Multiple sensor fusion in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of fused sensor data averaging

Given two sensors providing integer readings, what is the output of the fused average printed by the Arduino code below?

Arduino

int sensor1 = 30;
int sensor2 = 50;
int fusedValue = (sensor1 + sensor2) / 2;
void setup() {
  Serial.begin(9600);
  Serial.println(fusedValue);
}
void loop() {}

A 50

B 80

C 30

D 40

💡 Hint

Think about how averaging two numbers works.

The code adds sensor1 and sensor2 (30 + 50 = 80) and divides by 2, resulting in 40.

❓ Predict Output

intermediate

Output of weighted sensor fusion

What value does the Arduino print when fusing two sensor readings with weights 0.7 and 0.3 respectively?

Arduino

float sensor1 = 20.0;
float sensor2 = 40.0;
float fusedValue = sensor1 * 0.7 + sensor2 * 0.3;
void setup() {
  Serial.begin(9600);
  Serial.println(fusedValue);
}
void loop() {}

A 26.0

B 30.0

C 28.0

D 32.0

💡 Hint

Multiply each sensor by its weight and add the results.

20.0 * 0.7 = 14.0, 40.0 * 0.3 = 12.0, 14.0 + 12.0 = 26.0.

🔧 Debug

advanced

Identify the error in sensor fusion code

What value does the following Arduino code print?

Arduino

int sensor1 = 10;
int sensor2 = 20;
int fusedValue = sensor1 + sensor2 / 2;
void setup() {
  Serial.begin(9600);
  Serial.println(fusedValue);
}
void loop() {}

A Prints 15

B Prints 30

C Prints 20

D Prints 25

💡 Hint

Remember operator precedence in arithmetic expressions.

Division happens before addition, so sensor2/2 = 10, then add sensor1 (10 + 10 = 20).

❓ Predict Output

advanced

Output of sensor fusion with conditional logic

What is the output of the Arduino code that fuses two sensor values but uses a condition to select the higher value?

Arduino

int sensor1 = 45;
int sensor2 = 55;
int fusedValue;
void setup() {
  Serial.begin(9600);
  if(sensor1 > sensor2) {
    fusedValue = sensor1;
  } else {
    fusedValue = sensor2;
  }
  Serial.println(fusedValue);
}
void loop() {}

A 55

B 45

C 100

D 0

💡 Hint

Check which sensor value is bigger.

Since 55 is greater than 45, fusedValue is set to 55.

🧠 Conceptual

expert

Number of fused data points after combining three sensors

If you fuse data from three sensors each providing 5 readings, how many total fused data points do you get if you combine readings pairwise and then fuse those results?

A 25

B 5

C 15

D 10

💡 Hint

Think about how many readings are combined at each step and if the number changes.

Pairwise fusion combines readings at the same index, so total fused points remain 5.

Practice

1. What is the main purpose of multiple sensor fusion in Arduino projects?

easy

A. To make sensors work independently without Arduino

B. To combine data from different sensors for better accuracy

C. To reduce the power consumption of sensors

D. To increase the number of sensors connected to Arduino

Solution

1. Step 1: Understand sensor fusion concept

   Multiple sensor fusion means combining data from different sensors to get more reliable results.

2. Step 2: Identify the main goal

   The goal is to improve accuracy by using data from multiple sources.

3. Final Answer:

   To combine data from different sensors for better accuracy -> Option B

4. Quick Check:

   Sensor fusion = combine data for accuracy [OK]

Hint: Sensor fusion means combining sensor data for accuracy [OK]

Common Mistakes:

• Thinking sensor fusion just adds more sensors
• Confusing power saving with fusion
• Assuming sensors work independently

2. Which Arduino function is commonly used to read analog sensor values for fusion?

easy

A. analogRead()

B. digitalRead()

C. sensorRead()

D. readAnalog()

Solution

1. Step 1: Recall Arduino sensor reading functions

   Arduino uses digitalRead() for digital sensors and analogRead() for analog sensors.

2. Step 2: Identify correct function for analog sensors

   analogRead() reads analog sensor values needed for fusion.

3. Final Answer:

   analogRead() -> Option A

4. Quick Check:

   Analog sensor read = analogRead() [OK]

Hint: Use analogRead() for analog sensors in Arduino [OK]

Common Mistakes:

• Using digitalRead() for analog sensors
• Choosing non-existent functions like sensorRead()
• Confusing function names

3. What will be the output of this Arduino code snippet for sensor fusion?

int sensor1 = 400;
int sensor2 = 600;
int fusedValue = (sensor1 + sensor2) / 2;
Serial.println(fusedValue);

medium

A. 500

B. 400

C. 1000

D. 600

Solution

1. Step 1: Calculate sum of sensor values

   sensor1 + sensor2 = 400 + 600 = 1000

2. Step 2: Calculate average for fusion

   Average = 1000 / 2 = 500

3. Final Answer:

   500 -> Option A

4. Quick Check:

   (400+600)/2 = 500 [OK]

Hint: Average sensor values by adding and dividing by count [OK]

Common Mistakes:

• Adding but forgetting to divide
• Dividing by wrong number
• Printing wrong variable

4. Identify the error in this Arduino code for fusing two sensor readings:

int sensor1 = analogRead(A0);
int sensor2 = analogRead(A1);
int fusedValue = sensor1 + sensor2 / 2;
Serial.println(fusedValue);

medium

A. analogRead() cannot be used on pins A0 and A1

B. Serial.println() cannot print integers

C. fusedValue should be a float, not int

D. The division operator has higher precedence, so sensor2 is divided by 2 before adding sensor1

Solution

1. Step 1: Analyze operator precedence in expression

   Division (/) has higher precedence than addition (+), so sensor2 / 2 happens first.

2. Step 2: Understand the effect on fusedValue

   Expression equals sensor1 + (sensor2 / 2), not (sensor1 + sensor2) / 2 as intended.

3. Final Answer:

   The division operator has higher precedence, so sensor2 is divided by 2 before adding sensor1 -> Option D

4. Quick Check:

   Operator precedence causes wrong fusion calculation [OK]

Hint: Use parentheses to control math order in fusion calculations [OK]

Common Mistakes:

• Ignoring operator precedence
• Thinking analogRead() is invalid on A0/A1
• Believing Serial.println() can't print ints

5. You have three sensors giving values: 300, 450, and 500. To fuse these readings and reduce noise, which Arduino code correctly calculates the average value?

hard

A. int fused = (300 + 450 + 500) * 3;

B. int fused = 300 + 450 + 500 / 3;

C. int fused = (300 + 450 + 500) / 3;

D. int fused = (300 + 450 + 500) / 2;

Solution

1. Step 1: Understand correct averaging formula

   Average = sum of values divided by number of values, so (300+450+500)/3.

2. Step 2: Check each option's calculation

   int fused = (300 + 450 + 500) / 3; correctly sums all and divides by 3. int fused = 300 + 450 + 500 / 3; divides only 500 by 3, wrong order. int fused = (300 + 450 + 500) * 3; multiplies sum by 3, wrong. int fused = (300 + 450 + 500) / 2; divides by 2, wrong count.

3. Final Answer:

   int fused = (300 + 450 + 500) / 3; -> Option C

4. Quick Check:

   Average = sum/3 = correct fusion [OK]

Hint: Sum all sensor values, then divide by count with parentheses [OK]

Common Mistakes:

• Missing parentheses causing wrong math order
• Dividing only last value
• Multiplying instead of dividing