Hi Guil, On 03/02/2011 09:42 AM, Guil Barros wrote:
> The sensor returns 85/185 at startup if it has not had a chance to do > a complete convert_t by the time you read_t on it. My guess is its > either shorting out somewhere and resetting or not getting enough > juice to handle the convert_t. That's what I thought too. Something to do with high humidity in the air, perhaps? > Are the other sensors ok? Are any of the other ones also outside? All other sensors are (were, actually, for the duration of this event) 100% perfect, i.e. no errors, no 85 degrees C returned. The other sensors are all inside. I actually experienced 85 degrees returned by another sensor (every now and then, not continuously for a period of time like in the case of this outside sensor two nights ago), and it that case it turned out that water had gotten inside the wire (this one was a sensor that was monitoring water temperature in a fish tank. I insulated the wire but didn't do a good job so water got in and caused 85 degrees readouts every now and then. As soon as I took the sensor out of the tank and it got dry the 85 degrees readouts stopped). > I have my outside sensor covered in silicone. Its non-conductive, > waterproof, etc. It will delay temp changes slightly as it has a > higher specific heat capacity than air though, but not by much ;) I > have heard of other people using wax for this also as it is easier to > remove if needed but if you live in Texas it might melt off by itself > if left in the sun in summer. Hhmmm. Interesting. Tips like these is exactly what I am after, so thanks a bunch for that. I like the idea of covering the sensor (or parts of the sensor and the PCB) with silicone. Do you remember what specific product you used (was it a spray, or just one of those tubes you buy at HomeDepot or Lowe's that you apply with a gun)? I also like the idea of using wax. I obviously had not thought about it. I suppose that in that case you melt the wax (like from a candle) in a pot and then dip the PCB into it. Is that they way people would do it? I also found about "conformal coating" while doing some searches last night. Guess that is the official name of what I am after. There are products to do conformal coating, although nothing you can find at your local hardware store, which is why I'd prefer to go with one of the two methods you mentioned. > Hope that helps. It does; thanks a lot for the insight :-) Cheers, Eloy Paris.- > On Tue, Mar 1, 2011 at 11:54 AM, Eloy Paris<[email protected]> wrote: >> Hi list, >> >> Apologies for the slightly off-topic message but I figured someone here >> may have some suggestions for me on this non-owfs issue I am having... >> >> I have a DS18B20 sensor located outside. It is in a location that is >> safe from water (unless it rains horizontally). My bus master reaches >> this sensor through a cat5 bus that has about 10 more sensors. The >> sensor, its pins, and the small PCB the sensor is soldered to, are all >> exposed (to wind and humidity, but not to direct water). Parasitic >> powered, and Vcc pin is floating (not connected to ground). This setup >> has been pretty stable (no 1-wire errors or bad temperature readouts in >> 6 months of operation). >> >> Last night there was heavy rain and thunderstorms in the area and for a >> period of about two hours I was getting the dreaded 85 degrees C from >> this sensor. All other sensors were fine during this time and did not >> report 85 degrees. The problem fixed itself a bit after rain and >> thunderstorms passed. >> >> I think it is humidity what causes the 85 degrees C readout since we've >> had a few warm and humid days/nights recently (but no rain) and I've >> gotten a few 85 degrees C readouts here and there from the same sensor. >> But nothing like last night when I consistently got 85 degrees C >> readouts for about two hours. >> >> Next time this happens I plan on grounding Vcc to see if that helps, but >> I also wanted to ask the list for theories on what could be causing >> these 85 degrees C readouts when it is humid (or when there are >> thunderstorms in the area). >> >> If grounding Vcc does not help I think my next step should be to protect >> from the elements the sensor, its pins, and the small PCB. Any ideas on >> how to accomplish this; is there some coating I can spray on the >> sensor's pins and on the PCB that will protect them from humidity? >> >> Thanks in advance for any suggestions. >> >> Cheers, >> >> Eloy Paris.- ------------------------------------------------------------------------------ Free Software Download: Index, Search & Analyze Logs and other IT data in Real-Time with Splunk. Collect, index and harness all the fast moving IT data generated by your applications, servers and devices whether physical, virtual or in the cloud. Deliver compliance at lower cost and gain new business insights. http://p.sf.net/sfu/splunk-dev2dev _______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
