Re: [CAD_CAM_EDM_DRO] Simple parallel port wiring question

bgroover1 wrote:

>
> I just finished making the brackets for my home and limit swithes.
> When I wire them should they go back to pin one or pin 18 on the
> printer port. I've read some of the faqs on this and I think it
> should be pin 1 but just wanted to check.
>
> thanks,
> ben
>

Pin 18 is the ground. See my faq page at http://www.cncKITS.com
(halfway down) for a typical wiring scenario.

In this scenario, pin 15 is used for X,Y,Z limits and since the
microswitches are normally closed, the line is hauled to ground
(pin 18). But if any one of them is opened, the +5V floats the
line high through the pull-up resistor, and pin 15 senses that.

Be aware that another option exists: using normally open switches,
but I personally think NC swiches are safer (for limit and home
switching).

regards
Doug Fortune
http://www.cncKITS.com