[Beowulf] Re: Emergency Power Off

Jim Lux James.P.Lux at jpl.nasa.gov
Tue Mar 20 12:40:07 PDT 2007

At 04:24 AM 3/20/2007, Robert G. Brown wrote:
>On Mon, 19 Mar 2007, Jim Lux wrote:
>>At 03:19 PM 3/19/2007, Robert G. Brown wrote:
>>>On Mon, 19 Mar 2007, David Mathog wrote:
>>>>After looking at the specs I believe that at least 4 of the 5
>>>>can be wired to shut down instantly.  (Not sure about the one
>>>>desktop size APC unit in the room, as it isn't mine so I don't
>>>>have the manual). However it seems that turning off the
>>>>tripp-lite UPS requires a positive voltage (12V) on the
>>>>inverter shutdown line.  Which means, that even after the
>>>>power has been killed (overtemp, red kill button,
>>>>or building power shut down) the fireman entering this room would
>>>>still need to smack another (not yet extant) red kill button, and
>>>>that button is going to need DC power in order to work.
>OK, this and David's replies are well worth preserving in marble and
>bronze somewhere.  I will dutifully spec out and assemble one as per the
>instructions below, and let my electrician friend do that last itty bit
>of wiring it in (or at least, wiring in the 120 line to drive the power
>So, if the same kill switch controls the supply breakers, is this
>accomplished by just replacing the box breakers with special ones that
>can be tripped by the control lines?  Sort of like a GFCI breaker with
>an extra wire where you can feed in a deliberate imbalance high enough
>to trip it?

That's called a breaker with a "shunt trip"

Another way is just to wire a contactor in series and power it 
through a NC set of contacts on your EPO.

>So with the resources you included I'll even try to answer this
>     rgb
>Robert G. Brown                        http://www.phy.duke.edu/~rgb/
>Duke University Dept. of Physics, Box 90305
>Durham, N.C. 27708-0305
>Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu
>Beowulf mailing list, Beowulf at beowulf.org
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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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