How to Use the Soil Hygrometer Module - Arduino Tutorial

In this tutorial we will use one soil hygrometer module to measure soil moisture of a pot.

The module can give us a digital signal when the soil need watering and this output can be adjusted by the potentiometer. Or it can give us an analog signal of current soil moisture!

In this tutorial we will use the analog signal output of this module and we will change it in percentage value. Finally we will print in serial monitor the current percentage value of soil moisture.

So, let's get started!

Step 1: What You Will Need

For this tutorial you will need:

• Arduino uno
• Breadboard
• Soil hygrometer module
• some breadboard cables

And some soil for testing

Step 2: The Circuit

The connections are pretty easy, see the above image with the breadboard circuit schematic.

Step 3: The Code

Here's the code, embedded using Codebender!

Try downloading the Codebender plugin and clicking on the "Run on Arduino" button to program your Arduino board. And that's it, you've programmed your Arduino with this sketch!

You can keep playing with that by clicking the "Edit" button and start making your own modifications to the code.

Step 4: Serial Monitor - Testing

Put the sensor in dry soil for testing. Press the connect button below to start the serial communication.

Now throw some water on the soil and observe how the value changes

Step 5: Well Done!

You have successfully completed one more "How to" tutorial and you learned how to use the saoil hygrometer module with Arduino.

Check this Arduino Automatic Watering System

I hope you liked this, let me know in the comments!

Comments

[Renfuyffyhgkghfjfkhfghgkfghkf]

why doesnt it work

[MattM422]

Out of curiosity, why did you constrain the hygrometer's analog value to a set of numbers and then map it to yet another set of numbers? Why not just deal with the analog value directly?

[britdub]

Hello again I'm trying to add a pump to this project operated via a relay on pin A1

but I'm having problems with the value being stuck at 100% after adding the lines

to switch the relay

/* Arduino Tutorial - How to use a Soil Hygrometer Module

Dev: Michalis Vasilakis // Date: 18/05/2016 // www.ardumotive.com */

//Constants

const int hygrometer = A0; //Hygrometer sensor analog pin output at pin A0 of Arduino

int pump = A1; //pump on off

//Variables

int value;

void setup(){

pinMode (pump, OUTPUT); //SETS PIN A1 as output

Serial.begin(9600);

}

void loop(){

// When the plant is watered well the sensor will read a value 380~400, I will keep the 400

// value but if you want you can change it below.

value = analogRead(hygrometer); //Read analog value

value = constrain(value,300,160); //Keep the ranges!

value = map(value,300,160,100,0); //Map value : 400 will be 100 and 1023 will be 0

// if (value = 0) digitalWrite(pump, HIGH); // sets the pump on

// if (value = 100) digitalWrite(pump, LOW); // sets the pump off

Serial.print("Soil humidity: ");

Serial.print(value);

Serial.println("%");

delay(2000); //Read every 2 sec.

}

[britdub]

found this to work hope it helps others

/* Arduino Tutorial - How to use a Soil Hygrometer Module

Dev: Michalis Vasilakis // Date: 18/05/2016 // www.ardumotive.com */

//Constants

const int hygrometer = A0; //Hygrometer sensor analog pin output at pin A0 of Arduino

int pump = A1; //pump on off

//Variables

int value;

int pumpvalue;

void setup(){

pinMode (pump, OUTPUT); //SETS PIN A1 as output

Serial.begin(9600);

}

void loop(){

// When the plant is watered well the sensor will read a value 380~400, I will keep the 400

// value but if you want you can change it below.

value = analogRead(hygrometer); //Read analog value

value = constrain(value,300,160); //Keep the ranges!

value = map(value,300,160,100,0); //Map value : 400 will be 100 and 1023 will be 0

pumpvalue = value;

if (pumpvalue < 1)

{

digitalWrite(pump, LOW); // sets the pump off

}

else if (pumpvalue >= 99)

{

digitalWrite(pump, HIGH); // sets the pump on

}

Serial.print("Soil humidity: ");

Serial.print(value);

Serial.println("%");

Serial.println ("pumpvalue:");

Serial.println(pumpvalue);

delay(2000); //Read every 2 sec.

}

[britdub]

hello I'm a noob and I'm having problems with errors

(sketch file) [arduino-tutorial] Soil hygrometer module.ino:25:17:error: expected expression
Serial.println(%);
^
(sketch file) [arduino-tutorial] Soil hygrometer module.ino:25:18:error: expected expression
Serial.println(%);
^
2 errors generated.

I'm using a arduino uno connected via usb

Regards

Stevie p

[SebastiaanJansen]

That's because it doesn't recogenize the % as a variable. Format it between quotation marks like this:

Serial.println("%");

[britdub]

thank you