On Thu, 9 Sep 2004, Martin McCormick wrote:

> "Ruben_J=F6nsson?=" writes:
>> though). The trick here is for the master to keep the line low not too short
>> and not too long, which depends on the RC time for the line which in turn
>> depends on the length and the number of devices on the bus.
>
> 	Thanks for all that information.  You have already saved me
> from one bad design.  I had this image of stringing telephone wire all
> over the house and placing sensors here and there to read
> temperatures.  I am sure this can be done, but I think each sensor
> will need a buffer or maybe even a PIC to
> interface between the DS18S20 and the long wire.  It might even be a
> good application for some sort of wireless technique instead of
> stringing wire.  In that case, each sensor would definitely need a PIC
> to handle the data and communication.  A 12F675/29 or even a 12C508
> could probably do that very nicely.

Unrelated, but you might want to know that there is a profusion of Chinese 
weather 'computers' on the market, using wireless 433MHz external sensors. 
These could be used as is, or dyi using a temperature sensor, a PIC coder 
and a 433 MHz tx at each location (including outside), using some form of 
time spread transmission (aloha etc).

Peter
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