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'[PIC] Problem With MAX232'
2007\09\15@011522 by mamad876

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Hi all,

Recently I made a Caller ID decoder using SM8223 chip and I decided to
connect it's out put to computer serial port and I bought a MAX232 chip and
I made a prototype board regarding to it's data sheet.
My problem is when I use my decoder separately it works well (I think
because actually I don't see the result but I can see the CID found signal
with an LED connected to board) but just when I connect ANY PINS of my RS232
converter to the CID board (Even GND wire of my RS232 Pro board) it stops
working (ie. LED doesn't show CID signal ). I tried to separate the Power
supply of my boards but this time the same problem when connecting TxD (ie
T1 pin) of MAX232 to CID decoder serial output was exists.

NOTE:
I tested my RS232 board with another board with PIC16f84 and it works fine!

Does any one have a suggestion.

Thanks in advance.
MAMAD
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2007\09\15@044549 by Vasile Surducan

face picon face
SM8223 appears it need +3V. So you need an RS232 transciever which run at 3V.
http://www.npcamerica.com/pdf/SM8223.pdf

On 9/14/07, mamad876 <spam_OUTmamadharabTakeThisOuTspamgmail.com> wrote:
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2007\09\15@055819 by RICH

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I assume both boards operate on the same voltage?

----- Original Message -----
From: "Vasile Surducan" <.....piclist9KILLspamspam@spam@gmail.com>
To: "Microcontroller discussion list - Public." <piclistspamKILLspammit.edu>
Sent: Saturday, September 15, 2007 4:45 AM
Subject: Re: [PIC] Problem With MAX232


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2007\09\15@071932 by RICH

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There are a variety of things that could be wrong.  Grounding is one, power
is another.  Could you try another RS232 device with the board that fails?
{Original Message removed}

2007\09\15@082239 by David VanHorn

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Are you properly isolating your circuit from the telephone line?

2007\09\15@082409 by enkitec

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       Are you using a transformer between your decoder and the phone line?

       


On 14 Sep 2007 at 22:15, mamad876 wrote:

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2007\09\15@092943 by Carl Denk

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face
After you get it working, I would be interested in the setup. My
application is a PLC with RS-485 (could be converted to RS-232)
controlling a standby generator, that I would like to call out with
speech synthesis (still looking for a way to do this) to a list of
numbers, until it found a person answering that would acknowledge with a
key press that thet had control of the situation. Message would be a
power, generator, or pump failure status sort of thing that needed human
attention that the PLC would ut out on the serial connection as ASCII text.

mamad876 wrote:
{Quote hidden}

2007\09\15@120622 by mamad876

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Is it important? It uses two capacitors as AC filter and then a diode bridge
also to stabilize the signals.

Actually I'm very new to electronics.
If you think the problem is isolation from telephone line would you please
explain me why?

Thanks for your attention.


enkitec wrote:
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> --

2007\09\15@120819 by mamad876

picon face

Is it important? It uses two capacitors as AC filter and then a diode bridge
also to stabilize the signals.

Actually I'm very new to electronics.
If you think the problem is isolation from telephone line would you please
explain me why?

Thanks for your attention.


enkitec wrote:
{Quote hidden}

> --

2007\09\15@121308 by mamad876

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Hi,

Yes you are right,

And I'm running my decoder with two AA batteries and RS232 translator with
separated 5.0 V power supply. Please see below.


Vasile Surducan-2 wrote:
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2007\09\15@140820 by David VanHorn

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> Is it important? It uses two capacitors as AC filter and then a diode bridge
> also to stabilize the signals.
>
> Actually I'm very new to electronics.
> If you think the problem is isolation from telephone line would you please
> explain me why?

I highly recommend that you get a copy of the book "understanding
telephone electronics".

Properly designed isolation from the phone line is critical to
anything like this working properly, and also not disturbing the telco
network, or endangering phone technicians.

2007\09\15@144457 by mamad876

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Ok,

But I could not find this book in my country and also I can not order
online.
Do you know any online resource about telephone communication circuits?

Thank you.


David VanHorn-2 wrote:
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2007\09\15@174431 by enkitec

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On 15 Sep 2007 at 11:44, mamad876 wrote:

> Do you know any online resource about telephone communication circuits?


       Google.com

2007\09\15@183255 by Jinx

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> speech synthesis (still looking for a way to do this)

ISD is probably the simplest solution

http://www.winbond.com/hq/enu/ProductAndSales/Solutions/ISDVoiceICSolution/

2007\09\15@185202 by Carl Denk

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face
Thanks for the tip, I have saved their home page, but looks like they
need to do the programming of the message. I am hoping to go from Ascii
text the telephone line, or at least where I can change the messages as
time goes on.  :)

Jinx wrote:
>> speech synthesis (still looking for a way to do this)
>>    
>
> ISD is probably the simplest solution
>
> http://www.winbond.com/hq/enu/ProductAndSales/Solutions/ISDVoiceICSolution/
>
>  

2007\09\15@192919 by David VanHorn

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On 9/15/07, mamad876 <EraseMEmamadharabspam_OUTspamTakeThisOuTgmail.com> wrote:
>
> Ok,
>
> But I could not find this book in my country and also I can not order
> online.
> Do you know any online resource about telephone communication circuits?

Ouch..  No, I really am not aware of anything online that will show
you what you need to know.  This book has designs and information in
it that you won't find elsewhere, as well as a very thorough, and yet
concise description of how analog phone lines work, and what you need
to do to interface to them.

I don't have an extra copy either, or I'd loan or sell you one.

Searching it on amazon.com returns several links.
http://www.amazon.com/understanding-telephone-electronics-Radio-Shack/dp/B000IXKVPI/ref=sr_1_5/105-8054198-8716424?ie=UTF8&s=books&qid=1189898760&sr=8-5

The one I have, and recommend, is the red one from radio shack.
The later one is thicker, and more expensive, but in my opinion the
red one is everything that you need.

You CAN do this, and you CAN do it well, but you need to understand
the basics of interfacing to the line.   Note, this book describes US
telephone systems. Other countries phone lines are generally similar,
but differ in details like impedance, and the voltage and current
levels.

2007\09\15@204437 by William Benson

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2007\09\16@005059 by mamad876

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Thanks to all of you,

I need some time to do your suggestions and I hope I can solve this problem.
I'll come back later whether it works or not.

Best regards,
:-/
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2007\09\17@144551 by William Benson

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European phones work on 900 ohm Z, I believe, and I do not know the dbm level (0 to -8 dbm for voice; -8 to -16 dbm for Data USA) but if you chech out this URL (which a Eurpean remote temperature controller) http://www.apogeekits.com/PDF_Files/Manual_K6502.pdf; you will see how they interface the phone lines with UM9270/MT8870 which should have the same input as MAX232 and then to the PIC chip.  I do not know what you trying to so I can not really help you but there is a world of circuit out there internet.  Note: even in the States the different type (voice, Data, Voice over Data) of lines have different Level dbm levels of opetions.

Try this URL http://www.nexicom.net/~loscann/files/picproject.html for some one that has built an interface with computer/PIC board/phone lines.

I hope this helps.
 > Date: Sat, 15 Sep 2007 19:29:14 -0400> From: RemoveMEmicrobrixTakeThisOuTspamgmail.com> To: spamBeGonepiclistspamBeGonespammit.edu> Subject: Re: [PIC] Problem With MAX232> > On 9/15/07, mamad876 <TakeThisOuTmamadharabEraseMEspamspam_OUTgmail.com> wrote:> >> > Ok,> >> > But I could not find this book in my country and also I can not order> > online.> > Do you know any online resource about telephone communication circuits?> > Ouch.. No, I really am not aware of anything online that will show> you what you need to know. This book has designs and information in> it that you won't find elsewhere, as well as a very thorough, and yet> concise description of how analog phone lines work, and what you need> to do to interface to them.> > I don't have an extra copy either, or I'd loan or sell you one.> > Searching it on amazon.com returns several links.> http://www.amazon.com/understanding-telephone-electronics-Radio-Shack/dp/B000IXKVPI/ref=sr_1_5/105-8054198-8716424?ie=UTF8&s=books&qid=1189898760&sr=8-5> > The one I have, and recommend, is the red one from radio shack.> The later one is thicker, and more expensive, but in my opinion the> red one is everything that you need.> > You CAN do this, and you CAN do it well, but you need to understand> the basics of interfacing to the line. Note, this book describes US> telephone systems. Other countries phone lines are generally similar,> but differ in details like impedance, and the voltage and current> levels.>

2007\09\17@160718 by David VanHorn

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On 9/17/07, William Benson <RemoveMEben1son1spamTakeThisOuThotmail.com> wrote:
>
> European phones work on 900 ohm Z, I believe, and I do not know the dbm level (0 to -8 dbm for voice; -8 to -16 dbm for Data USA) but if you chech out this URL (which a Eurpean remote temperature controller)

I have seen 600, 900, and several versions that were 600/900 plus a
significant reactive component, and return loss requirements
(impedance matching) up to 18dB, plus very high level tone bursts that
had to be dealt with.

Normally, in the US, -9dBm is max level for transmit.

2007\09\17@195237 by William Benson

picon face

The USA system is 0dbm to -8dbm in and -8 dbm to -16dbm out for voice and -8dbm to -16dbm in and -16dbm out for data.  It been about 15 years since I work on telephone line.   Line amp are set cut for an signal over 0 dbm.

BEN

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