Re: Temperature Sensing.

[Nigel Orr <nigel.orr@xxxxxxx>]

At 18:06 10/01/00 -0000, you wrote:
>path (2 wires) and IIRC to use a lot of temperature sensors you real
need 3
>wires as the parasitic power drain is quite high for the temperature
sensors
>( I could be wrong on this).

The power supply can be supplied locally, rather than from a central point-
the bus (a bit like the outputs in comfort!) was sensibly designed to
pull-down rather than pullup, so you can add separate power supplies to the
sensors with little effort...

I don't have the figures to hand for the temp sensors, but if there's only
a few they might not need extra supplies.  The switch/input chips are a bit
more greedy, and the ID chips are the least current-grabbing...

BTW, if you fancy some delicate soldering, Dallas are giving away samples
of the ID chips at http://www.ibutton.com/csp.html
.  I got mine before
Christmas, but I haven't had time to play yet!  They are _awfully_ small
though, so unless you are used to hot-air soldering, it's probably not
worth your while except as something (very small) to put on the wall...

Nigel


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