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'[EE] RS-232 optical isolation'
2006\02\21@235924 by Mike Hord

picon face
Just wondering if anyone has a favorite IC which can be
inserted in between two RS-232 devices (say, a PC and
a battery powered device using a level shifter) and provide
optical isolation, or if I need to start laying out a board.

Mike H.

2006\02\22@045623 by Gerhard Fiedler

picon face
Mike Hord wrote:

> Just wondering if anyone has a favorite IC which can be
> inserted in between two RS-232 devices (say, a PC and
> a battery powered device using a level shifter) and provide
> optical isolation, or if I need to start laying out a board.

The only isolated RS-232 interfaces I've ever seen were circuits, not ICs.
So either grab your wallet or start layout out :)

Gerhard

2006\02\22@062916 by j

picon face
There is a NM232DD from C&D Technologies , 2 transmitters, 2 receivers for
RS232.Rather expensive ...
/jorgd

At 05:59 2006-02-22, you wrote:

>Just wondering if anyone has a favorite IC which can be
>inserted in between two RS-232 devices (say, a PC and
>a battery powered device using a level shifter) and provide
>optical isolation, or if I need to start laying out a board.
>
>Mike H.
>
>

2006\02\22@065635 by Alan B. Pearce

face picon face
>> Just wondering if anyone has a favorite IC which can be
>> inserted in between two RS-232 devices (say, a PC and
>> a battery powered device using a level shifter) and provide
>> optical isolation, or if I need to start laying out a board.
>
>The only isolated RS-232 interfaces I've ever seen were
>circuits, not ICs. So either grab your wallet or start layout out :)


I have a feeling that TI may have some isolated RS232 devices, derived from
the Burr Brown ISO1xx device line. I think I have also seen Maxim advertise
isolated chips. If this is a one off, I would try Maxim for some samples.

2006\02\22@090556 by alan smith

picon face
Maybe I missed something....but isnt it as simple as just using opto's to isolate?  I am doing that right now for SPI to talk to a AC monitoring chip.  If you convert to from RS232 then drive into an opto, should work...?

"Alan B. Pearce" <spam_OUTA.B.PearceTakeThisOuTspamrl.ac.uk> wrote:  >> Just wondering if anyone has a favorite IC which can be
>> inserted in between two RS-232 devices (say, a PC and
>> a battery powered device using a level shifter) and provide
>> optical isolation, or if I need to start laying out a board.
>
>The only isolated RS-232 interfaces I've ever seen were
>circuits, not ICs. So either grab your wallet or start layout out :)


I have a feeling that TI may have some isolated RS232 devices, derived from
the Burr Brown ISO1xx device line. I think I have also seen Maxim advertise
isolated chips. If this is a one off, I would try Maxim for some samples.

2006\02\22@094010 by Xiaofan Chen

face picon face
On 2/22/06, alan smith <.....micro_eng2KILLspamspam@spam@yahoo.com> wrote:
> Maybe I missed something....but isnt it as simple as just
>using opto's to isolate?  I am doing that right now for SPI
> to talk to a AC monitoring chip.  If you convert to from RS232
> then drive into an opto, should work...?

I will think you are correct. From Wouter's site there is a link
to a galvanic isolated Wisp628 and it is using two opto
couplers for galvanic isolation.
http://www.picbasic.nl/images/schema_galva-wisp2.gif

Regards,
Xiaofan

2006\02\22@094449 by Mike Hord

picon face
> Maybe I missed something....but isnt it as simple as just
> using opto's to isolate?  I am doing that right now for SPI
> to talk to a AC monitoring chip.  If you convert to from
> RS232 then drive into an opto, should work...?

Level shifting makes this a sticky wicket.  Compliance versus
compatability is the key: an RS232 compliant signal is a
bipolar signal, +3 -> +25 (or so) for a space and -3 -> -25 for
a mark.  MOST PC's will accept a 0 for a mark and +3 or
higher for a space.  I'm preferring to keep a compliant signal
for my own sanity in keeping these things in the field.

The big problem here is that this battery powered device is
most righteously interfered with by the power supply of (most?)
Dell laptops.  The very act of having the power supply
connected (even without the power cord plugged into the wall,
or even to the power supply) adds an untenable amount of
ground noise to the circuit.  If I can avoid making a
"snake-full-of-pig" cable for this, I'd like to, but I may need to
anyway, unless I can find a suitable isolation driver.

Maxim makes an interesting one that provides +/-50V isolation;
I don't know if that'll quite cut the mustard.  I'll check it out,
though.

Mike H.

2006\02\22@100012 by Wouter van Ooijen

face picon face
> > Maybe I missed something....but isnt it as simple as just
> >using opto's to isolate?  I am doing that right now for SPI
> > to talk to a AC monitoring chip.  If you convert to from RS232
> > then drive into an opto, should work...?
>
> I will think you are correct. From Wouter's site there is a link
> to a galvanic isolated Wisp628 and it is using two opto
> couplers for galvanic isolation.
> http://www.picbasic.nl/images/schema_galva-wisp2.gif

Note that the galvano-wisp uses PC827 optocouplers, which are I think a
bit slow to work reliably/guaranteed at 115k2.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2006\02\22@100301 by Eduardo Garcia

flavicon
face
Hello Mike,
   I suppose this article might help you. Look at the link
http://www.bb-elec.com/bb-elec/literature/232spop4.pdf.

Regards,
Eduardo Garcia


{Original Message removed}

2006\02\22@103923 by Mike Hord

picon face
That is perfect.  Exactly what I was looking for.

Thanks, Eduardo!

Mike H.

On 2/22/06, Eduardo Garcia <egnascimentospamKILLspamyahoo.com.br> wrote:
> Hello Mike,
>     I suppose this article might help you. Look at the link
> http://www.bb-elec.com/bb-elec/literature/232spop4.pdf.
>
> Regards,
> Eduardo Garcia
>
>
> {Original Message removed}

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