RAVI'S PAINTBRUSH CLEANER

Key Concepts

• Mechanical Advantage: Designing mounting systems that increase efficiency and decrease strain on the servo
• Motion Patterns: Different agitation patterns' effectiveness for various brush types and paint consistencies
• Input Systems: Designing accessible buttons and controls for users with muscular weakness
• Program Structure: Using functions, variables, and loops to create adaptable code

Activity: "Design Decision Matrix"

1. Compile Findings:
   • Teams present their motion experiments and observations
   • Create a class list of effective motion patterns for different brush types
2. Create Design Criteria:
   • Guide students to develop specific criteria for their solutions:
     • Must clean standard paintbrushes in under 30 seconds
     • Must be easily activated by someone with limited hand strength
     • Must operate without supervision once activated
     • Must be stable and not tip during operation
     • Must be adjustable for different water containers and brush sizes
3. Introduce Advanced Servo Control:
   • Demonstrate button control for servo activation
   • Show how to add timing components to automatically stop after cleaning
   • Explain LED feedback for operational states

import time
import board
import pwmio
import servo
from digitalio import DigitalInOut, Direction, Pull
import neopixel

# Set up servo
pwm = pwmio.PWMOut(board.A2, duty_cycle=2 ** 15, frequency=50)
my_servo = servo.Servo(pwm)

# Set up button
button = DigitalInOut(board.D2)
button.direction = Direction.INPUT
button.pull = Pull.UP

# Set up Neopixel LED
pixel = neopixel.NeoPixel(board.NEOPIXEL, 1)
pixel.brightness = 0.3

# Function for brush cleaning cycle with LED feedback
def clean_brush_cycle():
    # Blue means running
    pixel[0] = (0, 0, 255)
    
    # Do 10 cycles of cleaning motion
    for c in range(10):
        # Forward motion
        for angle in range(45, 135, 5):
            my_servo.angle = angle
            time.sleep(0.05)
        # Backward motion
        for angle in range(135, 45, -5):
            my_servo.angle = angle
            time.sleep(0.05)
    
    # Green means complete
    pixel[0] = (0, 255, 0)
    # Return to neutral position
    my_servo.angle = 90
    # Wait a bit with green light on
    time.sleep(3)
    # Turn off LED
    pixel[0] = (0, 0, 0)

# Main loop
while True:
    # Yellow means ready
    pixel[0] = (255, 255, 0)
    
    # Check if button is pressed
    if not button.value:  # Button pressed (reads False when pressed)
        time.sleep(0.1)  # Debounce
        if not button.value:  # Still pressed after debounce
            clean_brush_cycle()
    
    time.sleep(0.1)  # Small delay in main loop

Activity: "Prototype Refinement and Testing"

1. CAD Design Work:
   • Guide students to design mounting components in OnShape
   • Create brackets, brush holders, and button mounts
   • Prepare files for 3D printing
2. Physical Construction:
   • Assemble servo mounting systems using LocLine and framing pieces
   • Incorporate 3D printed components
   • Set up button placement for easy access
3. Code Refinement:
   • Add customization options to the code
   • Implement multiple cleaning modes for different brush types
   • Create error handling for when buttons are held too long

import time
import board
import pwmio
import servo
from digitalio import DigitalInOut, Direction, Pull
import neopixel

# Setup hardware
pwm = pwmio.PWMOut(board.A2, duty_cycle=2 ** 15, frequency=50)
my_servo = servo.Servo(pwm)
button = DigitalInOut(board.D2)
button.direction = Direction.INPUT
button.pull = Pull.UP
mode_button = DigitalInOut(board.D3)
mode_button.direction = Direction.INPUT
mode_button.pull = Pull.UP
pixel = neopixel.NeoPixel(board.NEOPIXEL, 1)
pixel.brightness = 0.3

# Variables
current_mode = 0  # 0=gentle, 1=medium, 2=thorough
mode_colors = [(0, 100, 255), (100, 100, 255), (150, 0, 255)]  # Colors for each mode
cleaning = False

# Cleaning mode parameters
modes = [
    {"cycles": 5, "speed": 0.08, "angle_min": 60, "angle_max": 120},    # Gentle
    {"cycles": 10, "speed": 0.05, "angle_min": 45, "angle_max": 135},   # Medium
    {"cycles": 15, "speed": 0.03, "angle_min": 30, "angle_max": 150}    # Thorough
]

# Function to run a cleaning cycle
def clean_brush_cycle(mode_settings):
    global cleaning
    cleaning = True
    
    # Blue means running
    pixel[0] = (0, 0, 255)
    
    # Run the specified number of cycles
    for c in range(mode_settings["cycles"]):
        # Forward motion
        for angle in range(mode_settings["angle_min"], mode_settings["angle_max"], 5):
            my_servo.angle = angle
            time.sleep(mode_settings["speed"])
        # Backward motion
        for angle in range(mode_settings["angle_max"], mode_settings["angle_min"], -5):
            my_servo.angle = angle
            time.sleep(mode_settings["speed"])
    
    # Green means complete
    pixel[0] = (0, 255, 0)
    # Return to neutral position
    my_servo.angle = 90
    # Wait a bit with green light on
    time.sleep(3)
    # Turn off LED
    pixel[0] = (0, 0, 0)
    cleaning = False

# Main loop
while True:
    if not cleaning:
        # Show current mode color
        pixel[0] = mode_colors[current_mode]
    
    # Check if mode button is pressed
    if not mode_button.value and not cleaning:
        time.sleep(0.1)  # Debounce
        if not mode_button.value:  # Still pressed after debounce
            # Change to next mode
            current_mode = (current_mode + 1) % len(modes)
            # Flash the new mode color
            pixel[0] = (0, 0, 0)
            time.sleep(0.2)
            pixel[0] = mode_colors[current_mode]
            time.sleep(0.5)
    
    # Check if start button is pressed
    if not button.value and not cleaning:  # Button pressed and not already cleaning
        time.sleep(0.1)  # Debounce
        if not button.value:  # Still pressed after debounce
            clean_brush_cycle(modes[current_mode])
    
    time.sleep(0.1)  # Small delay in main loop

Assessment Activities

1. User Testing Simulation:
   • Teams test their devices with various paintbrushes and water containers
   • One student role-plays as Ravi, providing feedback
   • Document performance against design criteria
2. Technical Performance Assessment:
   • Measure cleaning effectiveness with different brush types
   • Test button activation force requirements
   • Evaluate stability and reliability during operation
3. Design Documentation and Presentation:
   • Teams create documentation of their final designs
   • Prepare short presentations explaining their design decisions
   • Include suggestions for future improvements

Assessment Rubric