what kind of sensor can i use for soil

Discussion in 'The Projects Forum' started by mohsen, Feb 12, 2011.

  1. mohsen

    Thread Starter Active Member

    Oct 24, 2008
    hi, i'm building a project that if the soil humidity is low the sensor will send me signal!!
    if any one can help me for the right sensor!!! to use in my circuit!
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    Probes to go into houseplant pots are often simply two metal rods at a fixed spacing which are pushed 4-6 inches into the soil. Then the resistance is measured. It's more of a conductance (Siemens, inverse of resistance) than resistance, as the value is very high, and has a wide margin based on soil type.

    Is this for houseplants, lawns, or crop irrigation?
  3. mohsen

    Thread Starter Active Member

    Oct 24, 2008
    it's for crop irrigation, is there more simple thing like i don't know a chip!
  4. jdraughn

    Active Member

    Jan 30, 2009
  5. wayneh


    Sep 9, 2010
    You can buy increasingly accurate and reliable devices starting at ~$4 USD and moving up to several hundred dollars. The cheap ones all use the conductivity approach already mentioned, and you can build your own if you want. More costly meters use other means. The ultimate would be a laboratory measurement of water activity.

    Since you are concerned about a large area, using multiple cheap sensors might be useful.