[Dr Doofensmirtz]

When adding a cycle start button to mach 3. What goes on the other end of the switch?

If it goes to pin 15???? input, do you use a 5+ volt DC source, or ground the pin to make it activate?

Thankx,

Heinz D.

[UUU]

You ground the pin. Note that this will be to the PC ground potential (on other parallel pins) which may differ from your machine ground.

[Al_The_Man]

You ground the pin. Note that this will be to the PC ground potential (on other parallel pins) which may differ from your machine ground.

Although on modern MB's the MB ground plane AND the PC power supply common is at ground potential, likewise, so is the parallel port 5v common.
At least this is what I have always discovered?
The usage of 'Ground' instead of 'Common' can be misleading.
Although your PP common may be at ground potential, Never use machine ground as a conductor.
Al.

[Dr Doofensmirtz]

So then, where would be the best place to get my ground from for this type of switch? If I find a pin that is common inside the parallel port, or the breakout board calls it common/ground use this?

Thankx,

Heinz D.

[Al_The_Man]

Pin 18 to 25 are normally 5v commons, you may have to confirm it with a meter check.
Al.