Build a networked soil moisture sensor for your garden

If you are into gardening, this can be a fun project. Sometimes you forget to water plants and they droop. What if you could get an SMS on your phone reminding you to water the dehydrated plant.

You need the following for this project –

  • A simple moisture sensor. You can build a simple one yourself or buy one online. I have not found any in Bangalore yet.
  • At least two WiSense nodes. The “sensor” node will have a moisture sensor attached to it. The other node will be part of a “WiSense network <-> WiFi” gateway. The “sensor” node can be powered by a coin cell or could be solar powered if the node is going to be outdoors.

The challenge is in building a reliable soil moisture sensor. There are plenty of ideas on the net.   A simple sensor can monitor the electrical resistance between two nails embedded in the soil. Resistance decreases as soil moisture increases. The on board ADC on the MSP430 can be used to determine the resistance across the two conductors through a voltage divider circuit.

You need to write a simple application which will run on the “sensor” node’s micro-controller. This app can measure soil resistance periodically and send out an alarm message to the “gateway” node only when the  resistance value climbs above a threshold. It will take some trial and error to arrive at the correct threshold.  The application should keep sending alarms periodically until it detects a “watering” event (a sudden decrease in soil resistance).

I am wondering if temperature, humidity and ambient light sensors can help predict plant growth.

Posted on December 4, 2013, in Uncategorized. Bookmark the permalink. Leave a comment.

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