Arduino & IR Sensor MCQs

1. What type of microcontroller is used in the Arduino Uno board?

a) ATmega328P b) ATmega2560 c) PIC16F877A d) ARM Cortex M3

Correct Answer: a) ATmega328P

Explanation:
The Arduino Uno board uses the ATmega328P microcontroller: - 8-bit AVR microcontroller - 32KB flash memory - 2KB SRAM - 1KB EEPROM - 16MHz clock speed Other Arduino boards use different microcontrollers (e.g., ATmega2560 in Mega)

2. How many digital input/output pins does an Arduino Uno have?

a) 14 b) 16 c) 20 d) 12

Correct Answer: a) 14

Explanation:
Arduino Uno digital I/O pins: - Total 14 digital pins (numbered 0-13) - All can be used as input or output - Pins 0 and 1 are also used for serial communication (RX/TX) - 6 pins (3,5,6,9,10,11) support PWM output

3. Which pins on the Arduino Uno can be used for Pulse Width Modulation (PWM)?

a) 0-5 b) 3, 5, 6, 9, 10, 11 c) 2, 4, 6, 8, 10, 12 d) 7, 8, 9, 10, 11, 12

Correct Answer: b) 3, 5, 6, 9, 10, 11

Explanation:
PWM pins on Arduino Uno: - 6 pins marked with ~ symbol - Pins 3, 5, 6, 9, 10, 11 - Provide analog-like output using digital pulses - Used for controlling LED brightness, motor speed, etc. - 8-bit resolution (0-255 values)

4. What is the operating voltage of the Arduino Uno board?

a) 12V b) 9V c) 5V d) 3.3V

Correct Answer: c) 5V

Explanation:
Arduino Uno voltage specifications: - Operating voltage: 5V (for logic levels) - Input voltage (recommended): 7-12V - Input voltage (limits): 6-20V - 3.3V pin available but not main operating voltage - 5V regulator provides stable 5V supply

5. Which interface is used for programming an Arduino Uno board?

a) SPI b) UART c) I2C d) USB

Correct Answer: d) USB

Explanation:
Arduino Uno programming: - Typically programmed via USB connection - Uses USB-to-serial converter (ATmega16U2 or CH340) - No external programmer needed - Programs uploaded through Arduino IDE - USB also provides power during development

6. What is the function of the "Vin" pin on the Arduino board?

a) It is used for analog inputs b) It provides 5V output c) It is used for external power input d) It is used for PWM output

Correct Answer: c) It is used for external power input

Explanation:
Vin pin functionality: - Input voltage to the Arduino when not using USB - Connected to the voltage regulator - Accepts 7-12V DC input - Can also be used to measure input voltage - Not regulated - same as power jack input

7. What is the maximum current rating of the Arduino Uno's 5V pin?

a) 200mA b) 500mA c) 800mA d) 1A

Correct Answer: b) 500mA

Explanation:
5V pin current limitations: - Total current from all I/O pins: 200mA - 5V pin can provide ~500mA (shared with USB) - Exceeding may damage regulator or USB port - For higher current needs, use external power - 3.3V pin limited to 150mA

8. What is the function of the AREF pin in Arduino?

a) It provides analog reference voltage b) It supplies power to external sensors c) It is used for reset operations d) It is used for digital communication

Correct Answer: a) It provides analog reference voltage

Explanation:
AREF pin details: - Analog Reference pin - Used to set external reference voltage for ADC - Default reference is 5V (or 3.3V on 3.3V boards) - Can use analogReference() function to configure - Allows for more precise analog measurements

9. What type of communication is used by the Serial Monitor in Arduino IDE?

a) SPI b) I2C c) UART d) CAN

Correct Answer: c) UART

Explanation:
Serial Monitor communication: - Uses UART (Universal Asynchronous Receiver/Transmitter) - Default baud rate: 9600 - Uses USB-to-serial conversion - Pins 0 (RX) and 1 (TX) handle the communication - Useful for debugging and data monitoring

10. What is the function of the RESET pin in Arduino?

a) Stops power supply b) Resets the microcontroller c) Enables bootloader d) Disables serial communication

Correct Answer: b) Resets the microcontroller

Explanation:
RESET pin functionality: - Active-low reset (bring to GND to reset) - Restarts the program from beginning - Similar to pressing the reset button - Can be triggered externally - Does not erase program memory

11. What is the working principle of an IR sensor?

a) It detects visible light b) It detects sound waves c) It detects infrared radiation d) It detects pressure variations

Correct Answer: c) It detects infrared radiation

Explanation:
IR sensor working principle: - Detects infrared radiation (700nm-1mm wavelength) - Invisible to human eye - All objects emit some IR radiation - IR receivers detect reflected or emitted IR - Used in proximity sensing, object detection

12. What is the function of the IR LED in an IR sensor module?

a) It receives infrared signals b) It transmits infrared signals c) It amplifies the received signals d) It converts light into electrical signals

Correct Answer: b) It transmits infrared signals

Explanation:
IR LED function: - Emits infrared light when current flows - Typical wavelength: 940nm - Acts as transmitter in IR sensor pair - Requires current-limiting resistor - Modulation helps avoid interference

13. What is the typical wavelength range of infrared radiation used in IR sensors?

a) 100 nm – 400 nm b) 400 nm – 700 nm c) 700 nm – 1 mm d) 1 mm – 10 mm

Correct Answer: c) 700 nm – 1 mm

Explanation:
IR wavelength spectrum: - Near IR: 700nm-1400nm (most common for sensors) - Mid IR: 1400nm-3000nm - Far IR: 3000nm-1mm (thermal imaging) - Visible light: 400-700nm - Most IR sensors use 850nm or 940nm LEDs

14. Which type of photodiode is used in IR sensors?

a) Visible light photodiode b) UV photodiode c) IR-sensitive photodiode d) X-ray photodiode

Correct Answer: c) IR-sensitive photodiode

Explanation:
IR photodiode characteristics: - Specifically sensitive to infrared wavelengths - Acts as receiver in IR sensor pair - Generates current when exposed to IR - Often paired with IR LED - May include optical filter to block visible light

15. What is the function of an op-amp in an IR sensor circuit?

a) Generates infrared waves b) Amplifies the received signal c) Converts IR signals into digital output d) Converts voltage to current

Correct Answer: b) Amplifies the received signal

Explanation:
Op-amp in IR circuits: - Amplifies weak signal from photodiode - Often configured as comparator - Helps distinguish between presence/absence of IR - Can adjust sensitivity via potentiometer - Provides clean digital output

16. How is an obstacle detected using an IR sensor?

a) By measuring changes in temperature b) By detecting light reflection c) By detecting sound waves d) By using a magnetic field

Correct Answer: b) By detecting light reflection

Explanation:
IR obstacle detection: 1. IR LED emits infrared light 2. If obstacle present, IR reflects back 3. Photodiode detects reflected IR 4. Circuit processes the signal 5. Output indicates obstacle presence Detection depends on reflectivity of surface

17. Which of the following is NOT a common application of IR sensors?

a) Motion detection b) Line following robots c) Temperature sensing d) Remote control operation

Correct Answer: c) Temperature sensing

Explanation:
IR sensor applications: - Motion detection (PIR sensors) - Line following robots (reflectivity) - Remote controls (IR communication) - Object detection - NOT typically used for temperature sensing (requires specialized IR thermometers)

18. What type of IR sensor is used in TV remote controls?

a) Active IR sensor b) Passive IR sensor c) Reflective IR sensor d) Ultrasonic IR sensor

Correct Answer: a) Active IR sensor

Explanation:
TV remote IR system: - Active IR: Has transmitter (LED) and receiver - Remote contains IR LED transmitter - TV has IR receiver - Uses modulated IR signals (38kHz typical) - Different codes for different buttons

19. What happens when an obstacle is detected by an IR sensor in a line-following robot?

a) The robot stops b) The IR sensor sends a signal to the microcontroller c) The IR LED turns off d) The robot moves backward

Correct Answer: b) The IR sensor sends a signal to the microcontroller

Explanation:
Line follower operation: 1. IR sensor detects line (or obstacle) 2. Output signal changes state 3. Microcontroller reads this signal 4. Program decides appropriate action 5. Motors are controlled accordingly The sensor itself doesn't control the robot

20. What can affect the performance of an IR sensor?

a) Ambient temperature b) Sunlight and bright lights c) Distance of the object d) All of the above

Correct Answer: d) All of the above

Explanation:
Factors affecting IR sensors: - Ambient IR sources (sunlight, lamps) - Temperature affects component performance - Distance to object (signal strength) - Surface reflectivity - Interference from other IR sources - Sensor alignment and angle

About Arduino and IR Sensors

Basic Arduino Questions

Pin Configuration and Description

IR Sensor (Infrared Sensor)

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