Searching \ for '[PIC] What is wrong with PC serial port?' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/ios.htm?key=serial
Search entire site for: 'What is wrong with PC serial port?'.

Exact match. Not showing close matches.
PICList Thread
'[PIC] What is wrong with PC serial port?'
2007\09\23@131454 by mamad876

picon face

Hi all,

Following my last post about MAX232 and Caller ID decoder, thanks to all who
gave me hints and solutions on this. I redesigned all my circuits, now my
caller ID decoder using SM8223AP works well! It detects Caller IDs and also
dialed DTMFs as well, My MAX232 TTL to RS232 also works well too.
SEPARATELY!

BUT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

When I connect my CID decoder + RS232 translator to same power supply (that
I designed my self too) every thing goes fine (Please note that still I did
not connect these to boards together just same power supply) BUT as soon as
I connect my SERIAL PORT CABLE to my PC, caller ID decoder circuit STOPS
WORKING!!!!

Please HELP ME!

Thanks in advance.
MAMAD

--
View this message in context: www.nabble.com/What-is-wrong-with-PC-serial-port--tf4505124.html#a12848397
Sent from the PIC - [PIC] mailing list archive at Nabble.com.

2007\09\23@141941 by Gerhard Fiedler

picon face
mamad876 wrote:

> When I connect my CID decoder + RS232 translator to same power supply (that
> I designed my self too) every thing goes fine (Please note that still I did
> not connect these to boards together just same power supply) BUT as soon as
> I connect my SERIAL PORT CABLE to my PC, caller ID decoder circuit STOPS
> WORKING!!!!

As some asked you before -- did you isolate your circuit from the telephone
line? If not, there may be a ground difference between your circuit and the
PC. PC supplies often are not isolated.

Gerhard

2007\09\25@002626 by mamad876

picon face

Hi Gerhard,

Thank you very much for replay.

I read some articles about isolating telephone lines with transformers but I
have a question IS THERE ANY POSSIBILITY TO ISOLATE PHONE LINE WITH
SOMETHING LIKE OPTOISOLATORS?

Thanks,
MAMAD


Gerhard Fiedler wrote:
{Quote hidden}

> --

2007\09\25@072646 by Gerhard Fiedler

picon face
mamad876 wrote:

> I read some articles about isolating telephone lines with transformers
> but I have a question IS THERE ANY POSSIBILITY TO ISOLATE PHONE LINE
> WITH SOMETHING LIKE OPTOISOLATORS?

Depends, but in a sense, yes. You can put your DTMF circuit on the phone
line potential (that is, as you have it now), isolate the digital
connection of it with optoisolators, and put the RS232 interface circuit on
the PC potential. Depending on the needs for the serial link, you may not
even need an isolated power supply for that. There are many circuits
published on the web for this purpose; I just don't have any links handy.

This is a common technique; you have the circuit itself on target potential
and isolate the communication interface to other devices.

Gerhard

2007\09\25@122827 by William Benson

picon face

HI,

Here are couple of link that might be help you.

www.circuitcellar.com/library/print/0703/Wotiz-156/3.htm

www.infomatek.com/Telephone_transmission%20characteristics.htm#interference

www.tkk.fi/Misc/Electronics/circuits/teleinterface.html

www.tkk.fi/Misc/Electronics/circuits/telephone_ringer.html

BEN

> To: spam_OUTpiclistTakeThisOuTspammit.edu> From: .....listsKILLspamspam@spam@connectionbrazil.com> Subject: Re: [PIC] What is wrong with PC serial port?> Date: Tue, 25 Sep 2007 08:25:17 -0300> > mamad876 wrote:> > > I read some articles about isolating telephone lines with transformers> > but I have a question IS THERE ANY POSSIBILITY TO ISOLATE PHONE LINE> > WITH SOMETHING LIKE OPTOISOLATORS?> > Depends, but in a sense, yes. You can put your DTMF circuit on the phone> line potential (that is, as you have it now), isolate the digital> connection of it with optoisolators, and put the RS232 interface circuit on> the PC potential. Depending on the needs for the serial link, you may not> even need an isolated power supply for that. There are many circuits> published on the web for this purpose; I just don't have any links handy. > > This is a common technique; you have the circuit itself on target potential> and isolate the communication interface to other devices.> > Gerhard> >

2007\09\25@125008 by David VanHorn

picon face
> I read some articles about isolating telephone lines with transformers but I
> have a question IS THERE ANY POSSIBILITY TO ISOLATE PHONE LINE WITH
> SOMETHING LIKE OPTOISOLATORS?
>

Yes, I've done it for audio in both directions, but it's not easy.
You'll find transformers for isolaitng the audio to be much easier.

2007\09\25@140417 by mamad876

picon face

Hi again and thank you,

To find a isolating transformer I have opened three modems and two
telephones !!! but I could not find any 1:1 transformer in them.

Actually in modems (two external and one internal) there is just two or four
SMD coils instead of any transformer. a few MOVs, zeners, capacitors and
resistors.

Does any one know how these circuits do the isolation?

Best regards,
MAMAD
--
View this message in context: www.nabble.com/What-is-wrong-with-PC-serial-port--tf4505124.html#a12885063
Sent from the PIC - [PIC] mailing list archive at Nabble.com.

2007\09\25@154658 by William Benson

picon face

Hi,

If you look for directional try this link

www.edn.com/archives/1995/122195/26di1.htm

If you looking for Bidirectional  try this link

www.edn.com/article/CA484493.html?spacedesc=designideas&industryid=44217&q=Phone+wire%2C+RJ%2D11+jacks+and+optocouplers+build+a+bus

BEN> To: piclistspamKILLspammit.edu> From: .....listsKILLspamspam.....connectionbrazil.com> Subject: Re: [PIC] What is wrong with PC serial port?> Date: Tue, 25 Sep 2007 08:25:17 -0300> > mamad876 wrote:> > > I read some articles about isolating telephone lines with transformers> > but I have a question IS THERE ANY POSSIBILITY TO ISOLATE PHONE LINE> > WITH SOMETHING LIKE OPTOISOLATORS?> > Depends, but in a sense, yes. You can put your DTMF circuit on the phone> line potential (that is, as you have it now), isolate the digital> connection of it with optoisolators, and put the RS232 interface circuit on> the PC potential. Depending on the needs for the serial link, you may not> even need an isolated power supply for that. There are many circuits> published on the web for this purpose; I just don't have any links handy. > > This is a common technique; you have the circuit itself on target potential> and isolate the communication interface to other devices.> > Gerhard> >

2007\09\25@154659 by William Benson

picon face

Hi,

If you look for directional try this link

www.edn.com/archives/1995/122195/26di1.htm

If you looking for Bidirectional  try this link

www.edn.com/article/CA484493.html?spacedesc=designideas&industryid=44217&q=Phone+wire%2C+RJ%2D11+jacks+and+optocouplers+build+a+bus

BEN> To: EraseMEpiclistspam_OUTspamTakeThisOuTmit.edu> From: listsspamspam_OUTconnectionbrazil.com> Subject: Re: [PIC] What is wrong with PC serial port?> Date: Tue, 25 Sep 2007 08:25:17 -0300> > mamad876 wrote:> > > I read some articles about isolating telephone lines with transformers> > but I have a question IS THERE ANY POSSIBILITY TO ISOLATE PHONE LINE> > WITH SOMETHING LIKE OPTOISOLATORS?> > Depends, but in a sense, yes. You can put your DTMF circuit on the phone> line potential (that is, as you have it now), isolate the digital> connection of it with optoisolators, and put the RS232 interface circuit on> the PC potential. Depending on the needs for the serial link, you may not> even need an isolated power supply for that. There are many circuits> published on the web for this purpose; I just don't have any links handy. > > This is a common technique; you have the circuit itself on target potential> and isolate the communication interface to other devices.> > Gerhard> >

2007\09\25@155022 by William Benson

picon face

Hi,

No, but I connacted a vendor on line ask for sample and they sent a couple to me.

BEN> Date: Tue, 25 Sep 2007 11:00:12 -0700> From: @spam@mamadharabKILLspamspamgmail.com> To: KILLspampiclistKILLspamspammit.edu> Subject: Re: [PIC] What is wrong with PC serial port?> > > Hi again and thank you,> > To find a isolating transformer I have opened three modems and two> telephones !!! but I could not find any 1:1 transformer in them. > > Actually in modems (two external and one internal) there is just two or four> SMD coils instead of any transformer. a few MOVs, zeners, capacitors and> resistors. > > Does any one know how these circuits do the isolation?> > Best regards,> MAMAD> -- > View this message in context: http://www.nabble.com/What-is-wrong-with-PC-serial-port--tf4505124.html#a12885063> Sent from the PIC - [PIC] mailing list archive at Nabble.com.> >

2007\09\25@175422 by Herbert Graf

flavicon
face
On Tue, 2007-09-25 at 11:00 -0700, mamad876 wrote:
> Hi again and thank you,
>
> To find a isolating transformer I have opened three modems and two
> telephones !!! but I could not find any 1:1 transformer in them.
>
> Actually in modems (two external and one internal) there is just two or four
> SMD coils instead of any transformer. a few MOVs, zeners, capacitors and
> resistors.
>
> Does any one know how these circuits do the isolation?

Transformers I'd guess. The latest ones I've seen didn't have anything
that LOOKED like transformers, they just look like big ICs. TTYL

2007\09\25@211832 by David VanHorn

picon face
> If you looking for Bidirectional  try this link
>
> http://www.edn.com/article/CA484493.html?spacedesc=designideas&industryid=44217&q=Phone+wire%2C+RJ%2D11+jacks+and+optocouplers+build+a+bus


That's not going to help you with telephone stuff.

2007\09\26@121008 by William Benson

picon face

Hi,

I got a free sample (P/N MET-46) of a isolation phone line transfarmer from Tamura Corporation of America Phone (951) 699-1270 http://www.tamuracorp.com.

I hope this helps.

BEN
> Date: Tue, 25 Sep 2007 11:00:12 -0700> From: RemoveMEmamadharabTakeThisOuTspamgmail.com> To: spamBeGonepiclistspamBeGonespammit.edu> Subject: Re: [PIC] What is wrong with PC serial port?> > > Hi again and thank you,> > To find a isolating transformer I have opened three modems and two> telephones !!! but I could not find any 1:1 transformer in them. > > Actually in modems (two external and one internal) there is just two or four> SMD coils instead of any transformer. a few MOVs, zeners, capacitors and> resistors. > > Does any one know how these circuits do the isolation?> > Best regards,> MAMAD> -- > View this message in context: http://www.nabble.com/What-is-wrong-with-PC-serial-port--tf4505124.html#a12885063> Sent from the PIC - [PIC] mailing list archive at Nabble.com.> >

2007\09\26@121207 by William Benson

picon face

Hi,

The article (Phone wire, RJ-11 jacks and optocouplers build a bus --http://www.edn.com/article/CA484493.html?spacedesc=designideas&industryid=44217&q=Phone+wire%2C+RJ%2D11+jacks+and+optocouplers+build+a+bus) show a design for a RS-232 circuit using two optisolators which isolates in both direction.  


The article (Circuit widens optocoupler’s response to 1 MHz  --http://www.edn.com/archives/1995/122195/26di1.htm) show how to design a optisolators in one direction which can be used to isolate his two circuits.  The band width need to be turn back but the is simple modification.

I hope this answer your question?

BEN> Date: Tue, 25 Sep 2007 11:00:12 -0700> From: TakeThisOuTmamadharabEraseMEspamspam_OUTgmail.com> To: RemoveMEpiclistspamTakeThisOuTmit.edu> Subject: Re: [PIC] What is wrong with PC serial port?> > > Hi again and thank you,> > To find a isolating transformer I have opened three modems and two> telephones !!! but I could not find any 1:1 transformer in them. > > Actually in modems (two external and one internal) there is just two or four> SMD coils instead of any transformer. a few MOVs, zeners, capacitors and> resistors. > > Does any one know how these circuits do the isolation?> > Best regards,> MAMAD> -- > View this message in context: http://www.nabble.com/What-is-wrong-with-PC-serial-port--tf4505124.html#a12885063> Sent from the PIC - [PIC] mailing list archive at Nabble.com.> >

More... (looser matching)
- Last day of these posts
- In 2007 , 2008 only
- Today
- New search...