Unit 3: Output devices with NodeMCU - Practice Quiz

1 What is the main purpose of an LCD connected to a NodeMCU?

2 What does LCD stand for?

3 Which communication interface commonly reduces the number of NodeMCU pins required by an LCD?

4 Which two signal lines are used for I2C communication with an LCD?

5 What is the function of the contrast control on a character LCD?

6 What does a 16x2 LCD provide?

7 Why must the GND pins of the NodeMCU and LCD be connected together?

8 How many main LED segments are used to form digits in a seven-segment display?

9 What is a seven-segment display mainly used to show?

10 Why is a resistor connected in series with each segment of a seven-segment display?

11 In a common-cathode seven-segment display, where are the common terminals normally connected?

12 In a common-anode seven-segment display, where are the common terminals normally connected?

13 Which NodeMCU pin mode is normally used to control a seven-segment display segment?

14 What is the optional eighth LED on many seven-segment displays used for?

15 Why should a DC motor not usually be powered directly from a NodeMCU GPIO pin?

16 Which device can act as an electronic switch when controlling a DC motor from a NodeMCU?

17 What is the purpose of a flyback diode connected across a DC motor?

18 Which technique is commonly used to control the speed of a DC motor?

19 Which circuit is commonly used to control the direction of a DC motor?

20 What normally happens when the polarity applied to a simple DC motor is reversed?

21 A 16×2 LCD is connected to a NodeMCU through an I2C module. Which pair of signals is normally required for communication?

22 What is the main advantage of using an I2C adapter with a character LCD and NodeMCU?

23 An LCD displays dark blocks but no characters after power is applied. Which adjustment is most likely to solve the problem?

24 A NodeMCU program initializes an LCD at address 0x27, but the display remains blank. What should be checked first?

25 Why should a common ground be connected between the NodeMCU and an externally powered LCD module?

26 A sensor value on an LCD changes rapidly and becomes difficult to read. Which software approach is most suitable?

27 A 16×2 LCD is used to display a value that sometimes has fewer digits than the previous value. Why can leftover characters appear?

28 For a common-cathode seven-segment display, how is a segment normally turned on?

29 How does the segment control logic differ for a common-anode seven-segment display compared with a common-cathode display?

30 Why is a separate resistor commonly connected in series with each seven-segment LED segment?

31 A digit appears incorrectly on a seven-segment display even though the program logic is correct. Which issue is most likely?

32 A seven-segment display must show digits from 0 to 9 using seven GPIO pins. What should the program generally do for each new digit?

33 Why can directly driving many seven-segment segments from NodeMCU pins create a hardware concern?

34 A multiplexed two-digit seven-segment display uses shared segment lines. What technique allows both digits to appear continuously lit?

35 Why should a DC motor generally not be connected directly to a NodeMCU GPIO pin?

36 Which component is most suitable for controlling a DC motor's direction and speed with a NodeMCU?

37 What is the purpose of a flyback diode across a brushed DC motor when a transistor is used as the switching device?

38 A motor driver receives a PWM signal with a duty cycle of approximately . What is the expected effect compared with a duty cycle, assuming the same supply?

39 When a NodeMCU controls a motor driver powered by a separate battery, which connection is normally necessary for reliable control signals?

40 An H-bridge motor driver has input pins IN1 and IN2. Which input combination commonly commands the motor to stop using active braking or driver logic?

41 A 16x2 LCD with an I2C backpack is connected to a NodeMCU. The display works intermittently when a motor on the same supply starts. Which hardware change most directly addresses the likely communication fault?

42 An I2C LCD backpack is powered from 5 V, while its SDA and SCL pull-up resistors also reach 5 V. Why is this connection unsafe for a NodeMCU configured for 3.3 V GPIO operation?

43 A NodeMCU LCD program hangs inside lcd.init() after wiring SDA and SCL to GPIO4 and GPIO5. The LCD has power and a visible backlight. Which diagnosis is most appropriate before changing the software library?

44 A design must update an I2C LCD every 10 ms while also servicing time-critical sensor interrupts. Which architecture best reduces avoidable timing disruption?

45 An LCD displays correct text after reset, but later shows duplicated or shifted characters when strings of different lengths are written to the same row. What is the most reliable software correction?

46 A NodeMCU uses GPIO0 as an LCD control line. The board sometimes enters programming mode instead of booting normally. Which explanation best accounts for this behavior?

47 The LCD is powered from a separate 5 V adapter, and the NodeMCU is powered by USB. Characters are corrupted even though both devices measure correct local voltages. What connection is essential?

48 A common-cathode seven-segment display is driven directly from NodeMCU GPIO pins. One segment draws 18 mA, but the design must satisfy a 12 mA maximum per GPIO. Which change preserves the displayed pattern while meeting the limit?

49 A common-anode display is connected to a NodeMCU through low-side transistor drivers for its segment lines. Which output behavior should represent an illuminated segment?

50 During multiplexing of a four-digit common-cathode display, faint segments from the previous digit appear on the next digit. Which sequence most effectively prevents ghosting?

51 Each segment is driven at 12 mA while active, and a multiplexed display has a duty cycle of . Ignoring nonlinear LED effects, what is the approximate average current per continuously lit segment?

52 A two-digit multiplexed display shares seven segment lines, but the NodeMCU has only one GPIO available for both digit selection and segment data timing. Which solution is most appropriate?

53 A display driver uses an 8-bit lookup table for digits, but every digit appears horizontally mirrored or incorrectly segmented. The wiring order is known to be reversed relative to the table. What is the cleanest correction?

54 A multiplexed display flickers noticeably even though its scan rate is 200 Hz per complete frame. The firmware spends 8 ms blocking in another task between digit updates. What is the strongest fix?

55 Why must a DC motor generally not be connected directly between a NodeMCU GPIO pin and ground?

56 A low-side N-channel MOSFET controls a motor, but the motor resets the NodeMCU whenever it turns off. The motor has no suppression component. Which addition is most directly required?

57 A motor driver accepts a 3.3 V logic signal, but the motor supply is 12 V and shares ground with the NodeMCU. Which statement is correct?

58 A NodeMCU controls motor speed with PWM, but the motor stalls at low duty cycles and draws large current pulses. Which change is most likely to improve startup behavior?

59 An H-bridge is used to reverse a motor. The firmware changes one bridge input from high to low while changing the other from low to high at nearly the same instant. What protection is most important?

60 A motor supply is adequate at no load but its voltage collapses during acceleration, causing the NodeMCU to reboot. Which design response best addresses the system-level cause?