Plant Monitor: Moisture

Part of the Projects section of Coddy's Arduino journey. Lesson 17 of 24.

This project watches a house plant: how wet its soil is, a coloured light for dry, fine or wet, an alarm when it stays dry, and a report on a screen.

A real build pushes a soil moisture sensor into the pot. It gives a voltage that changes with how wet the soil is, read with analogRead(). The simulator has no soil, so a potentiometer (a knob) on A0 stands in: turn it down for dry soil and up for wet. The sketch is the same either way.

A percent is easier to read than 0 to 1023: 0% is bone dry, 100% is soaking. map() converts one range into the other:

int reading = analogRead(A0);
int moisture = map(reading, 0, 1023, 0, 100);

Soil dries over hours, so one reading a second is plenty.

Challenge

Easy

Measure the soil:

write readMoisture(): read A0 and return the moisture in percent with map()
in loop(), print it as Moisture: 42%, then wait 1000 ms

Press Run, turn the knob, then Check.

Try it yourself

// The knob stands in for a soil moisture sensor
const int sensorPin = A0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  // read the sensor, turn it into a percent, print it, wait a second

}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Projects

Practice on your own: Arduino playground