Practicals

Question 1

What is an ESP32?

Answer 1

A System on Chip (SoC) Microcontroller with integrated Wi-Fi and Bluetooth

Question 2

What are the capabilities of an ESP32?

Answer 2

Able to interface with other systems to provide Wi-Fi and Bluetooth functionality through its SPI, I2C or UART interfaces

Question 3

Explain how a PWM signal from a microcontroller can be used to control the speed of a motor

Answer 3

• The width of digital pulses is adjusted to generated different average dc voltages
• These dc voltages are then passed through the motor with less voltage meaning slower speeds and vice versa

Question 4

Explain how an encoder could be used to measure the speed of a motor

Answer 4

• Every second, record the new encoder count and store it
• Subtract the previous encoder count from the new encoder count
• Calculate RPM by multiplying encoder count by 60 then dividing by the pulses per rotation
• Reset the encoder count to 0

Question 5

Explain how you could use a pair of motor encoders to travel in a straight line

Answer 5

• While moving, record the encoder counts
• If the left encoder count is greater than the right, decrease the left motor speed and increase the right motor speed and vice versa

Question 6

What are the benefits of using an encoder instead of a delay to stop the car after a specified distance?

Answer 6

• The distance needed to be travelled will always be a constant based on the code
• If delay is used, the speed is now a factor variable which can be affected by voltage fluctuations to the motors
• An encoder gives better control over speed

Question 7

How do you safely power an LED?

Answer 7

• By adding a resistor into the circuit
• Resistance value needed can be calculated by equation R = V / I , where V is Supply voltage - LED voltage

Question 8

Describe the purpose of a pull-up resistor

Answer 8

To ensure that a pin always has a defined logical level under all conditions, stopping the input from being in an undefined state

Question 9

What is a MOSFET?

Answer 9

A transistor where the gate voltage manipulates the conductivity between the source and drain regions

Question 10

Explain the operation of the bi-directional voltage level shifter

Answer 10

To shift the voltage of a signal either up to 5V or down to 3.3V

Question 11

What is the purpose of the ‘L298N’ motor driver chip?

Answer 11

To control the speed and direction of the two DC motors

Question 12

What is the purpose of the ‘SPX29300T-L-5-0/TR’ regulator on the rear of the EEEBot mainboard?

Answer 12

To create and maintain a fixed 5V output voltage, despite changes to the input voltage or load condition

Question 13

What is the purpose of the two fuses and MOSFET on the EEEBot mainboard?

Answer 13

For temperature protection to prevent the MOSFET from being damaged

Question 14

On the EEEBot mainboard, why is 5V from the regulator preferable to using voltage pins from the ESP32?

Answer 14

• As a voltage regulator creates and maintains a fixed 5V output voltage, despite the changes to the input voltage or load condition
• Whereas the voltage using voltage pins could cause voltages on the EEEBot to fluctuate and may cause damages to the chip on the ESP32

Question 15

Explain how I2C works and why it is needed

Answer 15

• Communication takes place between a master and one or more slave devices
• The serial computer bus requires two data lines, SDA and SCL

Question 16

What are the benefits of I2C over UART

Answer 16

• I2C has a faster data transmission rate than UART
• I2C has multi-device support, unlike UART
• I2C has an unlimited data size, whereas UART is limited to 9 bits only

Question 17

What is the difference between accuracy and precision?

Answer 17

• Accuracy is how close the calculated values are to the true value
• Precision is how close the calculated values are to each other

Question 18

What is the operating principle of an HC-SR04 sensor?

Answer 18

Infers distance to an object by measuring the time taken for 40kHz sound wave from the trigger pin to travel from a transmitter to the object and then back to a receiver connected to the echo pin

Question 19

What is an MPU-6050 ?

Answer 19

An inertial measurement unit (IMU) capable of measuring rotation in a number of motion tracking axes

Question 20

What can an MPU-6050 specifically measure?

Answer 20

• Angular velocity
• Acceleration

Question 21

What is ‘MQTT’?

Answer 21

A messaging protocol to exchange data between multiple devices

Question 22

How does ‘MQTT’ work?

Answer 22

• Devices on the network subscribe to topics
• Devices on the network publish messages related to a topic
• Any device subscribe to the topic receives the message