Re: Sensing stuff

[Nigel Orr <nigel.orr@xxxxxxx>]

At 17:25 30/03/00 +0100, you wrote:
>    5) Low water in my hamster Bob's bottle.

Not sure that should be part of the prototype system- maybe when it's
stable (though I admit to having an automatic feeder designed to be
triggered by Comfort, to feed our rat if we're away for a day... it's
slightly less critical as she's usually hoarded some anyway, and it's only
a one-off...)

>want to do is create a door entry system with the iButtons. Being me I
think
>that this is just as secure as having a key, in fact maybe more so,
because
>keys can be copied, iButtons cannot.

The ID ones can be, quite easily (ie I could build a circuit with a reader
on one side, an ibutton shape on the other, 1 switch, and a PIC
microcontroller, which would duplicate an ID button).  The crypto ones are
much more secure.  Even for the ID ones, it still needs the person to have
your button to copy it, which is probably as likely as stealing your key.

Of course, you will then have an electrically releasable door, so the
reliability of the whole system has to be as good as a standard lock.  I
have to say I quite like the idea of central locking for the house- secure
keyfob or iButton to control it all.

One other thing you could do is to have a 'spare key' under the mat or
wherever, which is only active for, say, 1 minute in a 1 hour period, and
only when no-one is at home, and only at the sort of time you would expect
to come home anyway.  That's a lot more secure than a standard key.  If you
can disarm your alarm remotely, like Comfort, you could even have it only
recognise the spare key for 5 minutes after the alarm is disarmed.

>However, the missus doesn't agree, and thinks it's just going to leave
the
>door open to every Tom Dick and Harry, complete with flashing "Rob
Me" sign.

It's about as secure as a key.  Assuming the release bit is too.  But the
crypto ones would be a sensible step.

Nigel


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