Re: [misterhouse-users] Including an image

[Nigel T. <ni...@pa...>]

Folks,

Just added 1-wire functionality to my Misterhouse setup. At the moment
this consists of three DS18S20 temperature probes on about 30m of 
telephone cable, with a DS9097U-S09 serial converter on the Misterhouse box. 
One probe is at the far end and measures the temperature 
in our annex, the middle one, about 8m from the live end measures outside
temps and the close one, about 1m from the live end is in the wiring closet.
It all works fine, except that the middle one fails to complete a temperature
measurement about 10% of the time. I've extended the timeout in the iButton
interface package to 750mS, which is what the DS18S20 documentation says is
the maximum measurement interval, and I still get a return value of 85C, which
indicates that the measurement is not completing, about 10% of the time.

Anybody got any ideas about what could be causing this. Do I need a terminating
resister at the far end of the cable, and if so then roughly what value. Its odd
that only the middle one is returning bad results, unless its related to the
fact that its average temperature is lower (about 5 - 10C at this time of year).
The others sit at about 20C and 30C (yes I know this is hot for the wiring closet...)

I'm new to 1-wire, although I've been using Misterhouse for a year or more now, 
and looking for some help here. Many thanks.

Nigel
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