How to calibrate a low cost moisture/water-content sensor for hydroponics

In this video, I show you how I calibrate a low-cost capacitive sensor to measure the water content (as % of total potential water held by the media) of a hydroponic medium (in my test case, rice hulls mixed with river sand).

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Arduino MKR Wifi 1010

Capacitive moisture sensor sensor

Scale building kit

Beaker set

Ribbon cable package

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[monosero]

Struggled with getting those capacitive sensors working.
Now i ordered such scale and will try your method, thanks!

[MausSpaece]

Looking forward to seeing more Arduino/Raspi/MyCodo videos!!

[kengriest]

You could speed up and more thoroughly dry the media if it wasn't placed in the beaker, reducing the evaporative area of the sides of the net pot. Perhaps a petri dish or glass bowl would be better. Depending on the sensitivity of the scale, a fan blowing in the vicinity, but not directly at the apparatus, could also help reach the dry media endpoint.

[angreyman]

beyond thankful for this video, quick question is there a way to have my code translate the mv from the calibrated sensor to the moisture percentage or do you always have to plug it into that equation ??

[SetTheCurve]

I use ecowitt moisture sensors for my garden and I've found them horribly inaccurate. Bumping them even slightly will dramatically alter the reading. Changing to a different part of the pot changes the reading. Changing amounts of nutrient in the media I believe also modifies the reading. Do the sensors in this video perform well regardless of position in the media container? Do they perform well even if firm contact with the soil has been lost due to media shrinkage etc?

I religiously use mine, but I have to constantly take notes about what value means what. At the beginning of a season, I calibrate, and know to irrigate at 65%. A month later I might need irrigation at 40%, 20%, or 80%. It's really frustrating.

I've searched for hours and hours for an alternative product that performs well and does not cost a fortune.

[JRE]

Would one need to calibrate each individual sensor separately if you buy multiple of the same sensor, or can you use the same formula for each sensor?

[SetTheCurve]

If you maintain the substrate moisture at a constant saturation % and do not allow the substrate to cycle between dry and wet, will the plant suffer? I've always been under the impression that in irrigated hydroponics the dryback is necessary to give the roots an opportunity to breathe. I'm assuming that the O2 that follows the oxygenated nutrient solution is not enough all on its own. Thoughts?