STEMMA Soil Moisture Max Reading

General project help for Adafruit customers

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

the one that came in the flower pot ;)

User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

.. 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

User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

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

User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

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

now the range is ~700-900 in soil

Karl

User avatar
adafruit_support_bill
 
Posts: 88090
Joined: Sat Feb 07, 2009 10:11 am

Re: STEMMA Soil Moisture Max Reading

Post by adafruit_support_bill »

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.

User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

here you go:
Image

User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

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

User avatar
adafruit_support_bill
 
Posts: 88090
Joined: Sat Feb 07, 2009 10:11 am

Re: STEMMA Soil Moisture Max Reading

Post by adafruit_support_bill »

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.

User avatar
ashakeel
 
Posts: 1
Joined: Thu Oct 12, 2017 12:48 am

Re: STEMMA Soil Moisture Max Reading

Post by ashakeel »

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!

User avatar
karlwachs
 
Posts: 33
Joined: Thu Jan 14, 2016 7:42 pm

Re: STEMMA Soil Moisture Max Reading

Post by karlwachs »

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

User avatar
cmcg
 
Posts: 4
Joined: Thu May 07, 2020 4:29 pm

Re: STEMMA Soil Moisture Max Reading

Post by cmcg »

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

User avatar
adafruit_support_bill
 
Posts: 88090
Joined: Sat Feb 07, 2009 10:11 am

Re: STEMMA Soil Moisture Max Reading

Post by adafruit_support_bill »

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

User avatar
cmcg
 
Posts: 4
Joined: Thu May 07, 2020 4:29 pm

Re: STEMMA Soil Moisture Max Reading

Post by cmcg »

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.

User avatar
adafruit_support_bill
 
Posts: 88090
Joined: Sat Feb 07, 2009 10:11 am

Re: STEMMA Soil Moisture Max Reading

Post by adafruit_support_bill »

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

User avatar
tmeals
 
Posts: 3
Joined: Tue Jun 04, 2019 12:37 am

Re: STEMMA Soil Moisture Max Reading

Post by tmeals »

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 287 times

Locked
Please be positive and constructive with your questions and comments.

Return to “General Project help”