Wireless Weather Sensors

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Designed to be simple to build, low parts cost, and low maintenance.


  • Wirelessly transmit temperature and relative humidity to a main unit.
  • Run off a single AA, two AA, or a 9v battery


  • Two pins who's grounded status could be reported (think a door sensor, or something)
  • Two pins that could be set to send 3.3v or 5v to run an relay
  • Thermostat control?


In progress

  • Identify all components
    • Need opticron's help
    • Determine if any of the SHTx line would be better and cheaper than the DHT22
    • Figure out any additional components, pressure?
  • Identify an AVR
    • Validate with someone else
    • Determine total pin count needed for AVR
    • Identify cheapest AVR
  • Order components and AVR
  • Breadboard a prototype
  • Design PCB
    • Need crashcart's or mog's help
  • Order or print prototype PCBs
    • Need mog's help
  • Build first test prototype


  • Each unit will power up and listen for the sync signal from the master unit.
  • Once they get the sync signal, they listen for any other already established units to send their data.
  • Then they locate the next spot in the time slots.
  • Something about collisions
  • Something about the master allocating timeslots dynamically
  • Something about filling in blank timeslots.



  • A slave has all of the parts below


  • A master has all of the same parts
  • A master also piggybacks on an openmesh router or 802.11 device of some sort.


Name Price for 10 units AVR pins required Link Alt Link
RFM22B-S2 Wireless Transceiver $4.40 4(SPI) http://www.hoperf.com/rf_fsk/RFM22B.htm
DHT22 Humidity and Temperature Sensor $8.96 1 (i think) http://www.sparkfun.com/products/10167
BMP085 - Pressure Sensor  ?  ?  ?
Battery case  ?  ?  ?

AVR possibilites:

Model I/O Pins Price per 10 Link
ATTINY84 12 $3.01 http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ATTINY84-20PU-ND
ATTINY4313 18 $2.80 http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ATTINY4313-PU-ND