Nick Electronics

POLAND • + Follow

Nick Electronics

POLAND
- 6
- 0
Engineer
- 0
- 0
Engineer

UNITED STATES OF AMERICA
- 0
- 0
Engineer

CZECH REPUBLIC, THE
- 0
- 0
5

Tools, APP Software Used etc.

	Altium Designer Altium Designer
	Microchip studio
	SolidWorks SolidWorks

Description

Minimalistic Soil Moisture Sensor

Youtube video -----> https://youtu.be/oqFGDM0aIfc

https://www.youtube.com/@NickElectronics

Description:

If you often forget to water your plants, this is a must-have device for you—a soil moisture tracker based on a PCB capacitive sensor and an ATmega48 microcontroller. Powered by two AAA batteries connected in series, the device can operate for two years without needing a battery replacement.

Functionality:

The device remains in sleep mode most of the time and wakes up every 10 minutes to measure soil moisture. If the soil is dry, it blinks red and then goes back to sleep. If the soil is sufficiently moist, it simply returns to sleep without blinking to avoid disturbing the user. When the battery is low, the device also signals this by blinking twice if the soil is dry or three times if the soil is moist.

Code

Code for the Soil Sensor V.1

C/C++

/*
 * SoilSensor.c
 */ 

#define F_CPU 8000000

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <stdbool.h>
#include <util/delay.h>

void sleep(void);
void wakeup(void);
void WDT (void);
void PWM_ON (void);
void LED_ON (void);
void LED_OFF (void);
void ADC_ON (void);
uint8_t read_adc(void);

uint8_t vin = 0; 
uint8_t sensor = 0;
uint8_t WDT_counter = 0; // each interrupt is 8 sec, so 600 sec is 75 interrupts

int main(void)
{
	WDT(); //enable WDT
	sleep(); // Go to sleep
	
    while (1) 
    {		
		if(WDT_counter >= 1) // If it`s been 600 seconds, proceed with the routine
		{	
			wakeup(); //Wake up from sleep, turn on all periphery
			_delay_ms(500);
			
			//Read batteries voltage. 1.1Vref internal source is used for the ADC
			ADMUX = 0b11100110;
			DDRD |= (1<<DDD1); // Connect voltage divider
			vin = read_adc(); // 193 value for 3.3V on batteries. 117 value when battery is at 2.0V level (discharged).
			DDRD &= ~(1<<DDD1); // Disconnect voltage divider

			//Read moisture level. Vcc as a voltage reference is used. This allows to read kinda same values when battery discharges.
			ADMUX = 0b01100111;
			sensor = read_adc(); // Read moisture level from the filter

			if(sensor >= 156) // Adjust to control moisture level. 203 is full dry. 110 is full wet
			{
				if(vin <= 117)// If battery is discharged blink twice 1 sec each time
				{
					LED_ON();
					_delay_ms(1000); // Use delays, cause why not. I don`t run any other important stuff in parallel :D
					LED_OFF();
					_delay_ms(1000);
					LED_ON();
					_delay_ms(1000);
				}
				else // If battery is above 2.0V just blink once for 2 seconds
				{
					LED_ON();
					_delay_ms(2000);
				}
			}
			else // If soil is moist enough go to this else
			{
				if(vin <= 117) // Blink 3 times fast if battery is discharged
				{
					LED_ON();
					_delay_ms(500); 
					LED_OFF();
					_delay_ms(500);
					LED_ON();
					_delay_ms(500);
					LED_OFF();
					_delay_ms(500);
					LED_ON();	
					_delay_ms(500);														
				}	
				else
				{
					LED_OFF();	// If battery is charged and soil is moist just keep LED OFF
				}			
			}	
			sleep();	//Go to sleep after all routine is done	
		}
		
		else // If it`s been less than 600 seconds, continue sleeping. 
		{
			sleep_enable(); 
		}
    }
}

void PWM_ON (void)
{
	// PWM
	DDRD |= (1<<DDRD6);
	PORTD &= ~(1<<PIND6);
	
	TCCR0A |= (1 << COM0A0); // Set OC0A on Compare Match
	TCCR0A &= ~(1 << COM0A1);
	
	TCCR0A |= (1 << WGM01); // CTC mode, top OCRA
	TCCR0B &= ~((1 << WGM02) | (1 << WGM00)) ;
	
	OCR0A = 10;
	
	TCCR0B |= (1 << CS00);
	TCCR0B &= ~((1 << CS01) | (1 << CS02));	
}

void PWM_OFF (void)
{
	// PWM
	DDRD &= ~(1<<DDRD6);
	PORTD &= ~(1<<PIND6);
	
	TCCR0A &= ~(1 << COM0A0); // Set OC0A on Compare Match
	TCCR0A &= ~(1 << COM0A1);
	
	TCCR0A |= (1 << WGM01); // CTC mode, top OCRA
	TCCR0B &= ~((1 << WGM02) | (1 << WGM00)) ;
	
	OCR0A = 0;

	TCCR0B &= ~((1 << CS01) | (1 << CS02) | (1 << CS00));
}

void LED_ON (void)
{
	DDRC |= (1<<DDRC2);
	PORTC |= (1<<PINC2);	
}

void LED_OFF (void)
{
	DDRC &= ~(1<<DDRC2);
	PORTC &= ~(1<<PINC2);	
}

void ADC_ON (void)
{
	DDRC &= ~(1<<DDRC1);
	DDRE &= ~((1<<DDRE3) | (1<<DDRE2));
	
	DIDR0=(0<<ADC5D) | (0<<ADC4D) | (0<<ADC3D) | (0<<ADC2D) | (0<<ADC1D) | (0<<ADC0D);
	ADCSRA=(1<<ADEN) | (0<<ADSC) | (1<<ADATE) | (0<<ADIF) | (0<<ADIE) | (0<<ADPS2) | (1<<ADPS1) | (1<<ADPS0);
	ADCSRB=(0<<ADTS2) | (0<<ADTS1) | (0<<ADTS0);	
}

void ADC_OFF (void)
{
	DDRC &= ~(1<<DDRC1);
	PORTC &= ~(1<<PINC1);
	
	DDRE &= ~((1<<DDRE3) | (1<<DDRE2));
	PORTE &= ~((1<<PINE3) | (1<<PINE2));
	
	DIDR0=(0<<ADC5D) | (0<<ADC4D) | (0<<ADC3D) | (0<<ADC2D) | (0<<ADC1D) | (0<<ADC0D);
	ADMUX = 0b00000000;
	ADCSRA=(0<<ADEN) | (0<<ADSC) | (1<<ADATE) | (0<<ADIF) | (0<<ADIE) | (0<<ADPS2) | (1<<ADPS1) | (1<<ADPS0);
	ADCSRB=(0<<ADTS2) | (0<<ADTS1) | (0<<ADTS0);
}
void wakeup(void)
{
	sleep_disable();
	cli();
	PWM_ON();
	ADC_ON();
}

void sleep (void)
{	
	cli();
	
	WDT_counter = 0;
	
	PWM_OFF();
	ADC_OFF();
	LED_OFF();
	
	set_sleep_mode(SLEEP_MODE_PWR_SAVE);
	sleep_enable();
	sei();                         //ensure interrupts enabled so we can wake up again
	sleep_cpu();
}

void WDT (void)
{
	cli();
	
    // Enable WDT with 8s timeout
    WDTCSR = (1 << WDCE) | (1 << WDE);  // Enable WDT configuration
    WDTCSR = (1 << WDP3) | (1 << WDP0); // Set prescaler for 8s timeout
	
	// Enable WDT interrupt
	WDTCSR |= (1 << WDIE);  // Watchdog Interrupt Enable

	sei();  // Enable interrupts
}

ISR(WDT_vect)
{
	WDT_counter++;
}

uint8_t read_adc(void)
{
	// Delay needed for the stabilization of the ADC input voltage
	for(int delay = 0; delay < 100; delay++){}
	// Start the AD conversion
	ADCSRA|=(1<<ADSC);
	// Wait for the AD conversion to complete
	while ((ADCSRA & (1<<ADIF))==0);
	ADCSRA|=(1<<ADIF);
	return ADCH;//ADCH;
}

Schematic and Layout

Schematic

SoilSensor.png

CAD-Custom parts and enclosures

Assembly

Assem1.SLDASM

Download Gerbers Download BOM(Bill of materials)

Jan 18,2025

1,087 views

Minimalistic Soil Moisture Sensor

I sometimes forget to water my plant, so I decided to make a soil moisture sensor to ensure I never forget again.

1087

10.00 (1)

Published: Jan 18,2025

Standard PCB

Download Gerber file 16

BOM(Bill of materials)

Centroid file

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File Last Updated: 2025/08/04 (GMT+8)

File update record

2025-08-0417:59:52

Centroid file is updated.

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