Soil moisture sensor in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read the soil moisture sensor value.

Arduino

int sensorValue = analogRead([1]);

Drag options to blanks, or click blank then click option'

AA0

B13

CGND

D5V

Attempts:

3 left

💡 Hint

Common Mistakes

Using a digital pin number instead of an analog pin.

Trying to read from power or ground pins.

The soil moisture sensor is connected to analog pin A0, so we use analogRead(A0) to get its value.

2fill in blank

medium

Complete the code to print the sensor value to the serial monitor.

Arduino

Serial.println([1]);

Drag options to blanks, or click blank then click option'

Amoisture

BsensorValue

Csensor

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that was not declared.

Printing a string instead of the variable.

The variable holding the sensor reading is sensorValue, so we print that.

3fill in blank

hard

Fix the error in the code to initialize serial communication at 9600 baud.

Arduino

Serial.begin([1]);

Drag options to blanks, or click blank then click option'

A9600

B115200

C4800

D19200

Attempts:

3 left

💡 Hint

Common Mistakes

Using a baud rate that does not match the serial monitor setting.

Using a very high baud rate without hardware support.

The standard baud rate for many Arduino serial communications is 9600.

4fill in blank

hard

Fill both blanks to create a condition that checks if the soil is dry (sensor value less than 300).

Arduino

if ([1] [2] 300) {
  Serial.println("Soil is dry");
}

Drag options to blanks, or click blank then click option'

AsensorValue

B<

C>

DmoistureLevel

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name.

Using the greater than operator instead of less than.

We check if sensorValue is less than 300 to detect dry soil.

5fill in blank

hard

Fill all three blanks to map the sensor value (0-1023) to a percentage (0-100) and print it.

Arduino

int moisturePercent = map([1], 0, [2], 0, [3]);
Serial.print("Moisture: ");
Serial.print(moisturePercent);
Serial.println("%");

Drag options to blanks, or click blank then click option'

AsensorValue

B1023

C100

DmoistureValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect variable names.

Mixing up the input and output ranges.

The map function converts the sensor reading from 0-1023 to 0-100 percent.

Practice

1.

What does the analogRead() function do when using a soil moisture sensor with Arduino?

easy

A. It prints the sensor value to the serial monitor.

B. It reads the sensor's analog voltage value representing soil moisture.

C. It sends power to the soil moisture sensor.

D. It converts the sensor value to a digital HIGH or LOW.

Solution

1. Step 1: Understand the purpose of analogRead()

   The analogRead() function reads the voltage from an analog pin and returns a value between 0 and 1023.

2. Step 2: Connect to soil moisture sensor output

   The soil moisture sensor outputs an analog voltage that changes with moisture level, which analogRead() captures.

3. Final Answer:

   It reads the sensor's analog voltage value representing soil moisture. -> Option B

4. Quick Check:

   analogRead() reads analog sensor value [OK]

Hint: analogRead() always reads voltage from analog pins [OK]

Common Mistakes:

• Thinking analogRead() sends power to sensor
• Confusing analogRead() with Serial.println()
• Assuming analogRead() returns digital HIGH or LOW

2.

Which of the following is the correct way to read a soil moisture sensor connected to analog pin A0 and print its value?

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

void loop() {
  int moisture = ?;
  Serial.println(moisture);
  delay(1000);
}

easy

A. moisture = analogRead(A0);

B. moisture = digitalRead(A0);

C. moisture = Serial.read(A0);

D. moisture = analogWrite(A0);

Solution

1. Step 1: Identify correct function to read analog sensor

   Use analogRead() to read analog pin A0 for sensor value.

2. Step 2: Confirm syntax matches Arduino standards

   The correct syntax is moisture = analogRead(A0); to store the sensor value.

3. Final Answer:

   moisture = analogRead(A0); -> Option A

4. Quick Check:

   Use analogRead() for analog sensor input [OK]

Hint: Use analogRead() for analog sensors, not digitalRead() [OK]

Common Mistakes:

• Using digitalRead() for analog sensor
• Trying to use Serial.read() to get sensor value
• Using analogWrite() which outputs voltage, not reads

3.

What will be printed to the Serial Monitor when this Arduino code runs if the soil moisture sensor reads 512?

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

void loop() {
  int moisture = analogRead(A0);
  Serial.println(moisture);
  delay(1000);
}

medium

A. 0

B. 1023

C. 512

D. AnalogRead Error

Solution

1. Step 1: Understand analogRead() output

   analogRead() returns a value between 0 and 1023 based on sensor voltage. Here it reads 512.

2. Step 2: Serial.println() prints the value

   The code prints the value stored in moisture, which is 512.

3. Final Answer:

   512 -> Option C

4. Quick Check:

   analogRead() value printed = 512 [OK]

Hint: Serial.println() prints the sensor value read by analogRead() [OK]

Common Mistakes:

• Expecting maximum 1023 always printed
• Thinking analogRead() returns 0 or error
• Confusing analogRead() with digitalRead() output

4.

Identify the error in this Arduino code snippet for reading a soil moisture sensor and printing its value:

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

void loop() {
  int moisture = analogRead(0);
  Serial.print(moisture);
  delay(1000);
}

medium

A. Serial.print() should be Serial.println() to add a new line.

B. Serial.begin() must be called inside loop().

C. delay() cannot be used inside loop().

D. analogRead() should use A0 instead of 0.

Solution

1. Step 1: Check analogRead() argument

   Using analogRead(0) reads digital pin 0, which is incorrect for analog input.

2. Step 2: Use A0 for analog pin 0

   The correct syntax is analogRead(A0) to read analog pin A0.

3. Final Answer:

   analogRead() should use A0 instead of 0. -> Option D

4. Quick Check:

   Use A0 constant for analog pins [OK]

Hint: Use A0, A1, etc. for analogRead() pins [OK]

Common Mistakes:

• Using integer 0 instead of A0 in analogRead()
• Thinking Serial.print() must be println() always
• Believing delay() is not allowed in loop()
• Calling Serial.begin() inside loop()

5.

You want to turn on a water pump when the soil moisture is below 300. Which code snippet correctly implements this using a soil moisture sensor on A0 and a pump connected to digital pin 7?

void setup() {
  Serial.begin(9600);
  pinMode(7, OUTPUT);
}

void loop() {
  int moisture = analogRead(A0);
  if (?) {
    digitalWrite(7, HIGH);
  } else {
    digitalWrite(7, LOW);
  }
  delay(1000);
}

hard

A. moisture < 300

B. moisture > 300

C. moisture == 300

D. moisture != 300

Solution

1. Step 1: Understand the condition for watering

   The pump should turn on when soil is dry, meaning moisture value is less than 300.

2. Step 2: Write the correct if condition

   The condition moisture < 300 triggers the pump ON with digitalWrite(7, HIGH);.

3. Final Answer:

   moisture < 300 -> Option A

4. Quick Check:

   Turn pump ON if moisture below threshold [OK]

Hint: Use if moisture < threshold to activate pump [OK]

Common Mistakes:

• Using > instead of < for dry soil condition
• Checking equality instead of range
• Forgetting to set pinMode for pump pin