From 2a67dfbb93a8304027bd275646ff8d06d0b0165d Mon Sep 17 00:00:00 2001 From: Administrator Date: Sun, 18 Aug 2024 08:54:20 +0200 Subject: [PATCH] docs: create waterproof_sensors --- waterproof_sensors.html | 94 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 waterproof_sensors.html diff --git a/waterproof_sensors.html b/waterproof_sensors.html new file mode 100644 index 0000000..5a66140 --- /dev/null +++ b/waterproof_sensors.html @@ -0,0 +1,94 @@ + + +

 

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Waterproofing a Capacitance Soil Moisture Sensor

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https://www.instructables.com/Waterproofing-a-Capacitance-Soil-Moisture-Sensor/

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Waterproofing a Capacitance Soil Moisture Sensor
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Supplies

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Parts:

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  1. Capacitance soil moisture sensor, example from eBay, or from DFrobot
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  2. Signal wire (at least 3 conductors), 22 -24 gauge; we used telephone wire from Lowes; it's solid core 4-conductor so one wire is not used.
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  3. Adhesive-lined Polyolefin Heat-shrink tubing in three sizes: 1/4", 1/2" and 3/4" diam. with at least 3:1 shrink. Purchased on eBay for about 1$ per foot (example).
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  4. Laquer or nail polish: we used Sally Hansen Hard as Nails from Target
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Tools:

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  1. Wire Cutter (flush style)
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  2. Wire Stripper
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  3. Heat Gun
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  4. Soldering iron and solder
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  5. Arduino or other microcontroller if you want to test the sensor before and after assembly
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Note: The most unusual item in this build is the large diam. heat shrink tubing with adhesive. Heat shrink is readily available from many suppliers. It's also on eBay, so you can buy your heat shrink when you buy your soil moisture sensors. Again, it must be adhesive-lined and have a 3:1 shrink ratio.

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Step 1: Get a Capacitance-based Soil Moisture Sensor and Test

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Get a Capacitance-based Soil Moisture Sensor and Test
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Get a Capacitance-based Soil Moisture Sensor and Test
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On rare occasions, we have found batches of these sensors that are flawed (we got a bad order from Ali Express). I would run a simple test of the sensors with an Arduino before waterproofing. There are many tutorials on the web - here is an example.

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Step 2: Remove the Connector

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Remove the Connector
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Remove the connector with a flush cutter. After the connector is removed, there will be three unused solder through-holes for attaching the signal wires (they cannot be seen until you remove the connector)

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Step 3: Prep Signal Wire and Solder to Sensor

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Prep Signal Wire and Solder to Sensor
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Prep Signal Wire and Solder to Sensor
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Prep Signal Wire and Solder to Sensor
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Prep signal wire and solder. Made sure to trim the wires on the back of the board flush with the PCB using your cutter. Clean the solder joint with rubbing alcohol.

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Step 4: Apply Lacquer (nail Polish) to Exposed Circuits

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Apply Lacquer (nail Polish) to Exposed Circuits
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Apply Lacquer (nail Polish) to Exposed Circuits
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Apply Sally Hansen's nail polish or a similar compound to exposed circuits on the front and back where the electronic components and traces are exposed. Do not apply to the whole sensor board, just the top inch or so with exposed electronics. Do this outdoors or in a well-ventilated room - allow 30 min to dry.

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Step 5: File the Corners of the PCB Sensor With Sandpaper or a File

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File the Corners of the PCB Sensor With Sandpaper or a File
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File the corners with sandpaper or a file. This prevents the sharp corner from piercing the heat shrink tubing

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Step 6: Prep Your Heat-shrink Tubing

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Prep Your Heat-shrink Tubing
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Cut three sectons of heat shrink tubing as follows.

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1/4" diam. - 1.25 inches long

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1/2" diam. - 0.75 inches long

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3/4" diam. = 1.5 to 1.75 inches long (I used 1 5/8")

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Step 7: Shrink the 1/4" Diameter Tubing First

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Shrink the 1/4
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Apply the 1/4 diameter tubing with the heat gun - as always - BE VERY CAREFUL WITH THE HEAT GUN. Get adult supervision if needed.

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Step 8: Add the 1/2" Diameter Heat-shrink Tubing

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Add the 1/2
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Add the 1/2 tubing with the heat gun.

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Step 9: Apply the 3/4" Diameter Heat-shrink Tubing

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Apply the 3/4
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Apply the 3/4
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Apply the 3/4
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Last, apply the 3/4" diameter tubing. Make sure the adhesive is melted and seals all the joints. It's important that you get the tubing in the correct position or you won't get full coverage of the electronics. Using a gloved hand, you can apply pressure to the heat shrink while it's still warm to push the adhesive onto the PCB; this may improve the seal.

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Step 10: Apply a Thin Layer of Nail Polish at the Sensor / Tubing Seam

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Apply a Thin Layer of Nail Polish at the Sensor / Tubing Seam
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Apply a thin layer of nail polish at the sensor / tubing seam to provide extra waterproofing protection.

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Step 11: Complete Probes and Test Again

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Complete Probes and Test Again
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Test the probes again with your Arduino or other microcontroller. I submerged my sensors in a glass of water for several days while taking readings periodically to verify performance.

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