Sunday, 15 January 2012

Home Wireless Sensor Network - Making Plans

My current main project is to build a wireless sensor network. However, for various reasons I am currently blocked from doing any real work on this project - so I thought I would blog about my plans instead!

The goal of this project is to be able to take readings from wireless nodes placed around my house (and possibly in my garden). This provides the following requirements.
  • I want to build 5-10 of these sensor nodes so they need to be very cheap.
  • I need to be able to place them wherever is best for measurements without regard for plug sockets so they need to be battery powered.
  • I don't want to be replacing 5-10 batteries a week so they need to be very low power so that they can run for a few months between each battery change.
  • Each node should be able to collect multiple readings although initially they will all only collect temperature.

To meet these requirements I plan to combine the following into a single wireless sensor node.

  • ATTiny85 (~£1.50) microcontroller
  • TMP36 (£1.50) temperature sensor
  • RF Link Transmitter (~£1.50)
  • Tripad stripboard (£4/sheet, need ~1/4 of a sheet, hopefully less)
  • Battery holder (£1)
  • Batteries (~£4)

This comes to a grand total of about £11 for a single wireless node. This seems to be about as cheap as you can get it.

The rest of the setup will be made of the following parts.
  • An Arduino base station receives the readings from all of the wireless sensor nodes and writes them to SD card.
  • A Raspberry Pi connects to the Arduino over Bluetooth and downloads the stored readings. The Raspberry Pi connects to the internet over Wifi and uploads the readings to Pachube.

Here's a picture of a Raspberry Pi because every blog post should have a picture.

I also have plans to build a physical display to show the latest readings.

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