PDA

View Full Version : optocoupler; opto-isolater



dhprc2
06-02-2003, 11:40 AM
Hi,

From time to time I have read recommendations to use an optocoupler or opto-isolater between a CNC control card and the parallel port on the computer as a way of preventing potential damage to the innards of the computer.

Is there a commercial product available to perform this function or is it something I need to build myself?

Are there any instructions available on how to build such a beast?

Do any control cards come with this feature integrated on the card? It would seem to make sense to me...

Thanks for the help!

ToyMaker
06-02-2003, 01:19 PM
----------------------------------------------------------------------------
From time to time I have read recommendations to use an optocoupler or opto-isolater between a CNC control card and the parallel port on the computer as a way of preventing potential damage to the innards of the computer.
------------------------------------------------------------------------------

Yeah, always a good idea to isolate your computer from analog working voltages.

----------------------------------------------------------------------------
Is there a commercial product available to perform this function or is it something I need to build myself?
----------------------------------------------------------------------------

There is probably no general purpose circuit because there are so many possible variations and you probably don't want to pay for 25 lines of isolation when you are only using six.
Optocouplers are very simple, just an LED and a phototransistor in a dip. Digikey and Mouser stock them for cheap. There are even 2- and 4-in-1 packs.

----------------------------------------------------------------------------
Are there any instructions available on how to build such a beast?
----------------------------------------------------------------------------

Do a google for "optocoupler schematic", I got over 2000 hits and the first one has a .pdf schematic :) .

----------------------------------------------------------------------------
Do any control cards come with this feature integrated on the card?
----------------------------------------------------------------------------

All the more expensive controller/drivers have isolation built in.

robotic regards,

Tom