From: Ulrich Peters
Subject: Re: Urgent help needed to blank monitor
Date: Tue, 5 Nov 2002 11:02:15 -0200
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I think it might be best to expect a certain bit pattern on the parallel
port, to get one logical high (or low) to control the circuit, because
the serial port is already in use by a bill acceptor, and the sound card
is used to provide acustical feedback to the user during the normal
operation of the software.
Although a 555 timer could be used to create a delay to switch on the
monitor, I prefer to use the parallel port solution, because I would
have control over the shutdown process as well. The equipment has a
button on its back to power down the equipment. Before my software shuts
down, the last thing it could do is quickly send a new byte to the
parallel port, turning off the monitor, before Windows shows its usual
shutdown dialogs ("saving settings", "closing connections", etc.).
Unless you send new data to the parallel port, the last byte sent
If somebody could just tell me how to control the coil of a 5V reed
switch, probably using a simple BC5xx transistor and a couple of
resistors, controlled by a logical H or L of the TTL output - I think
then I would have all I need. Could you specify this circuit?
Thank you again,
In article , info@pcs-nooo-spam-
> A solution requiring no hardware modifications inside of the PC case
> might be preferred. He could get the 5V from one of the ports.
> Another solution would be to play a DTMF sound (if this PC has a sound card).
> A simple DTMF decoder could than turn on the monitor.
> You could even setup windows to play that particular DTMF (wav) upon bootup.
> > Yes, and the duration (and sometimes the states) is consistent each time
> > it boots. I'm thinking it might be easier and just as effective to use
> > a 555-timer configured as a one-shot to provide a delay equal to a bit
> > more than the computer's boot time. Just trigger it from the +5V power
> > to the mobo and have it operate a relay on the monitor's input power.
> > Someone already suggested this, and I think it may be best.