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100 Node Micro-lan (DS18B20 Sensor Network)

By Dale Reagan | June 26, 2011

Well, maybe not 100 nodes in ‘production’ but 100 nodes during testing…

I started out on a simple data quest that evolved into a detailed data quest.  The original question:

How hot is the attic? (Update – 2011 Data at: cooler-house.georgia-usa.com/)

Living in the sunny south attic temperatures can dramatically impact overall heating/cooling costs and conditions – some initial questions included:

Going back to the questions, “How hot is the attic?”

It’s not a simple question/answer set unless you have a simple attic/roof.  We have a complex, ‘hip roof’ with:

While it would be simple to just use 3-5 sensors and then average the temperature data, I have decided to extends things a bit – the sensor network will need to provide data for each section of the attic space – I should be able to ‘watch’ the temperature changes as the sun passes overhead.  Since I do have time (or at least I am willing to wait) and since I don’t have big bucks for a modern computing simulation approach I will simply collect and review real data.   As I try out vendor products I should have a reasonable assessment for my installation/implementation of whatever the product might be (i.e. significant impact, no measurable difference, small impact, etc.)

Back to the ‘Micro Lan’ – the DS1820 is a temperature sensor from Maxim-IC – it has some unique properties including:

Finding/discovering the best ‘network solution’ is challenging.  The Maxim web site provides many guiding documents but I did not locate any external, real, ‘in the field’ data/test/illustrations. Via search engines I did find quite a number of less than ~20 sensor node discussions/projects.  For this project I will most likely document yet-another-custom solution – but using a larger network of devices.

I start by building an 18 node MicroLan using the 1wire networking solution.  The DS18B20 sensor is available in a TO-92 ‘chip package’ (also known as a ‘chip container’ or ‘chip carrier’) so there are three pins on each sensor.  For this projects the middle pin is connected to ‘power’ while the other two pins connect to ‘ground’ (when using parasite power.)  You can place the devices in parallel on your network; at some point you will encounter ‘problems’ when the ‘weight’ of your network is too ‘heavy’ for the desired network response from your nodes.  Why 18 nodes?  Simple, that’s what easily ‘fits’ on my initial breadboard….

The wiring for the DS18B20 is simple:

Arduino Uno - 1-wire Micro-Lan - DS18B20.

The photo above – a 4 node DS18B20 Micro-Lan.   Note that the center pin on the TO92 container is connected to the power ‘line’ –  the red (+) stripe while the remaining pins are connected to ‘ground’ – blue (-).

Breadboard wiring approach

50 node 1-wire network Micro-Lan - DS18B20 temperature sensors.

Test Controller – Arduino Uno – USB

Sample output from Arduino Code

Run time (sec/min/hr/9cycs): 15588/259/4/0 |  Elapsed: 15214 | Cnt: 412
>>###### ECLIPSE ########<<
Device Count: 50
Parasite power is: ON
Sleep ticks: 15500
Requesting temperatures...
* * * * * * * * * * * * * * * * * * * * *
>> 4:13:51 Thursday 1 Jan 1970 | Started: 0:00:00 Thursday 1 Jan 1970 <<
- - - - - - - - - - - - - - - - - - - - -
T-Sensor:   1 | 286053CE02000065 | C: 26.81 F: 80.26
T-Sensor:   2 | 28500DCE020000BF | C: 26.81 F: 80.26
T-Sensor:   3 | 28302CCE02000049 | C: 26.87 F: 80.37
... (snip) ...
T-Sensor:  49 | 287F25CE020000EB | C: 26.81 F: 80.26
T-Sensor:  50 | 28FF32CE0200002C | C: 26.81 F: 80.26
* * * * * * * * * * * * * * * * * * * * *
>> 4:14:11 Thursday 1 Jan 1970 | Started: 0:00:00 Thursday 1 Jan 1970 <<
- - - - - - - - - - - - - - - - - - - - -

Note about output above

Other notes – Coding & Arduino

Still on the list

1-wire Micro-Lan - 4 DS18b20 temperature sensors wired in parallel.

Topics: 1-Wire, Computer Technology, Fun!, Problem Solving, Unix-Linux-Os | Comments Off on 100 Node Micro-lan (DS18B20 Sensor Network)

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