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Local temperature sensors

This post is part of the Temperature monitoring project.

Last part of the project is the local “home made” temperature sensors. They are build using Jeenodes (introduced here).

Given the few number of components needed, I made the plug that holds the temp sensor directly on a 6-pin male header. The pull-up resistor and the cable going to DS1820 are directly soldered onto the header, and the DS1820 is directly attached at the other end.

The pictures bellow show the header and the Jeenode with the header attached.

1820plug1820plugged

Both DS18S20 and DS18B20 can be used, the software has been tested with the two models.

Difference between the two models is mainly the default measure resolution (not the accuracy). The B model is much simpler to use, providing directly 12 bits, the S model requiring some calculation to widen the default 9 bits.

Wonder why 9 bits was not enough? It is because of the fractional part which is very un-precise at 9 bits (I dislike having “big” 0.5° steps).

The pull-up resistor is a little bit lower that we usually see, this is because the sensor operates here at 3V (it’s within the specs).

There is no configuration capability available: code must be re-compiled (I must admit I’ve been a bit lazy not to implement at least reading channel number on ports; I did not pay as much attention as with other parts of the project for this module).

This is true for the following: channel, sending period, RF12 netGroup & nodeID, the DS1820 model.

The standard Arduino library for OneWire has been used.

There also no attention paid to power consumption: those modules were not intended to be battery operated. May be I’ll investigate that later. Jean-Claude, the Jeenode designer, has considered very accurately the Low Power aspects on Jeenodes, see its site.

To finish, you find bellow the diagram, and here the Arduino Sketche.

centralnodediagram

 

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