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From: isca@icaen.uiowa.edu (Iowa Student Computer Assoc)
Newsgroups: comp.sys.next
Subject: How to make your external HD power up with computer
Message-ID: <5244@ns-mx.uiowa.edu>
Date: 3 Apr 91 21:12:18 GMT
Sender: news@ns-mx.uiowa.edu
Organization: isca
Lines: 30


  With the nifty keyboard power switch, I found it annoying to have to
dig under my desk and power on my external HD so.... I fixed it up so
that when I power up or down my NeXTstation, my external HD does the 
same.  I thought others might be interested in this as it is a rather 
easy hardware hack.
  The way to do this is to attach a relay to the SCSI terminator power
lines on the SCSI interface.  I highly suggest that you use a solid state
relay so that you don't introduce spikes on the line. (I used a Potter &
Brumfield # SSRT-120-D10 available for $15.75 from Molstad Distributing
1-800-831-0932).  Attach Pin 26 of the SCSI interface to the + control
and pin 20 (GND) to the - control of the relay.  Then just cut the wire
from your power switch and put the load side of the relay between them.

  Finished product looks like:
                         ++++++++++++++++++++++           SCSI Interface
       Power Out --------|- 2 Load       + 3 -|------------ Pin 26
    (to power supply)    |         Relay      |
       Power IN ---------|- 1 Line       - 4 -|------------ Pin 20
    (from power switch)  ++++++++++++++++++++++


 -- Dave
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|  David Lacey                           | Try the ISCA BBS and Archives    |
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