I did consider a PIC on one end, and a RS232 link to monitor temperature,
but what about when the power goes?
I'd (ideally) need to build in some sort of battery backup, and with the
wide variations of temperatures (just below freezing in the winter, all the
way up to 60/70degC in the summer), a battery isn't a really good choice
IMO.
Not only that, if I didn't get a response from the remote PIC, it could be
due to a dodgy cable, wiring fault, the PIC might've hung, etc etc.
Of course, I have 8 pairs, no reason why I couldn't use one as a simple AC
monitoring system using a wallwart, and another one connected to a PIC for
serial comms.

Some questions:
1) Could I use an RS232 link at say 300 baud over such a link - is there
anything I would need to take into account? Can I seriously just connect
each end of the pair to the TX and RX pins on two PICs, or would using say a
MAX232 as well help?
2) I'm not alltogether keen on putting a wallwart plus resistor straight to
the cable for the simple AC monitoring, I'd prefer to have something
definitely limiting the current (yes I know this is what a resistor does),
but considering measuring the resistance of the cable is a bit impratical,
I'd rather just put a semiconductor that is designed to limit output current
to some value and use that between the AC and the cable.


On 25/10/2007, Jinx <joecolquitt@clear.net.nz> wrote:
>
> > WOW, you guys are really into feature creep!!
>
> Haha. No it's not that so much, but nothing says ka-ching like
> 'features'. Even if it's not a lot of ka-ching, and it doesn't have
> to be, giving the customer the ability to monitor the status of a
> product does give them some comfort and reassurance
>
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