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TeensyNet™ – DS18B20 Digital Temperature Sensors

Make sure that ONLY DS18B20 parts are used!!
DS18B20P parts are parasitic only, and DO NOT WORK with the TeensyNet™ 

One type of digital sensor used by the TeensyNet™ is the Maxim DS18B20 1-Wire® Programmable Digital Thermometer to monitor temperature. The DS18B20 has a fairly large temperature range, operates on low voltages, and can be acesssed via the 1-Wire® “mini-lan” over considerable distances. Eash DS18B20 has its own unique 64-bit digital address and a large number can share the same mini-lan with no interference. The response time of the device varies with the precision required, from a high of about 750ms for 12-bit precision to about 125ms for 9-bit precision. The TeensyNet™ eschews high precision for rapid response, so the TeensyNet™’s accuracy is plus or minus 1°C. For a home brewery system, home fermentation chamber for beer or wine, sous vide, etc, this is perfectly acceptable. Higher accuracy can be obtained,at the expense of response time, with software changes to the TeensyNet™ Board and web software.

There are numerous vendors that will sell you pre-made temperature probes utilizing the DS18B20, including Adafruit, Brewers Hardware, Sparkfun, E-bay and others. Just make sure that you get a cable that uses the three wire powered mode for the chip, not the cheaper, slower, less reliable two-wire “parasitic-mode” cables. If you are going to immerse the sensor in liquids, especially hot liquids, I recommend that you get a probe set that uses a stainless steel insert, otherwise plastic is just fine.

The DS18B20 is part of the Maxim 1-Wire® series of parts that are made to communicate over a single wire. The connections are very simple:

 

The 1-Wire® mini-lan works best as a daisy-chain, where the sensors are connected directly to the main cabling or by short stubs of less than 9 feet. The mini-lan can also be setup as a star configuration, where the TeensyNet™’s main cable is connected to a junction box, and the individual cables radiate out from that point. I have tested both configurations, and both seem to work with minimal problems. I have used both the RJ15 and RJ45 connectors on the cabling with great success, but the choice of cable connectors is up to you.