Output Devices

Group Assignment:

Measure the power consumption of an output device.

Individual Assignment:

Add an output device to a microcontroller board you've designed, and program it to do something

Have you answered these questions?

Linked to the group assignment page ✅

Documented how you determined power consumption of an output device with your group. ✅

Documented what you learned from interfacing output device(s) to microcontroller and controlling the device(s).✅

Linked to the board you made in a previous assignment or documented your design and fabrication process if you made a new board.✅

Explained the programming process/es you used.✅

Explained any problems you encountered and how you fixed them.✅

Included original source code and any new design files.✅

Included a ‘hero shot’ of your board.✅

Group assignment

Measure the power consumption of an output device.

During the group project meeting, I had the opportunity to collaborate with my teammate Jhonathan, who provided a detailed explanation of various measurement concepts. His help was crucial in gaining a better understanding of how a multimeter works and how to interpret its readings. Thanks to his support, I was able to realize that when the voltage is extremely low, the multimeter may not accurately reflect the smallest details, making it difficult to observe small variations. Here is the link to learn more about the group project.

Reflections

By completing this grupal assignment, I have learned many valuable aspects, both technically and practically. One of the most important takeaways was understanding the use and limitations of the tools we are using. Specifically, when measuring the buzzer with a multimeter, I realized how essential it is to interpret data correctly and how small variations, which might seem insignificant at first glance, actually provide crucial information about a device’s functioning.

I was also surprised by the difference between the measurements obtained with the multimeter and what could be achieved with a power meter. This allowed me to reflect on the most appropriate tools for each type of measurement. Understanding that a multimeter can be useful for measuring certain parameters but may not always be precise enough for others made me appreciate the use of specialized devices depending on the context.

The challenge of working remotely with a teammate in another city also taught me the importance of effective communication. Even though we were separated by distance, we were able to coordinate our tasks and discuss our progress thanks to online communication tools. This taught me that remote collaboration is not only possible but can be as productive as in-person work, as long as there is clarity in the goals and task distribution.

Individual assignment

Add an output device to a microcontroller board you've designed, and program it to do something

In week 06, I designed a printed circuit board (PCB), and in week 08, I fabricated a board called "Nave". You can see the complete information here. Electronics Design, Electronics Production.

1. Buzzer

For the output device, one of the components I will use is a buzzer. But what is a buzzer? A buzzer is a device that produces a loud sound when activated and is used in different contexts. On this occasion, I will use it to simulate the song Hedwig's Theme from Harry Potter. To do this, I need to identify the positive and negative terminals to know which pins they should be connected to on an RP2040 microcontroller.

First, I identify the positive terminal on the buzzer, which will be connected to the GND. The negative terminal will be connected to any pin, in this case, I am connecting it to D1, which is pin 27.

After creating the schematic diagram, I will proceed to connect it to the actual PCB.

                                            import time
                                            import machine
                                            
                                            # Note definitions (in Hertz)
                                            NOTE_B0 = 31
                                            NOTE_C1 = 33
                                            NOTE_CS1 = 35
                                            NOTE_D1 = 37
                                            NOTE_DS1 = 39
                                            NOTE_E1 = 41
                                            NOTE_F1 = 44
                                            NOTE_FS1 = 46
                                            NOTE_G1 = 49
                                            NOTE_GS1 = 52
                                            NOTE_A1 = 55
                                            NOTE_AS1 = 58
                                            NOTE_B1 = 62
                                            NOTE_C2 = 65
                                            NOTE_CS2 = 69
                                            NOTE_D2 = 73
                                            NOTE_DS2 = 78
                                            NOTE_E2 = 82
                                            NOTE_F2 = 87
                                            NOTE_FS2 = 93
                                            NOTE_G2 = 98
                                            NOTE_GS2 = 104
                                            NOTE_A2 = 110
                                            NOTE_AS2 = 117
                                            NOTE_B2 = 123
                                            NOTE_C3 = 131
                                            NOTE_CS3 = 139
                                            NOTE_D3 = 147
                                            NOTE_DS3 = 156
                                            NOTE_E3 = 165
                                            NOTE_F3 = 175
                                            NOTE_FS3 = 185
                                            NOTE_G3 = 196
                                            NOTE_GS3 = 208
                                            NOTE_A3 = 220
                                            NOTE_AS3 = 233
                                            NOTE_B3 = 247
                                            NOTE_C4 = 262
                                            NOTE_CS4 = 277
                                            NOTE_D4 = 294
                                            NOTE_DS4 = 311
                                            NOTE_E4 = 330
                                            NOTE_F4 = 349
                                            NOTE_FS4 = 370
                                            NOTE_G4 = 392
                                            NOTE_GS4 = 415
                                            NOTE_A4 = 440
                                            NOTE_AS4 = 466
                                            NOTE_B4 = 494
                                            NOTE_C5 = 523
                                            NOTE_CS5 = 554
                                            NOTE_D5 = 587
                                            NOTE_DS5 = 622
                                            NOTE_E5 = 659
                                            NOTE_F5 = 698
                                            NOTE_FS5 = 740
                                            NOTE_G5 = 784
                                            NOTE_GS5 = 831
                                            NOTE_A5 = 880
                                            NOTE_AS5 = 932
                                            NOTE_B5 = 988
                                            NOTE_C6 = 1047
                                            NOTE_CS6 = 1109
                                            NOTE_D6 = 1175
                                            NOTE_DS6 = 1245
                                            NOTE_E6 = 1319
                                            NOTE_F6 = 1397
                                            NOTE_FS6 = 1480
                                            NOTE_G6 = 1568
                                            NOTE_GS6 = 1661
                                            NOTE_A6 = 1760
                                            NOTE_AS6 = 1865
                                            NOTE_B6 = 1976
                                            NOTE_C7 = 2093
                                            NOTE_CS7 = 2217
                                            NOTE_D7 = 2349
                                            NOTE_DS7 = 2489
                                            NOTE_E7 = 2637
                                            NOTE_F7 = 2794
                                            NOTE_FS7 = 2960
                                            NOTE_G7 = 3136
                                            NOTE_GS7 = 3322
                                            NOTE_A7 = 3520
                                            NOTE_AS7 = 3729
                                            NOTE_B7 = 3951
                                            NOTE_C8 = 4186
                                            NOTE_CS8 = 4435
                                            NOTE_D8 = 4699
                                            NOTE_DS8 = 4978
                                            REST = 0
                                            
                                            # Buzzer pin (change this depending on your setup)
                                            buzzer_pin = machine.Pin(27, machine.Pin.OUT)  # Pin 15 on the Xiao RP2040
                                            
                                            # Create a PWM object to control the buzzer
                                            buzzer = machine.PWM(buzzer_pin)
                                            
                                            # Melody with notes and durations
                                            melody = [
                                                (REST, 2), (NOTE_D4, 4),
                                                (NOTE_G4, -4), (NOTE_AS4, 8), (NOTE_A4, 4),
                                                (NOTE_G4, 2), (NOTE_D5, 4),
                                                (NOTE_C5, -2), 
                                                (NOTE_A4, -2),
                                                (NOTE_G4, -4), (NOTE_AS4, 8), (NOTE_A4, 4),
                                                (NOTE_F4, 2), (NOTE_GS4, 4),
                                                (NOTE_D4, -1), 
                                                (NOTE_D4, 4),
                                                (NOTE_G4, -4), (NOTE_AS4, 8), (NOTE_A4, 4),
                                                (NOTE_G4, 2), (NOTE_D5, 4),
                                                (NOTE_F5, 2), (NOTE_E5, 4),
                                                (NOTE_DS5, 2), (NOTE_B4, 4),
                                                (NOTE_DS5, -4), (NOTE_D5, 8), (NOTE_CS5, 4),
                                                (NOTE_CS4, 2), (NOTE_B4, 4),
                                                (NOTE_G4, -1),
                                                (NOTE_AS4, 4),
                                                (NOTE_D5, 2), (NOTE_AS4, 4),
                                                (NOTE_D5, 2), (NOTE_AS4, 4),
                                                (NOTE_DS5, 2), (NOTE_D5, 4),
                                                (NOTE_CS5, 2), (NOTE_A4, 4),
                                                (NOTE_AS4, -4), (NOTE_D5, 8), (NOTE_CS5, 4),
                                                (NOTE_CS4, 2), (NOTE_D4, 4),
                                                (NOTE_D5, -1), 
                                                (REST, 4), (NOTE_AS4, 4),
                                                (NOTE_D5, 2), (NOTE_AS4, 4),
                                                (NOTE_D5, 2), (NOTE_AS4, 4),
                                                (NOTE_F5, 2), (NOTE_E5, 4),
                                                (NOTE_DS5, 2), (NOTE_B4, 4),
                                                (NOTE_DS5, -4), (NOTE_D5, 8), (NOTE_CS5, 4),
                                                (NOTE_CS4, 2), (NOTE_AS4, 4),
                                                (NOTE_G4, -1),
                                            ]
                                            
                                            # Song speed (adjust if necessary)
                                            tempo = 144
                                            
                                            # Duration of a whole note (in milliseconds)
                                            wholenote = (60000 * 4) / tempo
                                            
                                            def play_tone(frequency, duration):
                                                if frequency > 0:
                                                    buzzer.freq(frequency)  # Set the frequency for the buzzer
                                                    buzzer.duty_u16(32768)  # Control the intensity (50% intensity with duty_u16)
                                                    time.sleep(duration / 1000)  # Play the note for the appropriate time
                                                    buzzer.duty_u16(0)  # Turn off the sound after the duration
                                            
                                            def play_melody():
                                                for note, duration in melody:
                                                    if note == REST:
                                                        time.sleep(wholenote / duration / 1000)  # Pause based on the note duration
                                                    else:
                                                        # Calculate the note duration
                                                        note_duration = wholenote / duration
                                                        play_tone(note, note_duration)
                                            
                                            # Play the melody in the main loop
                                            while True:
                                                play_melody()
                                                time.sleep(1)  # A break before repeating the song (if needed)

For this project, while researching, I came across my instructor Cristian's work and I really liked the code he used for the Imperial March from Star Wars, written by Robson Couto (2019). I decided to take on the challenge, as he used Arduino IDE, while I am working with MicroPython in the Thonny program.

I visited the following link: Git Hub - Robson Couto because I wanted to make Hedwig's Theme from Harry Potter. I copied the code and used the ChatGPT tool for adjustments.

Did I face any difficulties?

Yes, I encountered some difficulties. The original code was written for Arduino IDE, and I needed to adapt it for MicroPython in the Thonny environment. When making the adaptation, I forgot to include the technical specifications of the microcontroller I was using. Once identified, I used the prompt: "convert Arduino code to MicroPython for a Xiao RP2040 with pin 27."

However, the code still didn’t work properly. I received the following error:

>>> %Run -c $EDITOR_CONTENT

MPY: soft reboot
Traceback (most recent call last):
    File "", line 162, in 
    File "", line 158, in play_melody
    File "", line 147, in play_tone

It appeared that the issue was because the PWM class in MicroPython for the Xiao RP2040 doesn't have a method called duty. Instead, you should use duty_u16() to set the PWM intensity value, which accepts a range from 0 to 65535, unlike the duty() method commonly used in other microcontrollers like the ESP32.

After making this adjustment, the code started working correctly.

Finally, Hedwig's Theme from Harry Potter plays correctly on the buzzer I connected. After making the necessary adjustments to the code and properly connecting the components, I managed to get the buzzer to play the melody. Now the system works as expected, and the sound is just right for the song.

2. SG90 servo motor

For the second exercise, I will be using an SG90 servomotor, a precision electric motor specifically designed to control angular movement in applications that require exact position control. Unlike conventional motors, the SG90 servomotor is characterized by its ability to move an axis within a limited rotation range, typically from 0 to 180 degrees, which makes it an ideal choice for tasks that demand controlled and repetitive movements.

Now, I will proceed to connect the SG90 servomotor to my PCB, for which it is important to recognize the correct connections. The GND (ground) should be connected to the GND of the board, ensuring a common voltage reference between the servomotor and the board. The VCC is the voltage input to power the servomotor, and in this case, it should be connected to 5V to provide the appropriate power. Finally, the PWM pin is responsible for receiving the control signal to set the servomotor's position. In this case, I will connect the PWM to pin 29 of the board, which will send the pulse-width modulation (PWM) signals necessary to control the servomotor's rotation angle.

Now, I will connect the components I have. I will make sure all connections are correct for everything to work properly.

                                            from machine import Pin, PWM
from time import sleep

servo = PWM(machine.Pin(29)) # Set up PWM Pin for servo control
max_duty = 7864  # Set Duty Cycle for Different Angles
min_duty = 1802
half_duty = int(max_duty/2)
servo.freq (50)  #Set PWM frequency

try:
    while True:
        servo.duty_u16(min_duty)  #Servo at 0 degrees
        sleep(2)
        servo.duty_u16(half_duty) #Servo at 90 degrees
        sleep(2)
        servo.duty_u16(max_duty)  #Servo at 180 degrees
        sleep(2)    
      
except KeyboardInterrupt:
    print("Keyboard interrupt")
    servo.deinit() # Turn off PWM

The code I will use is the one taught by instructor Ulises during a masterclass he led.

This is the result of the SG90 servo motor connected to the XIAO RP2040 microcontroller.

Reflections

Working with the buzzer, I learned several key lessons about how these components function and how to measure them to understand their behavior. A buzzer is a device that emits sound when an electrical signal is applied.

One of the first observations I made was that the buzzer has a very low power consumption, making it difficult to measure accurately with a standard multimeter, especially when measuring in amperes of direct current (DCA). This led me to reflect on the difference between a multimeter and a specialized power meter. A power meter could provide more accurate readings of energy consumption in low-power devices like the buzzer.

Additionally, I learned that a buzzer can be powered by either direct or alternating current, and that its operating frequency, which determines the pitch of the sound emitted, is influenced by the electrical signal it receives. Measuring the buzzer allowed me to see how small changes in current or voltage directly affect its operation, and how the multimeter, although useful, has certain limitations when measuring components with low current demand.

Access to files

HarryPotter

Servomotor