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STEMMA Soil Moisture Max Reading
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Re: STEMMA Soil Moisture Max Reading

by karlwachs on Mon Feb 10, 2020 10:16 am

the one that came in the flower pot ;)

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Re: STEMMA Soil Moisture Max Reading

by karlwachs on Mon Feb 10, 2020 11:24 am

.. its seems to be not very dense..

I believe you need to add a sensitivity multiplier to the code.

The user should be able to change it through the i2c commands.

When putting some layers of liquid plastics onto the sensor it seems it gets less sensitive and the lower value drops a little. So I will try to add 1 cm of non conducting insulation around it and then check again

Karl

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Re: STEMMA Soil Moisture Max Reading

by karlwachs on Mon Feb 10, 2020 12:00 pm

here some test results:
with ~ 3mm electric tape(both sides) + thin cover of liquid tape
inserted fully (up to the mark):
air: 335
glass of water: 530
water in metal can (m i l k froth pitcher ~10cm wide): 689 ( guess that's the max )
in hand firmly pressed: 675
dry soil: 652
wet soil: 682

that gives me a range of 650..682 -- not very good , but at least not always in overflow

Karl

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Re: STEMMA Soil Moisture Max Reading

by karlwachs on Mon Feb 10, 2020 6:50 pm

made the tape a little thinner (4.5mm as compared to ~ 6mm before),

now the range is ~700-900 in soil

Karl

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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Mon Feb 10, 2020 6:56 pm

The sensor response varies with different soil types. I'm going to set up some experiments with different types to get an idea of the range of response. If you can give me some idea of the composition of the soil you are using I will attempt to replicate your results here.

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Re: STEMMA Soil Moisture Max Reading

by karlwachs on Mon Feb 10, 2020 7:08 pm

here you go:
Image

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Re: STEMMA Soil Moisture Max Reading

by karlwachs on Mon Feb 10, 2020 7:10 pm

ps why is "m i l k" word forbidden? have to use spaces . it seems to be a dirty word ??

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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Mon Feb 10, 2020 8:13 pm

Thanks for the photo. I'll see what I can find at the local garden store.
ps why is "m i l k" word forbidden? have to use spaces . it seems to be a dirty word ??

We get a pretty constant barrage of spam with all kinds of weird content. Sometimes our automated filters pick out some odd words to ban.

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Re: STEMMA Soil Moisture Max Reading

by ashakeel on Wed Feb 19, 2020 12:13 am

Hi,

I have a similar issue with the sensor. I have three of them installed and they (almost always) all read ) 1015 in slightly wet and from-the-bag soil. They are read using a raspberry pi zero which is at least a foot away form them. I'd be happy to find a way to get around this.

Thanks!

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Re: STEMMA Soil Moisture Max Reading

by karlwachs on Wed Feb 19, 2020 12:53 am

wrapping them into ~ 1mm electric tape(pure plastic, no metal) reduces sensitivity and gets them into range from overflow(1015)

mine work now from ~ 600-900 for dry .. wet

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Re: STEMMA Soil Moisture Max Reading

by cmcg on Thu May 07, 2020 4:30 pm

I'm having hte same issue with 5 different sensors. Was the only solution here to wrap the sensor in plastic?

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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Thu May 07, 2020 6:23 pm

In some soils the sensors do tend to saturate quickly. I've had good luck wrapping with a couple layers of Kapton tape.

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Re: STEMMA Soil Moisture Max Reading

by cmcg on Fri May 08, 2020 12:49 pm

After significant testing using various solutions & soil mixtures I was still unable to get the sensor to perform as described (200-2000 range).

Best solution we've got so far is to encase the entire sensor in 3:1 adhesive heatshrink at about 1mm thick and 12.5mm diameter. Has the added advantage of waterproofing the device.

Gives a range of around 350-950 in dry to saturated soil. In water the sensor still overflows at 1015.

Still seems like theres a fault here though and at the very least the product page should be updated to reflect that.

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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Fri May 08, 2020 2:42 pm

Thanks for the feedback. I will relay that to the team.

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Re: STEMMA Soil Moisture Max Reading

by tmeals on Fri May 08, 2020 3:03 pm

I've been graphing moisture readings using a Seesaw capacitive moisture reading sensor from a plant in my office for over a month now and have noticed a few patterns shown in the attached screenshot (from the past two weeks). For reference, the red dotted lines are sunset, the orange are sunrise. Moisture is on the left axis, temperature on the right. The blue annotation is when I added water.
  • During the daytime hours, readings are sporadic, returning to the 1015 number mentioned in other posts, but also bouncing as low as 960 in some cases
  • During the evening, there's less bouncing and most of the readings are in the 1015 range
  • As the soil dries out, it has fewer readings at 1015
  • The temperature reading is fairly accurate
  • After the watering event a few days ago, the soil is giving higher moisture numbers

The code takes a moisture reading every minute and posts it to an Influx time-based database, where it's graphed in Grafana.

This plant is sitting near a window in my office, which faces north, so gets very little direct sunlight. Opening or closing the window seems to have little effect on the soil readings, although I would assume the soil dries out faster with the breeze.

When I started this project, I assumed there would be a steady decline of moisture, then adding water would spike the readings again and the cycle would repeat.
Attachments
Screenshot from 2020-05-08 11-31-07.png
Screenshot from 2020-05-08 11-31-07.png (649.48 KiB) Viewed 54 times

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Please be positive and constructive with your questions and comments.