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9. Output devices

Group assignment:

  • Measure the power consumption of an output device.

  • Document your work to the group work page and reflect on your individual page what you learned

To see our group assignment click here

Individual assignment:

  • Add an output device to a microcontroller board you’ve designed and program it to do something.

Hi! For this week, we’ve chosen a servomotor and DC motor with the board we designed for the mission.

Servomoteur

A servomotor is a device used in many systems to precisely control the position, speed or acceleration of a mechanism. It usually consists of an electric motor, a control circuit and a feedback mechanism.

Circuit diagram

Using the board we’ve designed, we’ve wired up our servomotor, and used a buzzer to produce a sound when the servomotor rotates.

TEST 1

We’ve written code in micropython using the Thonny editor introduced in Week 6.

Code

Library

from machine import Pin, PWM
import time

Definition of the GPIO pin to which the servomotor is connected

servo_pin = Pin(3)
buzzer_pin = Pin(4, Pin.OUT)  # Définition de la broche GPIO pour le buzzer

PWM initialization for servomotor control

servo_pwm = PWM(servo_pin, freq=50)

def set_angle(angle):

Conversion of angle to PWM pulse width (500 to 2500 µs for a range of 0 to 180 degrees)

    pulse_width = int((angle / 180.0) * (2500 - 500) + 500)
    servo_pwm.duty_u16(pulse_width * 65536 // 20000)  # Conversion de la largeur d'impulsion en degrés

def play_train_sound():
    # Jouer un son de train
    buzzer_pin.on()
    time.sleep_ms(100)
    buzzer_pin.off()
    time.sleep_ms(50)

while True:
    # Faire tourner le servomoteur de 0 à 180 degrés
    for angle in range(0, 181, 10):
        set_angle(angle)
        play_train_sound()  # Jouer le son de train
        time.sleep_ms(10)  # Attendre 30 ms pour que le servomoteur atteigne la position

    # Faire tourner le servomoteur de 180 à 0 degrés
    for angle in range(180, -1, -10):
        set_angle(angle)
        play_train_sound()  # Jouer le son de train
        time.sleep_ms(10)  # Attendre 30 ms pour que le servomoteur atteigne la position

TEST 1 Result

TEST 2

We’re going to program a DC motor using the board we’ve designed and a driver.

DC motor

Module L298N

The L298N module is a popular double H-bridge motor controller used to control the speed and direction of DC motors and bipolar stepper motors.

Circuit diagram

Code

Library

//*******************************************************************************//
// Association of the L298N inputs with the outputs used on our Arduino Uno //
//*******************************************************************************//
import machine
import utime

Pin definition

borneENA = machine.PWM(machine.Pin(26))
borneIN1 = machine.Pin(27, machine.Pin.OUT)
borneIN2 = machine.Pin(28, machine.Pin.OUT)
borneIN3 = machine.Pin(29, machine.Pin.OUT)
borneIN4 = machine.Pin(6, machine.Pin.OUT)
borneENB = machine.PWM(machine.Pin(5))
Program constants

delaiChangementVitesse = 20
vitesseMinimale = 60
vitesseMaximale = 200

Direction of rotation

MARCHE_AVANT = 'V'
MARCHE_ARRIERE = 'R'

Direction of rotation setting function

def configurerSensDeRotationPontA(sensDeRotation):
    if sensDeRotation == MARCHE_AVANT:
        borneIN1.value(1)
        borneIN2.value(0)
    elif sensDeRotation == MARCHE_ARRIERE:
        borneIN1.value(0)
        borneIN2.value(1)

Motor speed change function

def changeVitesseMoteurPontA(nouvelleVitesse):
    borneENA.duty_u16(nouvelleVitesse * 256)  # Le RP2040 utilise une résolution de 16 bits pour le PWM

Output pin configuration

borneENA.freq(1000)  # PWM signal frequency
borneENB.freq(1000)
borneIN1.value(0)
borneIN2.value(0)
borneIN3.value(0)
borneIN4.value(0)

Main loop

while True:
    # MARCHE AVANT
    configurerSensDeRotationPontA(MARCHE_AVANT)
    for vitesse in range(vitesseMinimale, vitesseMaximale):
        changeVitesseMoteurPontA(vitesse)
        utime.sleep_ms(delaiChangementVitesse)

    for vitesse in range(vitesseMaximale, vitesseMinimale, -1):
        changeVitesseMoteurPontA(vitesse)
        utime.sleep_ms(delaiChangementVitesse)

    # Pause
    changeVitesseMoteurPontA(0)
    utime.sleep(1)

    # MARCHE ARRIERE
    configurerSensDeRotationPontA(MARCHE_ARRIERE)
    for vitesse in range(vitesseMinimale, vitesseMaximale):
        changeVitesseMoteurPontA(vitesse)
        utime.sleep_ms(delaiChangementVitesse)

    for vitesse in range(vitesseMaximale, vitesseMinimale, -1):
        changeVitesseMoteurPontA(vitesse)
        utime.sleep_ms(delaiChangementVitesse)

    # Pause
    changeVitesseMoteurPontA(0)
    utime.sleep(1)
TEST 2 Result

in reality, this is the type of motor we’re going to use for our robot’s navigation, so we’ve decided to write a program to see how it works.

this link will take you to a video of the robot being navigated by the motor

File source

End

Last update: July 17, 2024