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.
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)...
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Hi and thanks for the details. I have looked up details on MiWi and would like to try building a few sensor nodes. Now my problem is that i cannot find a prebuilt circuit board that has the RF and Microcontroller electronics. Any advise on where to look would be useful.
It would be nice to have coin cell operable boards that can be programmed once and let go. Also could you recommend similar hardware boards for gateway devices, coordinators etc.
On the MiWi webpage you can find many of the shelf tools to evaluate MiWi networks :
In the libraries there are some projects whih implement SLEEP mode and as far as I remember also FREEZE mode
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.
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.