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Waterproof a capacitance soil moisture sensor: 11 steps (with pictures)

Capacitive soil moisture sensors are a great way to monitor soil water status in your potted plants, gardens or greenhouses using an Arduino, ESP32 or other microcontroller. They are superior resistance probes that are often used in DIY projects. Watch Andreas Spiess's video for a good explanation of how they work. The capacitance sensors cost only about $ 1 each in bulk, but they have exposed electronics and are not waterproof. A soil moisture sensor that cannot get wet is not very useful. This instructable shows you how to waterproof your sensors with glue-lined heat shrinkage, a small set of supplies and common tools.



  1. Capacitance soil moisture sensor, example from eBay, or from DFrobot
  2. Signal wire (at least 3 conductors), 22-24 meters; we used telephone cables from Lowes; It is a solid core 4-conductor so that a wire is not used.
  3. Glue lined polyolefin heat shrink tubes in three sizes: 1
    /4 ", 1/2" and 3/4 "diam. With at least 3: 1 shrinkage. Purchased on eBay for about $ 1 per foot (example
  4. ) : we used Sally Hansen Hard as nails from Target


  1. Wire Cutter (flush style)
  2. Wire Stripper
  3. Heat Gun
  4. Soldering Iron and Soldering
  5. Arduino or other microcontroller if you want test the sensor before and after mounting

Note: The most unusual item in this building is the large diameter heat shrink tubing with glue. Heat shrinkage is readily available from many suppliers. you buy your soil moisture sensors. Again, it must be glue lined and have a 3: 1 shrinkage ratio.

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