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- Jimmy Neutron
September 21, 2008, 2:31 pm
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I've put some simple electronics to turn a on a light when the pc is turned on. I
am uses LPT port to to find out (a couple of relays & such) to turn the light on.
Unfortunately LPT ports power turns on and of a few times before the boot inget
around this problem? Tried USB but it has the same problem.
Re: PC uses LPT port to turn on light - problem at boot time
Jimmy Neutron wrote:
If you connect to +5VSB, that would be active whenever the switch
on the back of the computer is engaged. I don't think you want
When you push the power button on the front of the computer,
the power supply main outputs should come on. +5V would be
one of those outputs. You could extract +5V from a hard
drive connector. The voltage should be "solid" for the
length of your computing session. When you put the
computer to sleep (standby suspend to RAM), then the
+5V is turned off. That one shouldn't blink out, because
if it did, your computer would crash.
It is possible the power on the ports, like the ones
you've tested, is controlled by a switch (MOSFET) on the motherboard.
That may be for the purposes of "backfeed cut", or preventing
an external source of power from leaking back into the
computer. I cannot say anything about that with respect
to my own computers, as I've never tested for it.
I suspect if you use a disk drive connector for the function,
you'll get better results.
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