Adafruit STEMMA Soil Sensor - I2C Capacitive Moisture

Using Arduino Project Guidance
1

Hello,

I am new to the world of Arduino (with some experience and guidance from a couple of years ago that has not been developed further since), and need some general advice on how to approach the following project.

I am running some experiments in a small greenhouse where I need to monitor the soil moisture of 56 pots over the span of 6 weeks. The way I have divided the monitoring system is using 8 Arduino Uno Rev3 boards, each being connected to 7 soil moisture sensors (Adafruit STEMMA Soil Sensor - I2C Capacitive Moisture Sensor). Based on readings I have done on the adafruit website and forums, my understanding is that I would need a multiplexer (TCA9548A I2C Multiplexer) in order to create individual addresses for each sensor. Up to this point, it seems pretty straightforward. I am attaching the sketch of the assembly.

My question is whether I need any resistors and if I need to add the Adafruit LTC4311 I2C Extender / Active Terminator - STEMMA QT / Qwiic to the circuit. The individual wires between the sensors and the breadboard won't be longer than 2ft each.

Any feedback would be greatly appreciated!

Arduino - Multiplexer-01
Arduino - Multiplexer-011920×1484 189 KB

2

I'm not very familiar with I2C yet, so I can't help you there. It is my understanding that Adafruit integrates all the pull up/down resistors into their hardware. Double check the power draw of everything and what the Arduino can supply. You may be well within spec, but since you'll have 8 devices I think it's worth checking.

3

Try a separate STEMMA, if it works for you then you don't need the TCA9548A I2C.
In your diagram you do not have connected the control pins of the Mux that you are using, you need those to "select" which sensor you are going to read.
I have an idea to read the humidity in the soil of the 56 pots using a single Arduino UNO R3, if you are interested let me know.

1 Like
4

Hey bud, i have same issues
I need to connect 20 soil moisture sensors to an Arduino Mega 2560 via Multiplexer and show the percentage. Any idea how to to that?

5

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.