Need Help!- optical interrupt input into parallel port??

[antichip]

Hello,

I am not sure if this is the right area to ask this but it is emc related.

I have an optical interrupt and encoder disk for it I am trying to tie into the parallel port. I'm sure it is a 5v unit.

More specific to this group, can I read this pulse off the parallel port for spindle speed control? I have an allen bradley VFD that I am going to try controlling using the pwm output of the parallel to control speed.

so what do ya think?

[Zig]

I am not sure I understand Your posting correctly but it seems like you have two separate questions
One is how to read interrupter signal via parallel port ...
The other how to drive a variable frequency drive which presumably looks for some kind of analogue control voltage...

Both need further clarification ... But let me look at the second point first.

The PWM output is available via LPT port pin at TTL levels notionally.
You will need to build a buffer to convert the PWM output into analogue voltage of appropriate scale to match the analogue signal required by your VFD unit.

On the first question.. sorry can not comment other than to say yes it is possible but need to understand your interrupter signal polarities and from where the interrupter is drawing its power.