I posted the following a couple of days ago but got no responses. Not
sure whether it got out, or whether people got confused by the
inappropriate subject line.
Anybody got any ideas? I'm about to add more sensors to the bus and want
to make sure I'm doing things right.
> 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
> resister at the far end of the cable, and if so then roughly what value. Its
> 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
> The others sit at about 20C and 30C (yes I know this is hot for the wiring
> I'm new to 1-wire, although I've been using Misterhouse for a year or more
> and looking for some help here. Many thanks.