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.