Power controlers... on another note.

Josh Fryman fryman at cc.gatech.edu
Tue Jun 4 04:49:20 PDT 2002

> Are there inexpensive remote power control solutions
> available for use beowulfers?

for the record, you can build an equivelant for less than $10/node for 
non-bulk retail (radioshack-like) pricing, plus one small micro or another
machine to control the setup.

all you need is a 5A 110V DC-control relay.  the way this works is 
essentially wire the relay + outlet like so:

   110V gnd/netural ----------> to outlet
   110V hot -----> relay -----> to outlet
                   v   v  
   +V DC signal ___|   |______ DC Gnd

when you put a +DC signal to the relay, it will pass up to a 5A load.
these relays cost around $4.  toss in a $1 outlet, $1 worth of wire,
and you've got a little setup that's usable. (of course, you can go 
more A's for more $.  a 20A relay runs around $7.)

for a DC control signal, you can either hijack (for a few nodes) the 
parallel port outputs, or get a $10 PIC or HC11 micro with a bunch of 
digital I/O pins that you can drive.  

it's quite straightforward.


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