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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 tmeals on Sat May 09, 2020 11:51 pm

Come to think of it, the reading of 1015 on the moisture sensor has to relate to the temperature. Every time the temperature dips below around 79-80F, the moisture reading tends to spike to 1015 and not give an accurate reading.

tmeals
 
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Re: STEMMA Soil Moisture Max Reading

by eipe on Tue Jun 02, 2020 10:25 am

Hello there, new here.

I have the exact same problem. Output 1015 in dry soil and 1015 in wet soil. 300-400 in air.

adafruit_support_bill wrote:Re-flashing the firmware requires a JTAG programmer. But we can just replace the sensors.

Please contact support@adafruit.com with a link to this thread. And let us know how the new firmware works for you.


What do I have to do re-flash the firmware?

1. Buy a JTAG programmer (how do I know if it's compatible, or are they all?)
2. Then what..? Is it super-complicated? I have experience of using VS Code and PlatformIO for programming Arduino etc. but this seems like a "low level" thing

I can try with wrapping some plastics around the sensor. But else, should I just email my address / issue and then you'll send the replacement? I'm a teacher situated in Sweden

eipe
 
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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Tue Jun 02, 2020 10:55 am

If your sensors were purchased recently, they already have the updated firmware. But we still see cases where the sensors become overloaded in some types of soil. Wrapping the sensor in a few layers of waterproof tape or heat-shrink decreases the sensitivity to where you can get better readings.

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Re: STEMMA Soil Moisture Max Reading

by cmcg on Sat Jun 20, 2020 12:32 pm

Regarding the volatility of the readings, I recently moved my setup to running of a lithuim ion battery pack and saw a huge decrease in the volatility:

Screenshot 2020-06-20 at 17.12.46.png
Screenshot 2020-06-20 at 17.12.46.png (917.41 KiB) Viewed 41 times


Yellow is the raw read from the sensor, blue gives a normalised percentage.

We're running off a pizero, and have tried multiple mains powered adapters,including the official one with no luck. Different battery packs produce the same consiten values.

Running the sensor wrapped in heatshrink, powered via a battery pack gives us a pretty decent reading. Below we get a clear decline in moisture level, and its obvious when the plant was watered:

Screenshot 2020-06-20 at 17.20.12.png
Screenshot 2020-06-20 at 17.20.12.png (348.63 KiB) Viewed 41 times


Any thoughts what would cause the difference between the powersupplies?

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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Sat Jun 20, 2020 12:40 pm

Most power supplies these days are switch-mode type supplies. These typically operate at fairly high frequencies and require filtering on the output to produce a steady DC voltage. Some have better filtering than others. Most have some residual switching noise on the output.

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Re: STEMMA Soil Moisture Max Reading

by tmeals on Sun Jun 21, 2020 2:07 pm

Regarding a fluctuating power supply -- would it be possible to put a capacitor in front of the STEMMA? If so, what size do you recommend?

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Re: STEMMA Soil Moisture Max Reading

by adafruit_support_bill on Mon Jun 22, 2020 5:09 am

A capacitor might help. A common strategy is to pair a small ceramic cap with a larger electrolytic to get the best characteristics of each:

https://www.adafruit.com/product/753
https://www.adafruit.com/product/2195

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Please be positive and constructive with your questions and comments.