Re: [CAD_CAM_EDM_DRO] Re: High voltage protection for a breakout board.

I'll add my two cents to this, if it's of value:

Optical isolation provides the system with immunity from grounding
differences, which can be quite catastrophic. I recall a computer
installation where a terminal was in a separate building from the computer,
and both the communications board in the computer and the terminal kept
failing. A tech finally measured voltages, and found a 30v difference in
ground reference between the two buildings. Bizarre, yes. Bad, yes. But
everything in both buildings worked just fine when isolated from each
other. An opto-isolation interface between the two machines worked
perfectly: no more problems.

In CNC applications, the motor start/stop changes and loading changes when
a tool moves through a cut induce large swings in current, which always
means fluctuations in observed voltage, since no conductors are perfect.
Opto's keep those fluctuations from becoming destructive to expensive
computers and the like.

Tom Harrison (been there, done that, and likes opto-bulletproofing)

At 5/4/2005 10:16 PM, you wrote:

>Hi Arturo,
>
>I don't know if you realize that optoisolators are not simply used
>to "protect the computer from high voltages that stepper drivers
>handle." Your original post also seemed to show a bit of a
>misunderstanding in this area as you were thinking a simple 74xx245
>buffer might be a replacement for an optoisolator because of its 2kV
>ESD protection. As I said, ESD is a minor consideration and has
>really has nothing to do with protecting the computer from anything
>going on with the motor. It has more to do with static discharge as
>what happens under low humidity conditions when someone walks across a
>carpet and decides to touch an exposed electronic connection.
>
>At the risk of repeating myself (please take this as constructive
>criticism), optoisolators are very useful for separating circuits
>entirely--include grounds. Sans an optoisolator, you risk making for
>an unreliable system if you join a digital signal ground with a noisey
>analog ground that potentially could also create ground loops. Even
>if you manage to have a system work on your workbench, you are only
>asking for trouble if you expect any arbitrary wiring or driver a
>potential user could use would work without intermittent/hard-to-find
>problems.
>
>Cheers,
>Adrian
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Arturo E. Duncan"
><aduncan@c...> wrote:
> > Alan,
> >
> > Opto-Isolation is to protect the computer from the extreme high
> > voltages stepper drivers handle(yes, I know geckos have opto-
> > isolators, there are other drivers that don´t).
> >
> > I understand your opinion with regards to breakout boards. I myself
> > have setup machines without them. But it makes things easier and
> > safer to setup. This breakout board I hope to price it the 20 to 30
> > range, making it affordable to any budget.
> >
> > Thanks,
> >
> > Arturo Duncan
>
>
>
>
>
>Addresses:
>FAQ: http://www.ktmarketing.com/faq.html
>FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
>Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
>Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
>Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
>List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...,
>timg@...
>Moderator: pentam@... indigo_red@...
>davemucha@... [Moderators]
>URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
>OFF Topic POSTS: General Machining
>If you wish to post on unlimited OT subjects
>goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to
>reach it if you have trouble.
>http://www.metalworking.com/news_servers.html
>
>http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
>sister site to the CCED group, as many of the same members are there, for
>OT subjects, that are not allowed on the CCED list.
>
>NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING
>THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
>bill
>List Mom
>List Owner
>
>
>Yahoo! Groups Links
>
>
>
>

[Non-text portions of this message have been removed]