Question about Soil Moisture Sensor

Projects General Guidance
1

Can someone tell me if the module connected to the soil moisture sensor is needed for my arduino due?
For example, in this random picture, I took from google,

I was planning on buying one of these soil moisture sensors, but I am not sure as they do not come with the module. I am not that sure what these blue modules do, but I was wondering if they are needed.
https://www.digikey.ca/en/products/detail/dfrobot/SEN0193/6588605
https://www.digikey.ca/en/products/detail/sparkfun-electronics/SEN-13637/7400839

2

I would guess that is an amplifier to bring the sensor readings up to reasonable voltage level, and perhaps output that in I2C bus. Can't see what the pins on the module are labelled.

3

found it on google ?
I think the consensus would be to put it back.

Try duckduckgo and search for chrip soil sensor.
there are a lot of knockoffs, I think most work, but the concept is that the sensor does not wear out.

the capacitive sensor is recommended over the soil resistance type.

4

The module contains an op-amp, probably an LM386, to amplify the tiny voltage differences to levels that the Arduino analog input can read.

This type of resistance-based moisture sensor needs to be replaced every growing season because the traces on the PCB oxidize and eventually become quite insensitive.

A capacitance moisture meter does not expose the sensor leads to the soil, so the oxidation of the probes is not a problem. But it's less sensitive. The resistance range of dry to moist soil is comparatively large while the capacitance change from dry to moist soil is pretty small.

5

SteveMann:
The module contains an op-amp, probably an LM386, to amplify the tiny voltage differences to levels that the Arduino analog input can read.

This type of resistance-based moisture sensor needs to be replaced every growing season because the traces on the PCB oxidize and eventually become quite insensitive.

A capacitance moisture meter does not expose the sensor leads to the soil, so the oxidation of the probes is not a problem. But it's less sensitive. The resistance range of dry to moist soil is comparatively large while the capacitance change from dry to moist soil is pretty small.

So it's needed I presume? I'm not that sure since I am just looking at the Connection Diagram of the datasheet for the GRAVITY: ANALOG CAPACITIVE SOIL.
I'm not sure what module would go with the sensor. Is any fine or just the LM386 that you said?

6

Please post a link to any parts you reference.

Capactive soil sensors typically output 0 to 5 volts with out additional components

7

kevhua36:
So it's needed I presume? I'm not that sure since I am just looking at the Connection Diagram of the datasheet for the GRAVITY: ANALOG CAPACITIVE SOIL.
I'm not sure what module would go with the sensor. Is any fine or just the LM386 that you said?

My mistake, it's an LM393 comparator.

Schematic

8

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