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24545 Views 5 Replies Latest reply: Feb 13, 2013 3:32 PM by bombledmonk RSS
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Jan 18, 2013 11:13 PM

Looking to build a wireless sensor network (low cost and low power coin cell operated)



I am looking at implementing a very low cost temperature sensor module (module cost less than 10$)

I wish to install these low cost sensors to sample the temperature and humidity on a highway that has sections 500m long. Along the 500 meters there are poles installed at a distance of 10 meters each one on both the sides of the highway lane.

At the end of the 500m I wish to place a receiver to collect the data from the nodes sampled at lets say 10 minutes each.

The number of nodes would be 500/10*2=100 nodes.


Nodes have very limited battery power and should be powered by a Coin cell battery that should last atleast 2 years.


Can anyone get me started on this . i am not sure if i should consider a mesh network or a star topology. Moreover what protocol should I adopt BTLE or ANT or Zigbee.


I have spent hundreds of dollars buying evaluation kits and am really confused as to what will be the best approach. Any help will be appreciable.



  • MicrochipRTCfr Journeyman 121 posts since
    Sep 4, 2012



    One possibility is to use a royalty free protocole (MiWi) to avoid paying the ZigBee fee....

    With MiWi P2P, MiWi and MiWi PRO you can build networks from 2 to 8000 nodes.

    You can select the transceiver according to your needs (2.4GHz or 915MHz) : MRF24J40MA/MB/MC or MRF89XAM9A

    These modules are certified and operate in the -40 to +85C range


    Wireless Development Studio (Free) will help you configure and develop your application.

    Using ZENA sniffers (2.4GHz or 915MHz) together with WDS you can see packets


    The MiWi protocole can be implemented in any PIC18/PIC24F microcontrollers. There are many XLP variants which have extremely low standby currents (< 100nA) in the same magnitude order as the modules above.


    MiWi has a very small memory footprint (much smaller than ZigBee)...


    You can attend regular live online trainings or presential trainings by registering here to help you getting started fast with Microchip Development environment and architectures.



  • MicrochipRTCfr Journeyman 121 posts since
    Sep 4, 2012



    On the MiWi webpage you can find many of the shelf tools to evaluate MiWi networks :



    • Each set comes with 2 nodes. MiWi P2P, MiWi and MiWi Pro differnetiate themsevles only from SW viewpoint.
    • i.e with the same demoboards you can implement an end device, a coordinator and even a pan coordinator. Most boards have a PIC18F46J50 microcontroller which includes 64KB of flash (much more than needed to implement any type of node)
    • The Microchip libraries have several applications for MiWi networks in source code
    • With WDS you can develop and see the packets.
    • In case you need more performance, the nice thing about MiWi is that you can select between 8/16/32 bits devices as this protocole is running on all these architectures.


    In the libraries there are some projects whih implement SLEEP mode and as far as I remember also FREEZE mode





  • MetMan Journeyman 93 posts since
    Oct 24, 2011

    Getting under $10 for a microcontroller, radio module, and temp & humidity sensors will be pretty dificult.  The option that comes to my mind for the microcontroller + radio + temp sensor is Texas Instruments CC110L boosterpacks with their LaunchPad MSP430 boards.  This would only cost about $13.90 per unit, but you'd have to add a humidity sensor, the battery, and still put it in some type of weatherproof enclosure.

  • bombledmonk Novice 24 posts since
    May 14, 2012

    Digging up an old thread, but humidity sensors alone often don't get much below $4 or $5 in quantity and $8 in low quantities like your your application.   And as MetMan alluded to, a properly designed enclosure that's able to let in humidity and not the rest of the elements might be a tough proposition.  That's not even getting into FCC certification or buying modules that are able to carry FCC cert through the whole design. 

    There's a reason why Digi International and other companies charge what they do for ready-to-go sensor networks.  They really do cost a lot to make and bring to market.


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