Soil Moisture Sensor YL-69 or HL-69 interfacing with pic microcontroller, In this post you will learn how to interface Soil Moisture Sensor YL-69 or HL-69 with pic microcontroller? How to measure soil moisture using these low price sensors and how to display these measured values on liquid crystal display. Soil moisture sensor is also know as hygrometer. It is used to measure the humidity level of moisture or it is used to measure the moisture content in soil. You can also use it to measure water level by using multiple moisture sensors. you may also like to check our previous posts on various sensors interfacing with pic microcontroller.
- Flame sensor interfacing with pic microcontroller
- DHT11 humidity sensor interfacing with pic microcontroller
- PIR motion sensor interfacing with pic microcontroller
- Light dependent resistor interfacing with pic microcontroller
Table of Contents
Introduction to Soil Moisture Sensor YL-69 or HL-69
So now let’s see what is soil moisture sensor? How soil moisture sensor works? Pin out of Soil moisture sensor we are using in this post. As I have discussed earlier Soil Moisture Sensors are used to measure level of moisture in soil. I am using Soil Moisture Sensor YL-69 or HL-69 in this post. So now lets see how to use this senor. Picture of soil moisture sensor is shown below. It consists of two parts one is electronic circuit on the right side of the picture which is used to adjust the sensitivity and other on the left hand side consists of two probes which we place in soil. 
How to use a very interesting soil moisture sensor with pic microcontroller. let’s get started and let’s say wanted to use the sensor for a longtime since I find it quite an interesting one the sensor is very cheap. It costs around two dollars.The sensor can measure the levels of moisture in the soil so it can be extremely useful if you want to monitor the soil moisture of your plants or automate the watering procedure. let’s see the project we are going to build today I have one cup with me with dry soil if I place the sensor in the cup. we can read a low soil moisture value at 16×2 LCD display. if I pour some water in the cup you will see that the moisture levels rise and we can visually check the moisture levels of the soil of course. This is just a demonstration of the sensor I am going to build more useful projects in the future with this sensor.
Working of Soil moisture sensor
Let’s now see how to build this simple project the two large exposed pads function as probes for the sensor the more water in the soil the better the conductivity between the pads that results in a lower resistance the sensor is an analogue one so in the analog output. we get about that as the soil gets drier, we get more voltage at the analog output since the resistance between the probes gets higher we can set a threshold in order to enable the digital output at a certain moisture level using this potentiometer given with electronics part of sensor. But in this post, I am using only the analog output of the sensor module.
Pin out of Soil moisure sensor
The pin out soil moisture sensor is given below. The connection to pic microcontroller extremely easy as follows:
- we connect the ground of the sensor to ground pin of power supply.
- VCC pin of sensor to 5v of power supply voltage.
- Next we connect the analog output of the sensor to analog pin 0 of the pic microcontroller.
Interfacing with PIC16F877A microcontroller
PIC16F877A microcontroller is used in this post. PIC16F877A microcontroller has built in analog to digital converter. Analog output of sensor is connected with analog input of PIC16F877A microcontroller. PIC microcontroller reads sensors data and displays it on LCD. Then all we have to do is to connect the LCD display with PIC16F877A. after everything is connected we power up pic microcontroller and as you can see after a few seconds in the display we can see the moisture value of the soil now let’s see the code of the project. If you don’t know how to connect LCD with pic microcontroller, check this post:
- How to interface LCD with PIC16F877A microcontroller
- How to measure analog voltage with PC16F877A microcontroller
LCD prints out the value in percent the code is very simple we read the analog value from the sensor and we convert it to a value from 0 to 100 where zero is dry soil and 100 is wet soil then all we do is to print that value on the LCD display as always you can find the code of the project in the at the end of the article. That’s how easy it is to measure the moisture of the soil using this sensor it is a very interesting sensor and very useful as well.
Programming of moisture sensor measurement with PIC16F877a
Code for this project is written using Mikro C for pic compiler. You will upload code to pic microcontroller using pic kit 3 programmer.
// LCD module connections
sbit LCD_RS at RC0_bit;
sbit LCD_EN at RC1_bit;
sbit LCD_D4 at RC2_bit;
sbit LCD_D5 at RC3_bit;
sbit LCD_D6 at RC4_bit;
sbit LCD_D7 at RC5_bit;
sbit LCD_RS_Direction at TRISC0_bit;
sbit LCD_EN_Direction at TRISC1_bit;
sbit LCD_D4_Direction at TRISC2_bit;
sbit LCD_D5_Direction at TRISC3_bit;
sbit LCD_D6_Direction at TRISC4_bit;
sbit LCD_D7_Direction at TRISD5_bit;
////// Moisture sensor variable///////
float moisture_value;
char text[10];
void main(void)
{
ADC_Init(); // it will initialize the adc module of pic16f877a microcontroller
Lcd_Init(); // Initialize LCD
Lcd_Cmd(_LCD_CLEAR); // Clear display
Lcd_Cmd(_LCD_CURSOR_OFF); // Cursor off
Lcd_Out(1,1,"Moistue sensor" ); // Write text in first row
while(1)
{ // Endless loop
moisture_value = ADC_Read(0); // It will read the moisture value of sensor
moisture_value = ( moisture_value * 100) / (1023); // it converts the moisture value on percentage
FloatToStr(moisture_value, Ltrim(text));
Lcd_Out(2,1, text );
Lcd_Out_cp("%");
}
}
Simply upload this code to pic16f877a microcontroller and check working of your sensor.
