Author Topic: Schneider RS232 Interface  (Read 2383 times)

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Offline Carpallo

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Schneider RS232 Interface
« on: 01:20, 02 May 15 »
Hi all!


Some years ago I bought a Schneider RS232 interface like the one you can see in the CPCWiki:


Schneider RS232 Interface - CPCWiki


But the problem is that it came without the power adapter and it is a little bit odd. Its output is 8 VAC 100mA. Somebody knows where can I get one at a reasonable price? I have found one in eBay but it costs 34,98 € shipping included.


Does somebody know of some place where an RS232 interface can be bought?


Thank you all. Best regards

Offline Poliander

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Re: Schneider RS232 Interface
« Reply #1 on: 11:01, 02 May 15 »
Oh, I sold 3 or 4 of those interfaces over the past months on eBay (with original power adapter included). But this one from Conrad offers the right output current. Those power adapters are sold sometimes as "no-name" adapters on eBay. They show up sometimes, I guess they sell customer returns there... I got mine for 20,00 € instead of 45,00 €.
« Last Edit: 11:06, 02 May 15 by Poliander »
Schneider CPC 664 • X-MEM • X-MASS • CTM 644 • DMP 2160 — Schneider CPC 6128 • M4 Board • Z-MEM • OSSC

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #2 on: 23:36, 02 May 15 »
Thank you for your comment, Poliander, but I believe that you misunderstood the output voltage... it supplies 8 Volts AC (Altern Current) not DC (Direct Current). That is why this adapter is quite strange and is so hard to find.

Offline gerald

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Re: Schneider RS232 Interface
« Reply #3 on: 12:26, 03 May 15 »
Thank you for your comment, Poliander, but I believe that you misunderstood the output voltage... it supplies 8 Volts AC (Altern Current) not DC (Direct Current). That is why this adapter is quite strange and is so hard to find.
The 8V AC is just used to power the RS232 line driver with +/- 10.5V. This voltage is also going to the interface port : was there a motherboard to plug them ?
You should be able to use the interface with a any AC power supply between 5V and 9V which gives about +/- 7v to +/- 12v which are the min and typical required voltage for the line driver (MC1488)

It may also work from a single 12V DC voltage.


Offline TCMSLP

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Re: Schneider RS232 Interface
« Reply #4 on: 13:29, 03 May 15 »

A simple PSU could probably be put together by hacking apart an old linear transformer based PSU and removing the rectifier/regulator.

On a related note - does anyone know of terminal emulator software that supports the Schneider interface?

Offline kevin.c

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Re: Schneider RS232 Interface
« Reply #5 on: 18:32, 03 May 15 »
There is another solution I used in my RS232 interface. Some time ago I replaced line drivers 1488 and 1489 with one  ICL232 (or MAX232). This IC has internal voltage converters and does not require additional power supply. My ICL232 with electrolitic capacitors is on little subboard.
Anyway this mod require some basic soldering skills...

Offline TFM

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Re: Schneider RS232 Interface
« Reply #6 on: 04:38, 04 May 15 »
On a related note - does anyone know of terminal emulator software that supports the Schneider interface?

Yes, there is one.... part of Starwriter... IIRC

Star-Writer - CPCWiki
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Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #7 on: 11:56, 04 May 15 »
Thanks a lot for all your comments!


The RS232 interface has been getting dust for some years and I would like to make it work and perhaps connect it to an Arduino board.


Gerald, do you really mean that it should work also with a 12 DC power supply? Instead of AC?


Thanks for your idea about hacking a PSU by removing the rectifier, it's a very good idea. I only have to find an old PSU to be hacked.


Thank you also, Kevin. I had thought about using the MAX232 but it seemed so easy that I thought it couldn`t work. Do you have one RS232 interface working with MAX232? Perhaps I am not a master but I have some soldering skills, so I could try to do it. Do you have some kind of scheme of the mod? I would appreciate it!!!


Thanks a lot again to all!


Best regards

Offline gerald

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Re: Schneider RS232 Interface
« Reply #8 on: 14:35, 04 May 15 »
Gerald, do you really mean that it should work also with a 12 DC power supply? Instead of AC?
Well, it could work with a 12V DC.
I do not have any design with the 1488, but if it is OK, the only difference with the AC power supply is that the RS232 will use 0/+12 signalling instead of -12/+12. Pace RS232 interface is using 0/+5V (but does not use the 1488).
Note that you must connect the 12V power supply GND to the interface GND.

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #9 on: 16:23, 04 May 15 »
Thank you, Gerald! I'll take it into account.

Offline TFM

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Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #11 on: 01:20, 05 May 15 »
Wonderful hack, TFM!


I think I am going to try it with one old 12 V PSU!


Thank you very much to all for your comments! Best regards

Offline kevin.c

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Re: Schneider RS232 Interface
« Reply #12 on: 09:33, 05 May 15 »
Sorry, but I can't agree with you about  12V DC power supply. Line driver 1488  will not work without negative voltage! Look at the the gate schematic.
Application note recommends minimum negative voltage:  Texas Intr. -7,5V  and Motorola -2,5V.
http://www.ti.com/lit/ds/symlink/sn75188.pdf

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #13 on: 11:05, 05 May 15 »
Sure you are right, Kevin!


I am going to take one 12 V PSU and remove the diode brigde in order to obtain AC voltage, as the hack that TFM posted says. This way I can get +/- 12 V AC from the PSU.

Offline Bryce

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Re: Schneider RS232 Interface
« Reply #14 on: 11:44, 05 May 15 »
Make sure it really is only giving you 12VAC before the rectifier. The hack that TFM linked to is specific to a certain type of PSU, other 12VDC PSUs could have anything up to about 20VAC in front of the rectifier.

Bryce.

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #15 on: 13:53, 05 May 15 »
Thank you, Bryce! I will check it up before. Well, I need only 8V AC in fact but...

Offline Bryce

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Re: Schneider RS232 Interface
« Reply #16 on: 15:40, 05 May 15 »
If the PSU uses a regulator such as an LM7812, these have a dropout voltage of 2V, ie: the input voltage needs to be at least 14V to give a properly regulated 12V output. If designed properly, the designer will have added some overhead, so the AC side is probably about 16VAC allowing for the voltage drop across the rectifier diodes gives you 14.8VDC which is then regulated to 12V.
If the PSU has a different voltage regulator on the PCB, check the dropout voltage from its datasheet, then you'll have a rough idea what AC voltage the transformer is producing. Some regulators have much higher dropout voltages!

Roughly speaking (without overhead allowance): AC voltage of transformer = DC rating + dropout voltage of regulator + 1.2

Bryce.

Offline TFM

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Re: Schneider RS232 Interface
« Reply #17 on: 18:51, 05 May 15 »
Yes, it's important to really check if it works. It's just crazy how expensive AC PSU's are! I got a DC (5V, 3A) for less then $3 at amazon-usa (that's crazy cheap too, but works like a charm with all X4 stuff).



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Offline Bryce

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Re: Schneider RS232 Interface
« Reply #18 on: 21:28, 05 May 15 »
AC supplies are rarely needed these days = low volumes = high prices.

Bryce.

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #19 on: 13:46, 06 May 15 »
Do you think that this trafo could do the job?





It costs only 6,60 € + 5,90 € (shipping)!!!

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #20 on: 13:58, 06 May 15 »
According to the specifications of the Schneider RS232 Interface, it only needs 8V AC 100mA... so I presume that with this one it should work.


It supplies 9V AC and 300 mA

Offline Bryce

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Re: Schneider RS232 Interface
« Reply #21 on: 14:44, 06 May 15 »
Yes, that should be fine, but you will have to find a suitable housing and connect / isolate the wires as required. I'd also add a fuse (in holder) on both sides.

Bryce.

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #22 on: 15:39, 06 May 15 »
Thank you Bryce!


As it is altern current I presume I don't have to worry about polarity in the wires, have I?


About the fuses... do you mean to put one of them on each wire?

Offline Bryce

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Re: Schneider RS232 Interface
« Reply #23 on: 17:13, 06 May 15 »
No, you don't need to worry about polarity. The fuses need to be on either side, ie: On the 240V side (input) and the 9V side (output). I would use a 2A on both the input and output. this will save your house wiring if the primary coil shorted and will save your transformer if there's a short on the 9V circuit.

Bryce.

Offline Carpallo

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Re: Schneider RS232 Interface
« Reply #24 on: 17:16, 06 May 15 »
Thank you very much as always, Bryce!