Hi patyrk, On 03/02/2011 05:09 AM, patyrk wrote:
> Dnia 2011-03-01, wto o godzinie 12:54 -0500, Eloy Paris pisze: > >> 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? > > I soldered some wire(20cm) directly to DS18b20 pins with VCC and GND > together and put it in a heatshrink tube and placed the connector to the > rest of the network inside. Good suggestion. I built a cable like that for monitoring water temperature in a fish tank. The sensor was actually submerged. It got wet because of bad final insulation (silicone not being tight) but I plan to try again. As I mentioned in my previous message to Paul, I think I will re-purpose this cable I am (was) using for the fish tank and use it outside instead. > Maxim suggests connecting Vcc do GND when using parasite power. Maybe > you have DS18B20+PAR with Vcc and GND already connected internally. Yup, I am aware of the recommendation. My current 12 sensors do not have Vcc grounded and they have been working fine so far, though. They are regular 18B20s, not the -PAR version. Related to this practice of not grounding Vcc when using parasitic power, I found this in the manual for iButtonLink's T-Sense sensor (http://www.ibuttonlink.com/pdf/manuals%20for%20t-sense%2005-22-08.pdf): "NOTE: Important information There is a small chance that the bus could become unstable when using T-Sense units as the only sensor on the bus. This condition comes about as a result of the new design of the T-Sense, using the DS18B20 sensor. The third lead on the DS18B20, (Vdd) is left floating, (to allow design flexibility for sophisticated networks) which leaves the possibility of unpredictable performance. Our engineering department has not been able to create this condition. Experiments with > 30 T-Sensors on the bus, and a variety of interfaces, have shown all devices working properly. In the unlikely event of unstable behavior on the bus, resolution can be accomplished by simply connecting pin 2 (+5 volts) to pin 6 (Aux). Alternately, any MS-xx product on the bus will provide the jumper internally, or the use of a LinkHub as the interface." 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
