Unit 2: Input devices with NodeMCU - Practice Quiz

1 Which two environmental quantities are measured by a DHT11 sensor?

2 Which DHT11 pin sends sensor readings to the NodeMCU?

3 Which Arduino function is commonly used to start a DHT sensor object?

4 Which function commonly reads relative humidity from a DHT library?

5 What does an ultrasonic sensor commonly measure?

6 Which ultrasonic sensor pin is used to send the sound pulse?

7 Which ultrasonic sensor pin returns a pulse whose duration represents distance?

8 Why is the sound travel distance divided by 2 when calculating object distance?

9 Which NodeMCU pin is typically used to read an analog temperature sensor?

10 Which Arduino function reads a value from an analog temperature sensor?

11 What must usually be done to an analog temperature sensor's ADC reading to obtain temperature?

12 What is a common use of an IR sensor connected to a NodeMCU?

13 Which Arduino function commonly reads the digital output of an IR sensor?

14 How should a NodeMCU pin connected to an IR sensor's digital output normally be configured?

15 Which sensor generally provides better measurement accuracy?

16 Which sensor generally supports a wider temperature measurement range?

17 Which sensor is generally less expensive for basic temperature and humidity projects?

18 What does an LDR sensor detect?

19 How does an LDR's resistance normally change when light intensity increases?

20 Why is an LDR commonly connected in a voltage-divider circuit?

21 A NodeMCU repeatedly receives NaN from dht.readTemperature(). What should the program do before using the returned value?

22 A DHT11 is connected to NodeMCU pin D4. Which initialization is appropriate when using a common DHT sensor library?

23 A program reads a DHT11 every 100 ms and frequently reports invalid values. Which change is most appropriate?

24 A NodeMCU must activate a fan when the DHT11 temperature exceeds , but only when the reading is valid. Which condition is appropriate?

25 An HC-SR04 reports a round-trip echo time of . Using , what distance should the NodeMCU calculate?

26 Which pulse sequence should the NodeMCU apply to the HC-SR04 trigger pin to begin a measurement?

27 Why is a voltage divider commonly placed between the HC-SR04 echo pin and an ESP8266 NodeMCU input?

28 What is the main benefit of adding a timeout to pulseIn(echoPin, HIGH, timeout)?

29 An LM35 produces per degree Celsius. If its measured output is , what temperature should the NodeMCU report?

30 A temperature sensor connected to A0 produces noticeably fluctuating values. Which software technique can provide a steadier displayed temperature?

31 A NodeMCU development board has a documented A0 full-scale voltage of . If analogRead(A0) returns 512 on its 10-bit ADC, what input voltage is approximately present?

32 An active-LOW IR obstacle module outputs LOW when an object is detected. Which condition should control an alarm correctly?

33 An IR obstacle sensor causes an event counter to increase many times while one object remains in front of it. Which program change best counts each new detection once?

34 An IR module's indicator LED responds to an object, but the NodeMCU always reads HIGH. What should be checked first?

35 A greenhouse must measure temperatures below and requires better humidity accuracy. Which sensor is generally more suitable?

36 A program is changed from a DHT11 to a DHT22 while keeping the same data pin. Which code change is normally required?

37 Which design trade-off correctly compares the DHT11 and DHT22?

38 An LDR is connected from 3.3 V to A0, and a fixed resistor is connected from A0 to ground. What generally happens to the ADC reading as light intensity increases?

39 A streetlight controlled by an LDR rapidly switches on and off near the threshold. Which programming approach best prevents this behavior?

40 An LDR divider gives readings of 180 in darkness and 820 in bright light. Which condition appropriately turns an LED on when the environment becomes dark?

41 A NodeMCU reads a DHT11 every 100 ms, but many readings become NaN and the output occasionally freezes. Which change best addresses both problems?

42 A DHT11 data line is connected to a NodeMCU GPIO configured incorrectly as an analog input. The sensor is powered correctly, but readings fail. What is the most appropriate correction?

43 A DHT11 system reports a humidity value of 0 after a communication failure, and the control program turns on a humidifier. Which design prevents this unsafe response?

44 An HC-SR04 is connected to a 3.3 V NodeMCU. Which hardware and software combination is safest for the Echo signal?

45 An ultrasonic measurement returns a pulse duration of 5800 microseconds. Assuming a sound speed of , what distance should be reported?

46 A robot uses two ultrasonic sensors mounted close together and triggers them simultaneously. Measurements are inconsistent even when the robot is stationary. What is the best software correction?

47 A distance function occasionally returns an extremely large value when the target is absent. Which implementation detail most directly prevents this result from being interpreted as a real distance?

48 A temperature sensor is connected to the ESP8266 ADC, whose input range is 0 to 1.0 V, but the sensor can output up to 3.0 V. What is the correct engineering response?

49 For an LM35 connected to a 10-bit ADC with a 1.0 V reference, which equation converts an ADC count to temperature in degrees Celsius, assuming 10 mV per degree Celsius?

50 A temperature control loop switches a heater rapidly when measurements fluctuate by 0.2 degrees Celsius near the setpoint. Which programming strategy best reduces actuator chatter while preserving responsiveness?

51 An IR obstacle module has an active-low digital output. The program currently treats HIGH as obstacle detected, causing the actuator logic to invert. What is the correct fix?

52 An IR sensor output rapidly alternates between detected and clear when an object is near its threshold. Which algorithm is most suitable for stable event detection?

53 An IR receiver is used to decode a remote-control protocol, but decoding fails whenever the main loop performs a long blocking delay. Which redesign is most appropriate?

54 A project requires temperature resolution near 0.1 degrees Celsius and humidity measurements below 20 percent relative humidity. Which sensor choice is technically better?

55 A DHT11 library is used with a DHT22, and the program reports implausible but checksum-valid values. Which cause is most likely?

56 A data logger samples both a DHT11 and a DHT22 every 250 ms. Which statement best predicts the resulting behavior?

57 An LDR and a fixed resistor form a divider connected to A0. The LDR is placed between 3.3 V and the ADC input, and its resistance decreases in bright light. What happens to the ADC reading as light increases?

58 An LDR threshold works in the laboratory but fails after deployment because the NodeMCU supply voltage varies. Which software or hardware improvement gives the most robust light classification?

59 An LDR reading is noisy because the sensor wire runs beside a relay cable. Which combination best improves the measurement without hiding genuine light changes?

60 A NodeMCU LDR application must detect a sudden light interruption while also reporting a stable ambient level. Which architecture best satisfies both requirements?