Day 23: (Wed Nov 20, Week 13) Revision Testing

Assignments

Please remember to collect ongoing documentation. Please use Project Phase 2 Folder.

Administrative

If your prototype will require 3D-printed parts, I can individually show you how to export an STL and submit to the Mosaic printer system using CKS-F24 3D Printer Submissions.

Short term schedule:

Date	Due
Mon Nov 18	new proof of concept or design revision
Mon Nov 25	dress rehearsal (before Thanksgiving)
Mon Dec 4	revised prototype to test at School

Agenda

1. General project status check

2. Revision demo and testing

3. Individual consultations

References

1. For the motor drive, we can use the MOSFET circuit and sample code from DC Motor Examples - Raspberry Pi Pico.

2. For the button circuit, we can use the example from Exercise: Digital I/O with the Pico.

3. For the button inputs, we can use the sample code from Digital Input/Output Examples - Raspberry Pi Pico.

Sample Code

The combined sample code for the puppet machine can be found at puppet-show.py. It should be renamed code.py when copied to the Pico.

# puppet-show.py

# Sample code for operating a mechanical puppet show.  Two pushbutton switches
# and two indicator LEDS are attached as the user interface.  A single MOSFET
# transistor drive circuit switches on all the DC motor.

# Related documentation:
# https://circuitpython.readthedocs.io/en/latest/shared-bindings/pwmio/index.html#module-pwmio

# Wiring notes:

# GPIO22 - pin 29 - PWM output to MOSFET
#
# GPIO12 - pin 16 - input from start switch
# GPIO13 - pin 17 - input from stop switch
# GND    - pin 18
# GPIO14 - pin 19 - output to start LED
# GPIO15 - pin 20 - output to stop LED

# ----------------------------------------------------------------
# Import standard Python modules.
import time, math

# Load the CircuitPython hardware definition module for pin definitions.
import board

# Load the CircuitPython pulse-width-modulation module for driving hardware.
import pwmio

# Load the CircuitPython digital input/output module for reading and writing pin voltages.
import digitalio

# ----------------------------------------------------------------
# Initialize hardware.

# Create a PWMOut object on GP22.  This will create a pulsing signal with
# variable duty cycle.  The switching rate of 20kHz is chosen to be
# supra-audible.
pwm = pwmio.PWMOut(board.GP22, duty_cycle=0, frequency=20000)

# Utility function to calculate and apply a new duty cycle setting.  Converts a
# unit-range (0.0 to 1.0) pwm_level to a 16-bit integer representing a fraction
# needed by the PWM driver.
def set_motor_speed(pwm_device, pwm_level):
    pwm_device.duty_cycle = min(max(int(pwm_level * 2**16), 0), 2**16-1)
    print("Applied duty cycle of %d for pwm_level %f" % (pwm_device.duty_cycle, pwm_level))

# ----------------------------------------------------------------
# Set up digital inputs.

start_switch = digitalio.DigitalInOut(board.GP12)
start_switch.direction = digitalio.Direction.INPUT

stop_switch = digitalio.DigitalInOut(board.GP13)
stop_switch.direction = digitalio.Direction.INPUT

# Set up digital inputs.

start_LED = digitalio.DigitalInOut(board.GP14)
start_LED.direction = digitalio.Direction.OUTPUT

stop_LED = digitalio.DigitalInOut(board.GP15)
stop_LED.direction = digitalio.Direction.OUTPUT

# ----------------------------------------------------------------
# Enter the main event loop.
while True:

    # turn on stop LED
    stop_LED.value = True

    # wait for start switch; it is wired active-low, so it will become False when pressed
    while start_switch.value is True:
        pass

    # turn off stop LED, turn on start LED
    stop_LED.value = False
    start_LED.value = True

    # turn the motor on
    set_motor_speed(pwm, 1.0)

    # wait for stop switch; it is wired active-low, so it will become False when pressed
    while stop_switch.value is True:
        pass

    # turn the motor off again
    set_motor_speed(pwm, 0.0)

    # turn off start LED
    start_LED.value = False