actuators - Working with Actuators

The actuators module provides a collection of classes to interact with actuators, such as servos, relays, and buttons.

Servo

class actuators.Servo(port[=2], position[=0])

Allows control of a Grove Servo. Default port for the servo is 2. The position parameter sets the initial position of the servo.

Servo.set_position(degree)

Sets the degree position of the servo (between 0 and 180, which is half a circle). If degree is greater than 180, the servo will be set at the 180 degree position. Likewise, if degree is less than 0, the servo will rotate to the 0 degree position.

Servo.get_position()

Returns the current position of the servo in degrees.

Example:

from actuators import Servo

s = Servo(1, init_degree = 180) # defines a servo connected to port 1 with initial position at 180 degrees.
s.set_position(90) # rotate the servo by 90 degrees.

Relay

class actuators.Relay(port[=1])

Allows control of a Grove Relay. The relay by default is normally open (NO) triggered by a high signal.

Relay.on()

Activate the relay, close the circuit, and turn on whatever appliance that’s connected to the relay.

Relay.off()

Deactivate the relay, open the circuit, and turn off whatever appliance that’s connected to the relay.

Relay.is_on()

Returns True if the relay is on, or False if the relay is off.

Button

class actuators.Button(port[=2], pullup[=True])

Allows control of a Grove Button. There are two ways to use a button. First, you can access Button.is_pressed property or Button.is_pressed() method to determine if the button is pressed. Alternatively, you can also set a callback function with Button.on_release() method use the interrupt mechanism. Please see example of how to use the callback.

Button.is_pressed()

Returns True if the button is pressed, or False if it is not.

Button.on_press(callback)

Executes the callback function provided to the method when the button is pressed.

Button.on_release(callback)

Executes the callback function provided to the method when the button is released.

Example

Controlling the LED with the Button

from actuators import Led, Button
led = Led(1) # Specifies an LED at Port 1
button = Button(2) # Specifies a button at Port 2

## Turns on the LED when the button is pressed

while True:

    if button.is_pressed():
        led.on()
    else:
        led.off()

Turns the LED on/off with a callback function

from actuators import Button
from displays import Led
led = Led(1, on=False) # Specifies an LED at Port 1
button = Button(2) # Specifies a button at Port 2

## Define a callback function

def turn_on_led(pin):
    global led # Need this line to refer to the led object outside the function.

    if led.is_on():
        led.off()
    else:
        led.on()

## Set the callback function to Button.on_release method.

button.on_release(callback=turn_on_led) # Note that no () are needed.

Buzzer

class actuators.Buzzer(port[=2])

Allows control of a Grove Buzzer. You can control the buzzer to play a note or a piece of music. The notes are written in strings. Available notes are ["c", "d", "e", "f", "g", "a", "b", "C", " "]. White space means skip.

Buzzer.play_note(note, duration[=0.5])

Plays a note. duration controls how long the note gets played.

Buzzer.play_music(notes, rhythms[=None], tempo[=1])

Plays a string of notes. You may supply a list of numbers the same length as notes as rhythms, how long each note gets played. You may also specify an overall tempo. The larger tempo is, the slower the music.

Example

Using the buzzer

from actuators import Buzzer
buzzer = Buzzer(port=2)

# Plays one note

buzzer.play_note("c", duration=1)

# Plays a piece of music

buzzer.play_music("cdefgabC", rhythms=[32, 16, 8, 4, 2, 1, 0.5, 1], tempo = 0.8)