I buy parsley in pot, and most of day, soil were dry. So I decide to make this project, about sensing moisture of soil in pot with parsley, to check, when I need pour soil with water.
I think, this sensor (Capacitive moisture sensor v1.2) is good because:
1. has waterproof electrodes, so you don't worry about corrosion.
2. is cheap -> 1,5 - 2 $
Step 1: BOM
Bill of materials (affiliate links, if you want buy this materials, you can support me, if you buy through this links):
1. Capacitive moisture sensor v1.2.
2. Wemos D1 Mini.
Link: Wemos D1 Mini
3. ADS1115 for measure analog values from sensor.
4. Battery - I use 18650, lithium - ion battery.
(In past , I bought trustfire mark. Good battery has own code to recognize original)
5. Battery holder (you can cut out one side, for better put in battery to holder)
Link: Battery holder
6. Cables . I use AWG 22 type.
Of course, you need soil for measure :D
Step 2: Circuit
I do classic circuit. Firstly, I power Wemos with 4,2 volts from lithium battery. It is possible, and I connect it to 5V pin. It works, without neccesary of regulator!
Deep sleep current is under 0,3 mA.
For powering sensor and ADC, I use pin 8 from wemos. Very important is using constant voltage (3,3 V) and do not use battery (where voltage change from 3 volts to 4,2 volts)
Step 3: Code
I use ThinkSpeak as store data. I use 10 minutes intervals.
Don't forget to connect Reset pin with D0 to restart wemos after sleeping. I created diagram to show how code work.
Code in Arduino:
Step 4: Final
If you will build circuit, please use longer cables. Not like me.
Step 5: Testing
For measure moisture, use cca 3/4 of sensor's surface. Be care, and don't pour sensor with water.
I use Thingspeak for saving values. I can say, that values depend on temperature, so monitoring of temperature should be good.
I started to measure 25. March dinner (I pour parsley) and then I wait. During night day, values not chaning.
In 26. March, values rise up as temperature rise up. But next night (from 26. March to 27. March), values were higher. So soil in pot were drier (more arid)