Re: [CAD_CAM_EDM_DRO] Opto Isolation ??

> From: Hugh Currin <currinh@...>
> Life is good. I have two of three Camtronic 5A driver boards built and
> seemingly
> working. I also have a new PC running rtlinux and EMC. Did I say life is
> good? :-)

Congratulations!

>I am hoping someone will look at these
> and tell me if they will work or if not what modifications are needed.

What you've done looks pretty reasonable and would work fine for things like
spindle_on, and lube_level_low. If you plan on using this opto device for
something like the step signal, you might want to review the specs for rise
and fall times of the output. I believe that they listed the typical tr and
tf at 100uS. If that's really the case then your minimum pulse period would
be 200uS which means a max step rate of 5kHz. Compare these times with the
requirements of the chip you are driving on Dan's board such as max input
rise and fall times, and any setup or settling time requirements.

> Any other tips regarding this computer/driver connection?? Is such
> opto-isolation
> a reasonable approach?

You'll also need a separate DC supply for the switch inputs, and there can't
be any connection between the PC's ground and the DC ground in the machine.

I'm way less squeamish about directly connecting the PC to external circuits.
Instead of connecting your stuff to the built-in port on the motherboard, get
one of those $8 parallel port boards you plug into a slot on the PC and use
that. If you fry the $8 board, it's no big loss. Any failure catastrophic
enough to blow up the PC will probably kill you as well ;). Consider systems
using the Servo-to-Go board; they have all kinds of stuff like the encoders
and servo amp inputs connected to the STG board which is plugged into the PC
with no isolation at all.

Good Luck,
Matt