Unit 6: Introduction of Arduino and Sensors - Practice Quiz

1 Which statement best describes an analog signal?

2 A basic digital signal commonly uses which two logic levels?

3 Which quantity is most naturally represented by an analog signal?

4 Which device generally produces a digital input when it is simply pressed or released?

5 Which pins on an Arduino Uno are commonly used to read analog sensor values?

6 What is the purpose of a GND pin on an Arduino board?

7 What is the main function of the microcontroller on an Arduino board?

8 Which Arduino Uno pins can generally be configured as either inputs or outputs?

9 What does the abbreviation IR stand for?

10 A basic reflective IR sensor detects an object mainly by sensing what?

11 Which application commonly uses an IR sensor?

12 What does the abbreviation LDR stand for?

13 What usually happens to the resistance of an LDR when light intensity increases?

14 Which project is a common application of an LDR?

15 Which type of wave is used by an ultrasonic distance sensor?

16 What does an ultrasonic sensor measure to determine the distance of an object?

17 Which formula represents the distance measured using the round-trip time and speed of sound ?

18 Which two environmental quantities can both DHT11 and DHT22 sensors measure?

19 What type of output is provided by a DHT11 sensor?

20 Compared with the DHT11, which sensor generally offers a wider measurement range and better accuracy?

21 An Arduino Uno uses a 10-bit ADC with a reference voltage of . What ADC value is expected for an input of ?

22 A digital input reads LOW below and HIGH above . What is the main problem if the input remains near ?

23 A sensor signal contains frequency components up to . Which sampling rate satisfies the Nyquist criterion?

24 An Arduino PWM pin outputs a pulse train with a 40% duty cycle. What average voltage is obtained after suitable low-pass filtering?

25 On an Arduino Uno, which pins should generally be avoided for an ordinary sensor if USB serial communication is being used?

26 A motor-speed control circuit requires a PWM signal from an Arduino Uno. Which selected pin is suitable?

27 A sensor provides a continuously varying output voltage between and . Where should its output be connected on an Arduino Uno for measurement?

28 Two modules must communicate with an Arduino Uno through the I2C bus. Which pair of Uno pins carries the I2C signals?

29 An LED is connected from Arduino pin 8 to GND through a resistor. Which configuration and output combination turns it on?

30 An IR obstacle sensor detects a black surface less reliably than a white surface at the same distance. What is the most likely reason?

31 An active-LOW IR sensor module gives LOW when an obstacle is present. Which program condition should trigger an alarm?

32 An IR obstacle detector produces false detections in direct sunlight. Which explanation best accounts for this behavior?

33 An LDR is connected to and a fixed resistor is connected from the output node to GND. What happens to the output voltage when light intensity increases?

34 An LDR of is connected to , and a resistor connects the output node to GND. What is the output voltage?

35 A streetlight controlled by an LDR switches rapidly on and off near twilight. Which modification best reduces this behavior?

36 An ultrasonic sensor measures a round-trip echo time of . Taking the speed of sound as , how far away is the object?

37 Why is the measured echo travel distance divided by two when calculating object distance?

38 An ultrasonic sensor gives unstable readings from a smooth wall placed at a steep angle. What is the most likely cause?

39 A project must measure temperatures below with better resolution. Which sensor is generally more suitable?

40 A DHT sensor occasionally returns invalid checksum errors when read in a fast loop. Which change is most appropriate?

41 An Arduino Uno reads an analog sensor using its 10-bit ADC with a 5 V reference. If the input is 3.72 V, what digital value is expected most closely, assuming ideal conversion?

42 A slowly varying analog signal is sampled at 800 Hz. The signal contains a desired component at 120 Hz and an unwanted component at 510 Hz. What will most likely be observed after sampling if no anti-aliasing filter is used?

43 An Arduino digital input has a HIGH threshold of approximately 3 V and a LOW threshold of approximately 1.5 V. A slowly changing sensor output remains at 2.2 V for several seconds. How should this input state be classified?

44 A 10-bit ADC uses a 2.56 V reference. What is the smallest ideal input-voltage change that can produce a one-count change in the conversion result?

45 On an Arduino Uno, a sketch uses analogWrite(9, 128) to control LED brightness. Which statement best describes the generated signal?

46 An Arduino Uno circuit requires SPI communication with a peripheral. Which pin assignment is correct for the hardware SPI interface?

47 A circuit drives an external 5 V signal into Arduino Uno pin 2 and also connects the signal source ground to Arduino GND. Which change is most important when the external signal may exceed 5 V?

48 A pushbutton is connected between Arduino Uno pin 7 and ground, and INPUT_PULLUP is configured. What reading pattern should the program interpret as a pressed button?

49 An obstacle-detection IR module gives a LOW output when it detects a nearby object. The output remains LOW when a highly reflective white surface is moved farther away. Which explanation is most plausible?

50 An IR proximity sensor works reliably indoors but frequently detects obstacles in direct sunlight. What is the best engineering remedy?

51 An IR reflective module has an adjustable threshold and produces unstable output near a boundary. Which change most directly reduces rapid switching caused by small signal fluctuations?

52 An LDR has a resistance of 10 kΩ in darkness and 1 kΩ in bright light. It is connected in a divider with a fixed 10 kΩ resistor from 5 V to ground, with the output taken at the junction. What happens to the output voltage in bright light?

53 An LDR divider is connected to an Arduino analog input. The reading changes significantly when a motor starts, even though illumination is constant. Which cause is most likely?

54 Two identical LDR dividers are used to detect left-right light imbalance. To make the differential reading less sensitive to changes in overall illumination, which approach is most appropriate?

55 An ultrasonic sensor measures the round-trip echo time as 8.0 ms. Taking the speed of sound as 343 m/s, what is the approximate target distance?

56 An HC-SR04-style sensor is mounted 1.2 m above a flat floor and points vertically downward. With the speed of sound at 343 m/s, what echo duration should be expected approximately?

57 Two ultrasonic sensors are installed close together and triggered almost simultaneously. Their readings become erratic. What is the most likely cause and remedy?

58 An ultrasonic sensor reports an unexpectedly long distance when aimed at a smooth, angled glass surface. Which explanation is most accurate?

59 A DHT22 is connected using a long cable, and its data line occasionally stays HIGH or returns corrupted readings. Which hardware change is generally most appropriate?

60 A program requests DHT22 data every 20 ms and receives many invalid results. What is the primary reason?