On Tue, 2002-02-05 at 14:44, Anand Dhuru wrote:
> There's an interesting idea I saw in the Elektor magazine.
>
> When a PC (ATX SPMS) switches off, or hibernates,, the monitor still keeps consuming some power. Now, in this situation, it seems the +5V on the game port switches off as well. So, drive a relay by this voltage, and power up your external peripherals like the monitor, printer, mains powered speakers etc. thru' the relay contacts. A truly green PC!
>
> My question is, what is the maximum current one can draw thru' the 5V available on the game port?
>

I have just done the same thing, but used the USB port.  The solution I
adopted was one designed in an Electronics Magazine (don't remember
which).  This is really simple: MOC3021 + Triac.  I was worried that the
Triac would get hot, but the unit powers my monitor, speakers, laser
printer, hub and a few other odds and sods without getting hot and
without a heatsink.  The circuit is trivial - one current limiting
resistor into the DIAC and an RC snubber network on the triac.  Works
fine for my piddly non-inductive load!  I don't have the data sheet for
the opto isolator here, but I'd punt on only 20ma or so drain on the
USB.

Of course, if you DO plan high power devices the TRIAC power dissipation
could be a very serious problem..

/Kevin
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Kevin J. Maciunas              Net: kevin@cs.adelaide.edu.au
Dept. of Computer Science      Ph : +61 8 8303 5845
University of Adelaide         Fax: +61 8 8303 4366
Adelaide 5005 SOUTH AUSTRALIA  Web: http://www.cs.adelaide.edu.au/~kevin
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