Soil moisture sensor in Arduino - Time & Space Complexity

Time Complexity: Soil moisture sensor

O(n)

Understanding Time Complexity

When working with a soil moisture sensor on Arduino, it is important to understand how the program's running time changes as it reads sensor data repeatedly.

We want to know how the time to complete the program grows as the number of sensor readings increases.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

const int sensorPin = A0;
int sensorValue;

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

void loop() {
  sensorValue = analogRead(sensorPin);
  Serial.println(sensorValue);
  delay(1000);
}
    

This code reads the soil moisture sensor value once every second and prints it to the serial monitor.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The loop() function runs repeatedly, reading the sensor and printing the value.
• How many times: It runs indefinitely, once every second.

How Execution Grows With Input

Each sensor reading and print takes roughly the same time, so the total time grows directly with the number of readings.

Input Size (n readings)	Approx. Operations
10	10 sensor reads and prints
100	100 sensor reads and prints
1000	1000 sensor reads and prints

Pattern observation: The operations increase one-to-one with the number of readings.

Final Time Complexity

Time Complexity: O(n)

This means the time to run grows directly in proportion to how many times the sensor is read.

Common Mistake

[X] Wrong: "The sensor reading happens instantly and does not affect time growth."

[OK] Correct: Each sensor read and print takes time, so more readings mean more total time.

Interview Connect

Understanding how repeated sensor readings affect program time helps you explain how embedded systems handle real-time data efficiently.

Self-Check

"What if we added a nested loop to read multiple sensors each cycle? How would the time complexity change?"