Parallel Port Interface cards

Hi everyone,

I've been evaluating a few parallel port interface cards and I'm finding a
real disparity between how they all work or how they are wired.

I've run into this issue because I connected the Electronic Lead Screw
spindle sensor onto PIN 13 of the interface card and did not see the index
pulse. Turns out this particular card has a 1K pull up resistor on the line
that the opto sensor has no hope of pulling down to 0 volts.

Grabbed a different Isolated card and this one expects whatever is driving
it to sink 12 milliamps. Again, not a chance with the spindle index opto
sensor.

The other anomaly is the various flavours of DB25 connectors. I've always
thought that most devices that plug into the parallel port usually have a
connector that mates with what's on the back of the PC. So since the PC has
a female DB25S it only makes sense that the device plugging into it would
have a male DB25P. All the various dongles that I have for In Circuit
programming EPROMS or FPGAs, DSP interface modules, Dongles for parallel
port to CAN bus, even dongles for software security all fit directly onto
the parallel port connector without an adapter cable in-between. Or in the
case of the security keys, often between the port and the printer with a
Male on one side and Female on the other.

Seems not so though for various parallel port interface cards. Some have
two female connectors that require a male to male cable and then male to
whatever on the other end. If you wanted to swap out the interface card you
might have to dig out yet another cable.

Perhaps I could get some feedback from others as to what exactly is out
there. If you've put some sort of CNC system on your lathe, what are you
using for a spindle speed sensor? Does it go directly into the parallel port
or is it powered and provides a strong signal?

Does the parallel interface card you are using create a high signal or a low
signal when nothing is plugged in?

Any other comments about interface cards?

Thanks

John Dammeyer