Touch Piano¶

Interactive musical experience using conductive materials connected to GPIO pins. Learn about circuits while making music!

Overview¶

The Touch Piano transforms everyday conductive materials into musical keys. Students learn about circuits, conductivity, and music while having fun.

URL: /plugins/edupi/touch_piano/

Hardware Requirements¶

6 touch sensors or capacitive touch inputs
Conductive materials (bananas, foil, copper tape, etc.)
Speaker or headphones (3.5mm jack)
6x 10kΩ pull-up resistors (if using bare wire)
Breadboard and jumper wires

GPIO Pin Connections¶

6 Piano Keys:

Key	Note	GPIO Pin	Physical Pin	Wire Color
Key 1	C (Do)	23	16	Red
Key 2	D (Re)	24	18	Orange
Key 3	E (Mi)	10	19	Yellow
Key 4	F (Fa)	9	21	Green
Key 5	G (Sol)	25	22	Blue
Key 6	A (La)	11	23	Purple

How It Works¶

Capacitive Touch Sensing¶

The Touch Piano uses capacitive touch sensing to detect when conductive materials are touched:

Circuit Setup: Conductive material connected to GPIO pin
Pull-up Resistor: Maintains HIGH state when not touched
Touch Detection: When touched, capacitance changes
Signal Processing: GPIO detects the change and triggers note
Audio Output: pygame synthesizes and plays the note

Conductive Materials¶

Many everyday items work as piano keys:

Material	Conductivity	Best For
Bananas	Excellent	Fun demonstrations
Aluminum Foil	Excellent	Custom shapes
Copper Tape	Excellent	Permanent installations
Play-Doh	Good	Child-safe
Water	Moderate	Science experiments
Plants	Moderate	Living piano

Best Results

Moist materials (like fresh fruit) work better than dry materials.

Interface¶

Piano Display¶

The web interface shows a 6-key piano:

Visual Keys: Click to play
Key Labels: Shows note names (C, D, E, F, G, A)
Status: Shows which key is currently pressed
Volume Control: Adjust output level

Keyboard Shortcuts¶

Play using your computer keyboard:

Computer Key	Piano Key	Note
A	Key 1	C
S	Key 2	D
D	Key 3	E
F	Key 4	F
G	Key 5	G
H	Key 6	A

Building the Circuit¶

Option 1: Simple Wire Connection¶

Connect GPIO pins to conductive materials with wire
Add 10kΩ pull-up resistors between each pin and 3.3V
Connect common ground
Touch material to play

Option 2: Using Capacitive Touch Sensors (TTP223)¶

Connect TTP223 modules to GPIO pins
Connect sensor outputs to materials
No pull-up resistors needed
More reliable touch detection

Wiring Diagram¶

GPIO 23 (Pin 16) ----[10kΩ]---- 3.3V (Pin 1)
     |
     +---- Wire to banana/foil

Repeat for all 6 keys

Safety

Always use 3.3V power, not 5V. High voltage can damage GPIO pins.

Learning Objectives¶

Science Concepts¶

Conductivity: What materials conduct electricity?
Circuits: How do circuits work?
Resistance: Why do some materials work better?
Capacitance: How does touch sensing work?

Music Concepts¶

Pitch: Higher/lower notes
Octaves: Scale relationships
Melody: Creating simple tunes
Rhythm: Timing and beats

Technology Concepts¶

GPIO: General Purpose Input/Output
Digital Input: Reading on/off states
Audio Synthesis: Creating sounds programmatically
Human-Computer Interaction: Physical computing

Configuration Options¶

Access settings via Settings > Touch Piano:

Volume¶

Range: 0-100%
Default: 80%
Adjust based on classroom noise level

Audio Device¶

default: System default audio
hw:0,0: Hardware device 0
plughw:1,0: USB audio device

To list available devices:

aplay -l

Sensitivity¶

Range: 1-10
Default: 5
Higher = more sensitive touch detection
Increase if touches aren't registering
Decrease if getting false triggers

Visual Feedback¶

Enable/disable web interface highlighting
Shows which key is pressed
Helpful for debugging

Session Tracking¶

The Touch Piano tracks playing sessions:

Session start/end times
Key press counts per key
Total play duration
Most frequently used keys

View statistics in the plugin interface.

Classroom Activities¶

Activity 1: Circuit Discovery¶

Objective: Identify conductive materials

Gather various objects (pencil, eraser, coin, foil, etc.)
Test each with the piano
Sort into "conductive" and "non-conductive" piles
Discuss why some work and others don't

Activity 2: Build a Banana Piano¶

Objective: Create a working musical instrument

Connect 6 bananas to GPIO pins
Test each banana-key
Play simple songs (Twinkle Twinkle, etc.)
Experiment with different fruits

Activity 3: Copper Tape Art¶

Objective: Create permanent touch pads

Design piano key shapes on cardboard
Apply copper tape to create touch areas
Connect to GPIO pins
Play and decorate your custom piano

Activity 4: Science of Sound¶

Objective: Understand pitch and frequency

Play each key, note the pitch
Compare high vs low notes
Discuss why C is lower than A
Create simple melodies

Troubleshooting¶

No Sound¶

Check speaker connection
Verify volume > 0%
Test audio device: speaker-test
Check pygame audio initialization

Keys Not Responding¶

Check wire connections
Verify GPIO pin numbers
Test with multimeter
Increase sensitivity in settings

Intermittent Touch Detection¶

Check for loose connections
Ensure good contact with material
Increase sensitivity
Use more conductive materials (fruit vs foil)

False Triggers¶

Decrease sensitivity
Check for electrical interference
Ensure proper grounding
Add capacitors for filtering (advanced)

One Key Not Working¶

Test that specific GPIO pin
Check wire continuity
Verify resistor connection
Swap with working key to isolate issue

Best Practices¶

Material Selection¶

Fresh fruit works best (higher moisture content)
Avoid very dry materials
Test materials before class
Have backups ready

Setup Tips¶

Label connections: Mark which wire goes to which key
Secure wires: Prevent accidental disconnections
Stable surface: Place materials on flat surface
Common ground: Ensure all users touch ground reference

Safety¶

Use only 3.3V GPIO pins
Keep water away from electronics
Supervise younger students
Don't touch bare wires with wet hands

Maintenance¶

Check connections before each use
Replace worn wires
Clean contacts if using metal materials
Update materials (fruit gets old!)

Advanced Topics¶

Custom Key Mappings¶

Edit plugin.py to change notes:

notes = {
    'key_1': 'C4',
    'key_2': 'D4',
    'key_3': 'E4',
    'key_4': 'F4',
    'key_5': 'G4',
    'key_6': 'A4',
}

Adding More Keys¶

Requires hardware modification and code changes. See plugin development guide.

MIDI Output¶

Can be configured to output MIDI signals for external synthesizers.

Technical Details¶

Audio: pygame.midi for synthesis
GPIO: gpiozero for input detection
Sampling: 60Hz touch detection
Debounce: 50ms to prevent multiple triggers
Auto-cleanup: Stuck notes timeout after 5 seconds

GPIO Wiring - Detailed hardware setup
Dashboard - Access the piano
Settings - Configure piano options
Plugin Development - Customize the piano