Parallel port pins typically are open collector (They can only sink current
to ground) with an internal pull-up resistor.
You will need to short to ground on contact or add an inverter to your
setup.
alan battersby
<alan.batter...@n
tlworld.com> To
"Enhanced Machine Controller (EMC)"
07/01/2009 11:42 <emc-users@lists.sourceforge.net>
AM cc
Subject
Please respond to [Emc-users] Need help please with
"Enhanced Machine probe electronics
Controller
\(EMC\)"
<emc-us...@lists.
sourceforge.net>
Hello everyone,
I thought that I would make a probe for my setup. My idea was to have
one fixed plate and one movable plate attached to the probe head. These
plates are initially in contact and move apart as the probe hits the
surface thus breaking contact like a switch. I built this and tested
away from the computer and it seemed to work ok, when the plates touch
the output is 5v dropping to 0v when plates are apart. But connecting
it up to pin10 of the parallel port of my laptop I found that when the
connection between the plates is broken the voltage only drops to 4.6v
and so emc doesnt pick this up as a trigger. Would someone please tell
me why the voltage does not drop to zero as I expected it too? Is a
switch insufficient for the task? I am fairly sure that I configured emc
correctly, however my knowledge of electronics is very very basic. Also
I checked the port BIOS settings which are ECP & EPP.
Thanks
Alan
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