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'[OT]: Help Wanted, UPS Interface'
2000\07\22@083026 by James Cameron

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G'day,

I'm trying to figure out the interface pinout for a uninteruptible
power supply (UPS) that I have.  The unit came with no documentation,
and no interface cable, and I suspect that the cable may require some
pin remapping anyway.

If you are willing to help, I've drafted a schematic of the circuit in
the UPS attached to the DB9.  I've not gone beyond the optocouplers; I
got rapidly lost.  I've also taken a few snapshots of the PCB.

       <http://quozl.netrek.org/p600v/> (220k of images)

The UPS is straight analog; there are no digital components on the
PCB, no crystals, no microcontrollers (sadly), just bog standard
things like LM339's.  I suspect therefore that the signalling from the
UPS to the PC is just "online" and "low battery", via modem status
lines.  But there's a twist; there is an optocoupler facing the other
direction.  I can't figure out what function it has.

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James Cameron    spam_OUTquozlTakeThisOuTspamus.netrek.org     http://quozl.netrek.org/

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2000\07\22@112031 by Ries van Twisk

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Hi,

One of my UPS's is also pritty simple. I don't know te exact meaning of the signal lines but it's RS232 'compatible'. This means you can connect it to the PC using standard RS232 interface.

Wy don't you monitor the status lines of the UPS or connect the status lines to some leds. Just load the UPS and see when the UPS goes offline and what happens to the status lines (low power etc).

Check out the Linux docs the also have some really good docs about UPS, I think there is a 'standard' for it.

Also check out the brand and just call them for the docs.

Ries

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2000\07\22@114307 by John C. Frenzel

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James,
I faced the same problem with a surplus UPS I got.  Take a look at the Linux
UPS Howto on metalab.unc.edu/mdw/HOWTO/UPS-HOWTO.html . They have a section
on different interface types.  Although my UPS was not listed, given a
little testing and looking at the different diagrams, I was able to come up
with what it was doing pretty quickly.  The HOWTO also has a section on
cable building and of course how to get it working under linux.
John
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2000\07\22@120219 by Ricardo Seixas

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James,

There's an UPS howto on the linux docs,  there's a lot of info on pinouts,
maybe it can help.


>G'day,
>
>I'm trying to figure out the interface pinout for a uninteruptible
>power supply (UPS) that I have.  The unit came with no documentation,
>and no interface cable, and I suspect that the cable may require some
>pin remapping anyway.




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Ricardo Seixas
.....rseixasKILLspamspam@spam@pobox.com
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2000\07\22@121919 by Oliver Broad

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The one in the other direction is probably remote shutdown. Where a UPS is
used unattended it is common to have software to force a controlled shutdown
after a time limit to protect the battery.


{Original Message removed}

2000\07\23@215121 by Robert Francisco

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By the way- RS232 signals swing between positive(3~11volts)  and
negative(3~11 volts)  for it's logic states.


{Original Message removed}

2000\07\24@090528 by smerchock, Steve

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James,

The unknown could be a way for the PC to tell the
UPS to "shutdown". Just a guess!!

Steve

{Original Message removed}

2000\07\24@095401 by Michael Rigby-Jones

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> -----Original Message-----
> From: Oliver Broad [SMTP:obroadspamKILLspamTELINCO.CO.UK]
> Sent: Saturday, July 22, 2000 5:19 PM
> To:   .....PICLISTKILLspamspam.....MITVMA.MIT.EDU
> Subject:      Re: [OT]: Help Wanted, UPS Interface
>
> The one in the other direction is probably remote shutdown. Where a UPS is
> used unattended it is common to have software to force a controlled
> shutdown
> after a time limit to protect the battery.
>
>
That would make sense.  There is an RC filter on the input with a very high
time constant.  Presumably to avoid any interference that could appear on
the RS232 line from immediately shutting down the UPS.

What is a little suspicious is that there is nothing to prevent the
electroylitic cap having a reverse polarity applied from the RS232 lines,
although there is a diode which must be there to either stop BE breakdown of
the transistor and/or to increase the effective delay time of the 890K/47uF
combination.

Regards

       Mike



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2000\07\24@174437 by Peter L. Peres

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The standard controls for a dunb UPS are:

power fail:   active low   ups -> computer
battery fail: active low   ups -> computer
shutdown:     active high  computer -> ups

The shutdown command hopefully works only when the UPS is running on
battery otherwise you will (may) have serious setup problems with a
straight cable (peripheral probing during boot can shutdown). Check with a
desk lamp and a PSU (or 4.5V battery + 1k resistor).

You can check the PSU outputs with a DVM set for diode range.

Then make a cable (you may also refer to the Linux UPS-Howto which is way
out of date imho but contains useful clues and doubtful circuits - beware
!).

Peter

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