Re: ParPort output low - hi-Z or ground? - file section

I had sent you an e-mail off list requesting you send me the files.

The files area is only accessable by the moderators and we are more
than willing to post pretty much whatever you want (as long as it
does not include bust enhancement or enlargement of other body parts)

Feel free to send it to my e-mail or to the e-mail on the groups home
page.

Dave




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ghidera2000"
<ghidera2000@y...> wrote:

> Hmm, for some reason I don't get any of the file commands in the
> files area. I've uploaded both versions of the optoisolation scheme
> to the Electronics_101 files area - A3977 Stepper folder. Thats
> where the schematic for my stepper controller is anyway. Have to
> change that to incorporate the optos (currently has 74245s) and add
> the EStop relays.
>
> Do the parallel port inputs have internal pullup resistors when
> they're high? Logically, I can't see them NOT having resistors, how
> would anyone manage to pull them low without burning the port pin?
> Then again, I'm no EE 8). As you can see on the drawing, I've just
> run the port pin through the transistor side of the opto and
> directly to ground. If I put a resistor in there, would I not just
> keep the voltage on the input high?
>
> Oh and thanks for the 3.3 volt tip. I checked mine and the outputs
> are 3.3v while the input high is a full 5v. Had to adjust the led
> resistors (7mA just ain't enough).