[Beowulf] Re: Emergency Power Off

Jim Lux James.P.Lux at jpl.nasa.gov
Fri Mar 23 09:41:46 PDT 2007

>I've been looking for an off the shelf EPO solution, but so far the only
>things I've found are for huge data centers.  Anybody know of a product
>in my size range, to control roughly 10 EPO shut offs?  There's a point
>where adding more switch blocks becomes a bit awkward.

Relays are your friend.
EPO switch has Normally Closed contacts (i.e. they open when you hit 
the switch)
Power flows through contacts to small relay with NO and NC contacts
(you can use DC or AC supplies)
relay contacts go to UPSes
Multiple relays can be paralleled.

It's "fail safe" because if the AC power to the relay system fails, 
the relays drop out, and turn off the UPSes.

>David Mathog
>mathog at caltech.edu
>Manager, Sequence Analysis Facility, Biology Division, Caltech

James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875 

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