Re: High voltage protection for a breakout board.

Hi Arturo,

Unfortunately, these parts will do nothing to allow for separating
the grounds between the PC's parallel port and the controller.
While providing ESD protection is always a good thing, this is
really a fairly minor concern. PC parallel ports--from my own
experience--can be quite sensitive to ESD with nothing attached and
require careful handling anyway.

Note too, if you are confusing EMF with ESD, that problem is not
dealt with at this level anway; EMF is dealt with at the driver
level one step removed to prevent high voltages caused by collapsing
magnetic fields around motor windings from damaging the driver
electronics.

Other manufacturers would not use opto isolators (as I also have) if
they were not required. In practical terms, they essentially
isolate the circuits completely.

You might be able to have your circuit work for a given setup. But
if you are making this "for general use" as you say, you cannot
count on this working for any arbitrary setup for a user.

BTW, your link didn't work for me. Here's another:

http://focus.ti.com/lit/ds/symlink/sn74lv245at.pdf

Cheers,
Adrian

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Arturo E. Duncan"
<aduncan@c...> wrote:

> Group,
>
> I have been working a design for a new breakout board for general

use

> in cnc applications. The new design is based on the SN74LV245AT

IC,

> wicth acts as a bi-directional buffer and has ESD (Electro Static
> Discharge) protection for up to 2000V. I have been hoping to
> eliminate the opto-isolators with the use of these IC, and will
> greatly reduce the number of parts and simply assemble, thus

enabling

> the possibility to reduce the cost of the final product.
>
> I know for most interfacing applications this IC is a great

buffering

> device, but ¿would it be good enough protection from a possible
> failure of a stepper driver?
>
> The datasheet for this IC can be found at :
> http://www.cnc4pc.com/Tech_Docs/sn74lv245at.pdf
>
> Thanks,
>
> Arturo Duncan