Re: breakout board and diode question

thanks for your reply,

did you ever build a breakout board that utilizes the 74LS541?
do you have or know of any diagrams of how to build a breakout
board using that octal driver, keeping in mind i'm not an E.E.
but a really good assembler. haha

thanks again
jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <info@t...> wrote:
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "ja_erickson"
> <ja_erickson@y...> wrote:
> > Greetings,
> >
> > is it possible to protect the parallel port of a p.c. by
> > building a breakout board that utilizes diodes instead of
> > opto-couplers. i am interested in building a breakout board but
> > i dont have the electrical knowledge to design an opto-coupler
> > board. any suggestions or instructions on which components
> > to use sure would make my day.
> >
> > thanks
> > jeff
>
> If you put the diodes in series with the pins you will loose .6
volts
> and the port will not sink current (it won't turn on a load that
> requires an active low signal). If you put a diode from gnd to
each
> pin (anode to ground) it will work to supress negative going
spikes
> coming from the outside world, however most parallel ports have
that
> protection built in. Nothing you can do with simple diodes will
> protect you from overvoltage or excess current draw (if you want
the
> port to drive the load). A 5.6V Zener on each pin to ground will
> clamp any incoming voltages over the limit to ground and suppress
> negative spikes as well. Most of the problems we see with PP pins
is
> lack of drive or noise related issues. Your best bet is to use an
> active device like a 74LS541 octal driver that will isolate the
port.
> and "sacrafice" itself in the case of gross over voltage. The
opto
> couplers do more than just protect your parallel port since it
> separates the grounds of the two systems and reduces noise
> transmition on the ground wires. If you want the best solution
Optos
> are the answer.