Wireless Weather Sensors

Overview

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

Needs:

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

Wants:

• 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?

Status

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

Operation

• 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.

Assembly

Slave

• A slave has all of the parts below

Master

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

Parts

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