes:
>
>Wow! Mitch talks about some horrendous circuit using a basement full of
>components just to turn a drive motor on & off!   :-) :-)
>
>   ... circuit details ...

Your circuit makes me think you misunderstood, so a few comments:

(1) You assume the 8-inch drives have a motor control line.  No
early 8-inch drives have such a puppy.  In fact, most newer ones don't
either.

(2) The change has been to go from AC motors (on the old 8" drives) to DC
motors with built-in motor control.  My circuit is for AC.  Using a relay to
control two 8" 120v AC drive motors should introduce some nice backward
current which will help destroy your relay contacts, not to mention the noise
introduced by same.  However, it can be done as you suggest provided the
appropriate feedback diode and capacitor are added.

Call me biased, but I happen to hate moving parts which means I use a
mechanical relay as a last resort. :-) :-)

(3) Finally, the Xerox computer has no motor control line.  Period.  Not even
for 5.25" drives.  5.25" drives have to be strapped for "motor on select"
rather than using the "motor control" line.  Of course for this, you don't
need any circuit.

Otherwise, I see no problem with your solution.

-Mitch