Re: Pullup resistor on a NC touch probe, Mach3?

Monte,

The input pins will normally float high by themselves. You can try to
hook it up with just the NC probe and no pullup resistor.

There is no danger involved with directly connecting your input pins
(10,11,12,13,15) to your parallel port common (pins 18 through 25).

If that proves unreliable, then you can pull it up with a pullup
resistor to a +5 volt supply. This is where you can damage your
parallel port. To be on the safe side you will need to install a
current limiting resistor in series. Here is a good tutorial on the
parallel port
http://www.epanorama.net/circuits/parallel_output.html#circuithow

Arnie