Soil Moisture and Water Level Sensor setup using LoPy4

[Roberto De Oliveira]

Hi there,

I am very new to pycom and IoT in general and I am looking to setup a soil moisture sensor and a Submersible water level sensor using Pycom LoPy4 with either an expansion board or a pysense board (depending on which board will work better in my application).

My plan is to setup 1 Davis soil moisture sensor with a LoPy4 x Expansion board/Pysense board, as well as, setup a 4-20ma signal submersible water level sensor on a separate LoPy4 x Expansion board/Pysense board.

My problem is I am struggling with finding the right circuitry setup to interface my sensors with the development boards. Everything I am finding seems extremely complicated and I was wanting to know if there is a simple example I could follow in order to setup these sensors.

You can find the links to the sensors I plan to use below:
https://www.davisinstruments.com/product/soil-moisture-sensor-vantage-pro-and-vantage-pro2/

https://www.robotics.org.za/KIT0139?search=submersible level

Thank you in advance for your help.

[Roberto De Oliveira]

Thank you for the assistance. I have a couple of issues I am trying to figure out and I was hoping someone could help. Apologies if these questions seems obvious and straightforward as my knowledge with electronics is very limited.

I plan to set these sensors up on a breadboard (and for as cheap as possible) and I am struggling with translating circuit diagrams/schematics over to a setup on a breadboard. As from my previous post, I plan to setup a resistive soil moisture sensor and a 4-20ma water level sensor and these both require some sort of circuitry to connect to the Pycom device. If anyone has an example I can follow and setup on a breadboard I would appreciate it greatly.

[kjm]

Sixty five bucks seems a lot for an old school gypsum block and they are a pain to read & calibrate. For a lot less $ you can a https://www.aliexpress.com/item/32849255839.html?spm=a2g0s.9042311.0.0.27424c4dr0bn9m soil moisture sensor that uses the same 4-20mA interface as your depth probe.

[livius]

It doesn't matter as long as you have enough free lines to connect all your sensors.
Only look if already attached sensors to some of expansion board do you need at all.
As all atached devices can consume some battery life.

[Roberto De Oliveira]

@livius Thank you for the help.

Do you an idea of which board (expansion or pysense) would work better with the sensors I have mentioned?

I plan to program my sensors to go in to deep sleep when not sensing so as to increase the battery life of the sensors for as long as possible,

[livius]

Hi

i do not dig much but:
for second of them you have diagram in the sensor description
https://i.ibb.co/mcBpN8K/KIT0139-005.jpg
but you must look at voltage levels as it looks like output is 5V range not 3.3V.
You can setup some voltage divider, e.g. simple one like https://ohmslawcalculator.com/voltage-divider-calculator
or use level shifter, you can use e.g. BSS138 or bigger model 2N7000

First one is simple resistance, you can measure it simply by some ADC line
Normally for such sensor there is some dedicated electronics which normalize it and do linear output like 100% 3.3V 50% 1.65V 0% 0V.
Without this electronic you must normalize it self and look at resistance in different situations.

To show exact wires look at this sample

and think that e.g. R1 is your sensor connected to 3V3 line