That's why I suggested using the MAX31865. It's an SPI RTD reader. I use it already, but would prefer it on a longer multi drop bus where an IO per chip select is unnecessary. It's 3.3V so either the 1Wire bus is on 3.3V (as well as the micro), or you use an LDO to bring it down to 3.3V for the RTD chip and logic level convert the SPI.
To expand on what you said about probe selection, I only use an RTD where the range of 1Wire temperature probes such as the DS18B20 won't cut it, or when I have temperature controllers that use them out of the box. Accuracy is a wash unless you go out of your way to carefully calibrate. I never use thermistors, and can count the times I needed the range of thermocouples in the <0.1% category. I avoid them at all costs due to the annoying CJC, cabling issues, and signal processing. Colin > On Aug 28, 2015, at 9:14 PM, Jerry Scharf <sch...@lagunawayconsulting.com> > wrote: > > Colin, > > The reason I and most other people use RTDs is because they are more precise > than a typical thermocouple or thermister. You need to do a good bit more > than an LDO and a A/D to make the reader as/more stable than the RTD. > Everything needs to be temperature compensated with careful circuit choices > to get reasonable accuracy. I'm not sure how much better than a typical > thermocouple a setup like you suggested would be. > > jerry > > >> On 08/28/2015 12:47 PM, Colin Reese wrote: >> Hi All, >> >> Anybody have use for an RTD 1Wire slave? I'm finding I could really use one, >> and what's out there is too expensive, not compact and/or modular enough. I >> feel as though I'm missing something. >> >> Seems to me a MAX31865, an ATTiny85, an LDO, and a little logic level >> conversion would do the trick in a tiny form factor for a pittance. What ROM >> address would/could I use for this guy? >> >> Cheers, >> Colin >> >> >> ------------------------------------------------------------------------------ >> >> >> _______________________________________________ >> Owfs-developers mailing list >> Owfs-developers@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/owfs-developers > > ------------------------------------------------------------------------------ > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers
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