Reducing power consumption tips in Arduino - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to put the Arduino into sleep mode.

Arduino

#include <avr/sleep.h>

void setup() {
  Serial.begin(9600);
  set_sleep_mode([1]);
  sleep_enable();
  sleep_cpu();
}

void loop() {
  // Empty loop
}

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

ASLEEP_MODE_POWER_DOWN

BSLEEP_MODE_ADC

CSLEEP_MODE_IDLE

DSLEEP_MODE_STANDBY

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a sleep mode that does not reduce power significantly.

The SLEEP_MODE_POWER_DOWN mode puts the Arduino into the lowest power state, reducing power consumption significantly.

2fill in blank

medium

Complete the code to disable the ADC to save power.

Arduino

void setup() {
  ADCSRA [1] 0;
}

void loop() {
  // Main code
}

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

A|=

B=

C^=

D&=

Attempts:

3 left

💡 Hint

Common Mistakes

Using OR or AND operators which do not clear all bits properly.

Using = 0 disables all bits in the ADCSRA register, turning off the ADC to save power.

3fill in blank

hard

Fix the error in the code to turn off the built-in LED to save power.

Arduino

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, [1]);
}

void loop() {
  // Empty loop
}

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

AINPUT

BHIGH

CLOW

DOUTPUT

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the pin HIGH which keeps the LED on.

Setting the LED pin to LOW turns off the LED, reducing power consumption.

4fill in blank

hard

Fill both blanks to create a dictionary of sensor readings only if the reading is above 100.

Arduino

int readings[] = {120, 90, 150, 80};

void setup() {
  Serial.begin(9600);
  for (int i = 0; i < 4; i++) {
    if (readings[i] [1] 100) {
      Serial.println(readings[i] [2] 2);
    }
  }
}

void loop() {}

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

A>

B*

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using less than operator which filters wrong values.

Using addition instead of multiplication.

The condition readings[i] > 100 filters readings above 100. Multiplying by 2 doubles the value before printing.

5fill in blank

hard

Fill all three blanks to create a map of sensor names to values only if the value is positive.

Arduino

String sensors[] = {"temp", "light", "sound"};
int values[] = {25, -5, 10};

void setup() {
  Serial.begin(9600);
  for (int i = 0; i < 3; i++) {
    if (values[i] [3] 0) {
      Serial.print(sensors[i].[1]());
      Serial.print(": ");
      Serial.println(values[i] [2] 1);
    }
  }
}

void loop() {}

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

AtoUpperCase

B*

C>

DtoLowerCase

Attempts:

3 left

💡 Hint

Common Mistakes

Using toUpperCase instead of toLowerCase.

Using addition instead of multiplication.

The condition values[i] > 0 filters positive values. Using toLowerCase() converts sensor names to lowercase. Multiplying by 1 keeps the value unchanged.

Practice

1. Which of the following is a common method to reduce power consumption on an Arduino?

easy

A. Keeping all hardware modules enabled at all times

B. Increasing the clock speed to maximum

C. Using sleep modes to pause the CPU when idle

D. Running the Arduino without any power source

Solution

1. Step 1: Understand power saving basics

   Sleep modes reduce power by pausing the CPU when it is not needed.

2. Step 2: Evaluate other options

   Increasing clock speed or keeping hardware enabled increases power use; running without power is impossible.

3. Final Answer:

   Using sleep modes to pause the CPU when idle -> Option C

4. Quick Check:

   Sleep modes = power saving [OK]

Hint: Sleep modes save power by pausing CPU [OK]

Common Mistakes:

• Thinking higher clock speed saves power
• Believing all hardware should stay enabled
• Ignoring the need for a power source

2. Which Arduino function is used to put the microcontroller into sleep mode?

easy

A. pinMode()

B. digitalWrite()

C. delay()

D. sleep_mode()

Solution

1. Step 1: Identify sleep mode function

   The function sleep_mode() is used to put the microcontroller into sleep mode.

2. Step 2: Check other functions

   digitalWrite() controls pins, delay() pauses code, pinMode() sets pin mode; none put it into sleep.

3. Final Answer:

   sleep_mode() -> Option D

4. Quick Check:

   sleep_mode() = enter sleep [OK]

Hint: sleep_mode() puts Arduino into sleep [OK]

Common Mistakes:

• Confusing delay() with sleep functions
• Using digitalWrite() to control power
• Not knowing pinMode() sets pin direction

3. What will be the effect of this code snippet on power consumption?

void setup() {
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);
  // No sleep mode used
}
void loop() {
  // Empty loop
}

medium

A. Power consumption remains high because no sleep mode is used

B. Power consumption is reduced by turning off pin 13

C. Power consumption is zero because loop is empty

D. Pin 13 will blink, increasing power use

Solution

1. Step 1: Analyze pin state

   Pin 13 is set to LOW, so it does not consume extra power from that pin.

2. Step 2: Check for sleep mode

   No sleep mode is used, so the CPU runs continuously, consuming normal power.

3. Final Answer:

   Power consumption remains high because no sleep mode is used -> Option A

4. Quick Check:

   No sleep mode = normal power use [OK]

Hint: No sleep mode means no power saving [OK]

Common Mistakes:

• Assuming LOW pin means zero power
• Thinking empty loop stops CPU
• Believing pin 13 blinks automatically

4. Identify the error in this code that tries to reduce power consumption:

void setup() {
  sleep_enable();
  sleep_mode();
  sleep_disable();
}
void loop() {
  // do nothing
}

medium

A. The code does not put the CPU to sleep properly because it lacks an interrupt to wake up

B. sleep_disable() should be called before sleep_mode()

C. sleep_mode() is called without enabling sleep first

D. pinMode() is missing for sleep functions

Solution

1. Step 1: Review sleep sequence

   sleep_enable() and sleep_mode() are correctly called to enter sleep.

2. Step 2: Check wake-up mechanism

   Without an interrupt or event to wake the CPU, it may stay asleep indefinitely or behave unexpectedly.

3. Final Answer:

   The code does not put the CPU to sleep properly because it lacks an interrupt to wake up -> Option A

4. Quick Check:

   Sleep needs wake interrupt [OK]

Hint: Sleep requires wake interrupt to resume [OK]

Common Mistakes:

• Thinking sleep_disable() must come before sleep_mode()
• Ignoring the need for wake interrupts
• Assuming pinMode() affects sleep functions

5. You want to reduce power consumption by disabling unused hardware modules on your Arduino. Which approach is best?

hard

A. Use digitalWrite() to disable hardware modules

B. Use power_adc_disable() to turn off the analog-to-digital converter when not needed

C. Keep all modules enabled to avoid errors

D. Increase the clock speed to finish tasks faster

Solution

1. Step 1: Identify hardware disabling functions

   Functions like power_adc_disable() turn off specific hardware modules to save power.

2. Step 2: Evaluate other options

   Increasing clock speed uses more power; keeping all modules enabled wastes energy; digitalWrite() controls pins, not modules.

3. Final Answer:

   Use power_adc_disable() to turn off the analog-to-digital converter when not needed -> Option B

4. Quick Check:

   Disable unused hardware = power_adc_disable() [OK]

Hint: Disable unused hardware with power_*_disable() [OK]

Common Mistakes:

• Thinking digitalWrite() disables hardware modules
• Believing higher clock speed saves power
• Not disabling unused modules wastes battery