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I remember with fondness the X-10 days, when you could connect your computer to every wall plate in your house, using power-line carrier to transmit signals to addressable receivers (with varying degrees of success).

OK, so maybe I don't need to turn on my microwave from my computer remotely, but I still think it would be cool to have a wireless controller scheme for some home automation, maybe even put a webcam on my Roomba, or some temperature sensors outside.

What is a sensible overall way to approach this? Wifi endpoints are really attractive, but they seem a little pricey. Are there alternative approaches using radio? Or is power-line carrier still the way to go?

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Check out the sparkfun wireless guide.

I've been playing with jeenodes for most of my low-end stuff and think it might be the best cost/power ratio. I get mine through modern device.

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For wireless comms inside a house, the Nordic nRF24L01+ chips (modules available from Sparkfun) or the TI CC2500 (modules available from TI) are ideal. They are quite cheap.

The TI modules actually come with sensor network software that is easily adapted for a particular application.

Leon

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ZigBee works quite well for sensor networks and home automation. ZigBee is the network layer for the physical and MAC layer defined in IEEE 802.15.4-2003.

  • The raw, over-the-air data rate is 250 kbit/s per channel (2.4 GHz band), 100 kbit/s per channel in the 915 MHz band, and 20 kbit/s in the 868 MHz band.
  • Transmission range is rougly 300ft (1mW) and 4000ft (60mW).
  • The basic channel access mode is "carrier sense, multiple access/collision avoidance" (CSMA/CA).
  • In the 2.4GHz band there are 16 channels each requiring 5MHz of bandwidth.
  • IEEE 802.15.4-2003 short (16-bit) and long (64-bit) address modes supported. bandwidth, low power network

There are number of ways to deploy ZigBee. Most people buy a system on a chip like an XBee that you talk to using a UART. The XBee integrates a uC, radio and antenna. You can use the XBee with a board like an Arduino or you in a standalone mode. In standalone mode the XBee can be set to periodically wake, collect data, transmit the data and go back to sleep. The XBee uC has digital I/O capabilities and an ADC. At a 0.1% duty cycle a couple of AA's will last 2-3 years. With some better power management longer battery life is easily possible.

I did a little write-up on ZigBee a few weeks ago. The write-up is at http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html

I also make a uC board that integrates an XBee with an Arduino compatible uC http://wiblocks.luciani.org/ZB1/index.html On my site are some XBee programming examples.

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