Project Description

We want to know the moisture level across a .2 acre garden. For cost-effectiveness and simplicity, we're building multiple inexpensive sensors. The sensors blink at a moisture-dependent rate. A user visually inspects each sensor recording the blink rate and uses the data to determine the moisture level in the garden.

Project Notebook

  • [22 Sep 2010] We added moisture to Sample A during our experiment. Sample A has been marked as Sample A', and Sample B has been marked as Sample B'. Both samples will remain at Quelab for testing.
  • [22 Sep 2010] sample A is blinking at 1 blink per 8 seconds. Sample B is not blinking.
  • [22 Sep 2010] I took an A and B sample from the garden at Sunflower River. Sample A is from a dry part of the garden, Sample B is from a moist part of the garden. Visually, Sample B is more moist than Sample A.
  • [Sep 2010] Testing with commercial soil from a planter outside of Quelab.
  • [Aug 2010] Sunflower River and Quelab have started a project to test soil moisture levels in the garden at Sunflower River.

Project Design

The current circuit we are working from, is this 1.5v flasher with the megaohm resistor in series with a simple soil sensor.

Soil Moisture Sensor


  • need to invert the blink, so it blinks more when drier, far more intuitive, im thinking a resistor bypassing the BC557 might make it a comparator. But i'm totally not sure, very rusty on all this!
  • May also need a wheatstone bridge for calibration/sensitivity adjustments
  • Need to source sources for fabricating the circuit board cheaply
  • packaging, going to try and heatshrink a coke bottle. around a form, sofar my idea is to build sensor and circutry through a bottle cap leaving a shrunken bottle for weatherproofing/protecting the circuit/battery
  • need a accurate small scale, so we can measure dirt, dry/wet to get moisture content
  • Cast simple averaging sensors
    • attach wires to 2 stainless steel screws.
    • screw through plastic bottle cap(poking outwards, wires inside the bottle)
    • insert screws into liquid plaster in a mold. let cure 24hours.
    • Remove from mold and let dry in sun,

Project Members