Re: [CAD_CAM_EDM_DRO] LPT question from newbie

Hunter,

Are you sure that the port is correctly addressed? Might check it in
the BIOS setup routine.

Also, check the voltages on the output pins in both the logical high and
low states -- some of the more modern printer ports run at only 3.3
volts and might not have enough oomph to run the interface card reliably.

If the control board has all the relays on when it is not even plugged
into the computer, then that suggests you are working with active high
outputs, and that the parallel port is unable to pull the control lines
close enough to logic zero to turn off the relays, or that you are not
addressing the proper port number.

If the control board has all the relays off when it is not plugged into
the computer, but then the relays turn on when plugged into the PC, then
it indicates the presence of active low input lines, and that your
computer is unable to pull the pins low enough to get then to shut off,
or again that you are not properly addressing the LPT port. This would
require a buffer chip or transistor to assist the port output line to
adequately drive the control board line to a logic zero level.

HTH,

Dave


hunter_print wrote:

> I was hoping someone could help me with this. I use a PMDX-120 to
> isolate the computer I'm working with. When I plug it into a computer
> at work, Relay A is off, the rest are on. When I plug it into a
> computer my school provided, ALL relays are on. This is most
> distressing since I am using Relay A to power a VERY small motor
> (ON/OFF, no speed control) I can't change the state of the relays that
> are on when plugged in.
>
> This all leads me to believe the pins on LPT1 that control these relays
> are active. Am I configuring something wrong? Is this a problem that
> can be fixed in TurboCNC, or is this something to do with the computer
> itself? The computer where I work is an old Gateway 4DX2-66 with the
> printer port in $3BC. The school computer has been stripped down so
> that only DOS runs on it, but it is a newer model (5+ years) pentium.
>
> -Hunter