Re: Re: Non-Comfort Alarms

[James Derrick <james@xxxxxxx>]

On Thu, 12 Jul 2001 00:09:02 +0100, you wrote:

>	I'll have a shot as i'm just waiting for a download to
>complete - Newcastle accents take a bit of getting used to -

Whey ya bugga man, whit ya gannin oon aboot, like?

Ahem. ;-)

Thanks Kevin, your explanation of my binary was correct! Alarm panels
tend to use 12v, whereas PC inputs tend to use 5v. The chip
'level-shifted' one set of voltages t  the other.

The disadvantage of this approach is that 8 zones needed 8 wires plus
2 for power t  lead from the alarm t  an input board in the PC. A
better solution, as Kevin says is to use a serial interface t  talk t
an intelligent alarm, such as Comfort.

Many newer alarms use remote keypanels with buttons and LED status
indicators. To save wires, these use a serial interface, however it
usually uses some arcane language known only t  the manufacturer, wh
is not going t  tell you in case you use the information to disable
other alarms!

It would be possible but time consuming t  reverse-engineer the signal
and add a PC interface. Apart from the satisfaction gained, it is
probably cheaper t  find a specialist alarm with a serial interface
designed for monitoring.

Another approach is t  get a PC digital i/o board with inputs and
outputs and write an alarm system in software. Even an old 486 would
do- my first HA system was a 386-16 with a bit of MSDOS basic running
from a floppy disk. Hell, with visual basic for applications, you
could even write the thing using MS Access!

You don't need a PC as there are many small single-board controllers
out there now which could do the lot. Look at Parallax BASIC Stamps-
these are a wh le micro controller on a board which is programmed in
BASIC.
http://www.milinst.com/stamps.htm

Just a different approach...

James





James Derrick    james@xxxxxxx, Cramlington, Near Newcastle, England
Beyond the Horizon of the place we lived when we were young,
In a World of Magnets and Miracles. Pink Floyd.



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