Re: Parallel port isolation

Doug,
It would be wrong to say it can't happen, however I think if the circuit
is correctly designed and a good circuit board is used, the problem is
no greater than when a printer is connected.

Remember printers use stepper motors, and some of the heavy duty page
and line printers use very large stepper motors and no isolation, and
some of the older version pen plotters also used large stepper motors...

Stepper drivers are relatively slow devices, and putting an opto
isolator in each signal line is not problem except expense and board
size.

regards
Hans Wedemeyer
http://home.swbell.net/hans_w


"Harrison, Doug" wrote:

> The notion of using the Parallel port to control machinery has
> fascinated me
> for 15 years. However, as one who obeys speed limits and never uses
> stairs
> without holding on to the rail, I am naturally concerned about hooking
> my
> non-isolated parallel port I/O to an 80 volt amplifier controlling
> inductive
> devices.
>
> Has anyone experienced fried computer syndrome from stray currents in
> large
> stepper systems? I know this can be a problem with servo systems,
> usually
> from ground loops.
>
> Doug Harrison
>
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