Manuel Ignacio Ayala Chauvin

1. Introduction

This project proposes a smart, customizable puppet that combines creativity, education, technology, and emotional interaction into a single innovative platform. The conceptual structure demonstrates how the puppet becomes an advanced educational tool that drives children's narrative development, artistic expression, and autonomous learning.

The system not only allows for physical customization of the character (by changing eyes, mouths, hair, and noses), but also synchronizes the user’s voice with expressive movements, creating an immersive storytelling experience.

Final Project Dissemination Plan

Technical Infographic: This diagram illustrates the development workflow of the puppet system. From CNC-cut wooden base and circuit design in KiCad, to signal amplification with an LM358 and testing with an oscilloscope. The signal amplitude controls mouth motion, and the final prototype is tested with voice signals to validate mechanical response.

Illustrated Infographic: This playful diagram shows how the puppet moves its mouth in sync with speech. A hidden narrator speaks into a microphone while the puppet tells the story to children. The modular design allows for quick character changes using swappable masks, such as an elephant, lion, or pig.

1.1. Key Elements of the Concept

1.1.1. Audio Synchronization with Motion Control

The puppet integrates an audio synchronization system that analyzes voice signals and controls mouth movement through signal processing algorithms. This technical capability ensures audio-visual coherence between speech and puppet movement, enhancing realism and immersion.

Impact: Improves puppet expressiveness, fostering emotional connection with the audience.

1.1.2. Motion Control Mechanism

Mouth opening and closing are achieved through a four-bar linkage mechanism, powered by a precision motor. This mechanical solution guarantees smooth, efficient, and repeatable movements, with low energy consumption and high reliability.

Impact: Allows for a compact, lightweight, and easily maintainable design, ideal for educational and recreational use.

1.1.3. Character Changes

The puppet is designed as a customizable platform. Children can modify its appearance by swapping parts (eyes, mouths, noses, hair) to create:

• Real animals
• Fantasy creatures
• Unique characters from their imagination

Impact: Stimulates creativity, encourages divergent thinking, and provides unique experiences for each user.

1.1.4. Mobile App for Control and Story Adaptation

An intuitive mobile app allows users to:

• Upload voice recordings or stories
• Activate the puppet’s synchronized movement
• Adapt storytelling in real time

Impact: Promotes early digital literacy and the use of emerging technologies in educational contexts.

1.1.5. Educational Impact

The project strongly focuses on educational skills development:

• Narrative and oral expression: Children learn to tell structured stories.
• Literacy: Stories can be transcribed into small books or digital stories.
• Creative and emotional thinking: Creating characters and stories stimulates empathy, self-awareness, and imagination.

Impact: Integrates as a pedagogical tool in basic and special education programs.

1.1.6. Story Documentation and Book Production

The system promotes the documentation of created stories in written form (books, illustrated stories), reinforcing reading and writing skills.

Impact: Completes the creative cycle from oral storytelling to literary production.

Character examples

The following illustrations, created by my son Emanuel, represent a key part of the creative development process proposed in the system: moving from oral storytelling and imagination to tangible literary production.

Character 1: The Wise Tiger

This character portrays a wise, serene tiger. The slightly closed eyes and the serious, yet calm, expression suggest intelligence and a deep understanding of his surroundings. His vivid orange and dark stripes evoke strength, while the tufts of white hair represent age and wisdom. This character could symbolize the guide or mentor figure within Emanuel's story narrative.

Character 2: The Wild Beast

With a wild mane and hypnotic spiral eyes, this character radiates chaotic energy. The jagged teeth and mischievous smile hint at a mischievous, perhaps unpredictable creature. Emanuel's use of rough strokes and intense contrast between orange and black emphasize the beast's untamed nature. This figure could serve as the story's antagonist or an uncontrollable force that the protagonists must face.

Character 3: The Happy Elephant

Bright and cheerful, the blue elephant stands out with its exaggerated features: large, floppy ears and a long trunk. The wide, smiling mouth conveys joy and innocence. Through this character, Emanuel captures the essence of kindness and loyalty, often associated with elephants. In the story, this character could represent a faithful companion who brings support and comic relief to the adventure.

Character 4: The Playful Pig

Finally, the playful pig exhibits a lively and carefree personality. With one eye larger than the other and a tilted head, the character projects curiosity and a bit of mischief. The vibrant pink coloring makes it instantly endearing. This figure could symbolize a mischievous friend or the adventurous spirit that propels the story forward.

1.1.7. Strategic Conclusion

The customizable interactive puppet is far more than a toy: It is a platform for creative and educational development, designed to build essential 21st-century skills in children. It integrates precision mechanics, audio processing, mobile technology, and pedagogical dynamics into a powerful and scalable system.

Unique Value Proposition:

• Experiential learning through creativity
• Full customization of characters and narratives
• Genuine integration of educational and emotional technology
• Future expansion with new movement modules (eyes, hands)

2. General Objective

To develop a customizable interactive puppet that integrates audio synchronization technologies, motion control mechanisms, and a mobile application, with the purpose of enhancing creativity, oral and written expression, and autonomous learning in children through the creation of characters and the adaptive narration of stories.

3. Specific Objectives

• To design the physical and mechanical structure of the puppet, incorporating a motion control system based on a four-bar linkage mechanism.
• To integrate an audio synchronization system that enables the puppet to move its mouth coherently with voice recordings narrated by users.
• To develop a mobile application that facilitates story uploading, puppet control, and narrative content customization.
• To implement a modular physical customization system that allows users to modify the puppet’s eyes, mouth, nose, and hair to create unique characters.
• To evaluate the usability, portability, and efficiency of the system in educational environments through pilot testing with child users.
• To promote the strengthening of children's creative, narrative, expressive, and technological competencies through the use of the puppet in educational and recreational activities.

4. Justification

Puppets have been used for centuries as educational and entertainment tools. However, most require manual manipulation, limiting immersion in the story. This project seeks to create an interactive puppet that enhances the storytelling experience, offering a more dynamic and immersive way to tell stories.

The proposal to develop a customizable interactive puppet responds to the current need to integrate emerging technologies into creative and expressive learning processes for children. In an educational context that demands innovative approaches to foster creativity, autonomy, and narrative thinking, this project offers a solution that combines precision mechanics, audio synchronization, mobile connectivity, and modular design.

The use of a puppet as an educational tool has strong pedagogical foundations, as it facilitates oral expression, stimulates imagination, strengthens social skills, and motivates the construction of personal narratives. However, by incorporating interactive technologies—such as voice-synchronized motion control and character customization through mobile devices—this project elevates the traditional potential of puppetry to a level aligned with 21st-century competencies.

4.1. Multidimensional Impact

• In the educational field: Contributes to the development of oral and written communication skills, narrative creativity, and early digital literacy.
• In the technological field: Promotes children's engagement with basic programming concepts, simple robotics, and mechanical design, all through play and direct interaction.
• In the social field: Fosters inclusion and active participation for all children, regardless of their abilities or backgrounds, through intuitive and accessible tools.

Additionally, the possibility for children to create and document their own stories strengthens meaningful learning processes and opens the door to the creation of original content, encouraging innovation, children's entrepreneurship, and critical thinking.

Finally, the project offers practical advantages such as the device’s portability, its adaptability to various contexts (school, home, therapeutic), and its future scalability through the incorporation of new movement modules, which extends its useful life and applicability.

For all these reasons, this project not only addresses a current educational need but also projects a sustainable and innovative proposal aligned with global trends in creative education and educational technology.

5. Methodology

Stage 1: Definition

The equipment specifications are established, including technical requirements and constraints.

Stage 2: Conceptual Design

Solution principles and the basic design structure are developed.

Stage 3: Materialization Design

General drawings are created, and prototypes are built to validate the concept.

Stage 4: Detailed Design

Manufacturing plans and part specifications are prepared for production.

5.1 Definition - Product Specifications

Product Objective: Develop an interactive sponge puppet that synchronizes facial movements with storytelling narration, enhancing children's storytelling experiences.

Functional Requirements

• Mouth and facial expressions synchronized with the narrator’s voice.
• Real-time response to audio signals.
• Simple user interface for control and configuration.

Non-Functional Requirements

• Use of safe and durable materials suitable for children.
• Minimum autonomy of 2 hours of continuous use.
• Ergonomic and visually appealing design for children.

Constraints

• Maximum budget of $700.
• Compliance with toy safety regulations.
• Size and weight limitations for easy handling.

Specification Table

5.2 Conceptual Design

Based on the specifications, multiple concepts are generated to meet the established requirements. Each concept is evaluated considering factors such as technical feasibility, cost, ease of manufacturing, and user experience. Tools such as function diagrams, sketches, and preliminary models are used to visualize and communicate ideas.

5.2.1. Optimal Concept Selection

A decision matrix is used to compare the different concepts developed in the previous phase. Criteria considered include:

• Compliance with functional and non-functional requirements.
• Estimated production cost.
• Ease of assembly and maintenance.
• Potential user acceptance.

The conceptual design of the customizable interactive puppet combines mechanical engineering, electronics, and artistic design to create a powerful educational and creative tool for children. The system is based on a simple yet highly effective mechanical structure, synchronized with audio signals and controlled via a mobile application.

5.2.2. Internal Structure and Mechanism Overview

The first image shows the internal mechanism of the puppet's head, where several critical components are highlighted:

• Four-Bar Linkage Mechanism: A mechanical system responsible for moving the puppet's mouth, allowing it to open and close smoothly.
• Motor Connection: A motor connected to the linkage supplies the motion needed for mouth movement.
• Audio and Bluetooth Electronics: Audio processing and wireless control via a mobile app.
• Power Supply: A rechargeable battery ensures portability and independence from external power.

Summary: This design ensures a lightweight, portable puppet that realistically simulates mouth movement according to the uploaded narration.

5.2.3. Puppet Front and Side Views

In the second image, two essential views are presented:

• Front View: Displays the customizable puppet’s face for creative adaptations.
• Side View (with Mechanism): Shows the linkage system transmitting motor rotation into mouth movements.

Summary: The separation of design and mechanics allows easy character customization without affecting functionality.

5.2.4. Technical Plan and Cross-Section Drawings

The third image provides technical plans and sectional diagrams:

• Side and Cross-Section of the Casing: Shows the compact, protective enclosure of the system.
• Motor and Linkage Mounting: Details the structural support for stable motion control.
• Guides and Supports for Moving Parts: Ensures smooth, low-friction, and durable operation.

Summary: The technical structure guarantees mechanical integrity, supporting frequent and reliable educational use.

5.2.5. Conclusion of conceptual design

The conceptual design of the customizable interactive puppet provides:

• Efficient mechanical operation via a four-bar linkage system.
• Real-time audio synchronization for realistic animations.
• Creative flexibility through character customization.
• Portability and usability for educational and recreational environments.
• Future scalability for adding new movement modules like eyes and hands.

This robust design ensures a highly engaging and educational platform for children, promoting creativity, storytelling, and technological interaction.

5.3 Materialization Design.

Mechanical Design

• 3D modeling of the puppet's internal and external structure.
• Specification of materials and mechanical components, including servo motors and transmission mechanisms.
• Tolerance and adjustment analysis to ensure optimal functionality.

Mechanical System Integration – Mechanical Design

This section documents the conceptual mechanical design of the puppet's head movement system. The structure was modeled in SolidWorks and integrates a physical support, servo-driven mechanisms, and a rotating jaw.

1. Structural Frame

The orange L-shaped frame provides a stable base to mount all components. It ensures rigidity and alignment between the servos and the puppet's head. All parts are designed for easy assembly using bolts or press-fit systems.

2. Internal Components and Transparency View

In the following view, the puppet’s head is shown semi-transparent, revealing the internal servo motors, pivots, and transmission rods that control jaw movement. The main servo (MG996R) is mounted on the back and pushes a printed lever connected to the lower jaw.

3. Side View of Mechanical Motion

The side perspective shows the angular motion path of the jaw. The linkage system was dimensioned to allow natural-looking mouth movement with minimal force.

4. Functional Kinematics

The next view shows how each part is kinematically constrained. The arm of the servo rotates and transmits the force through a direct mechanical linkage. No springs or elastic return mechanisms are used; instead, passive motion is governed by the servo’s torque and calibrated endpoints.

5. Prototype Motion Video

The video below shows the movement of the assembled prototype. You can observe the servo moving the jaw using the mechanical transmission inside the puppet's head.

Conclusion

The mechanical subsystem is a compact, functional unit that allows natural articulation of the puppet’s jaw using servo actuation. Its integration with the structural frame and 3D-printed elements enables fast prototyping and easy testing of expressive movements. This design will be used in combination with textile and electronic subsystems as part of the final puppet system.

Electronic System – Audio-Based Control Integration

The electronic system developed for the puppet enables voice-activated control of movement using a microphone, an analog amplifier, and a custom microcontroller board. This subsystem captures sound signals, amplifies them, and processes the signal to trigger movements in the mechanical subsystem.

To create the custom PCB used in the final project, a Roland SRM-20 milling machine was used. The workflow included the generation of toolpaths using FlatCAM and controlling the mill with VPanel software.

Once the G-code was prepared and uploaded, the board was milled on a copper-clad substrate. The traces and pads were defined with precision milling to create clean electrical connections.

After milling, the electronic components were soldered onto the board. The assembled circuit includes capacitors, resistors, a microphone module, transistors, and an LM358 op-amp, among other elements, forming a complete analog front-end for sound detection.

1. Signal Conditioning Circuit

The following schematic shows the preamplifier circuit based on the LM358 operational amplifier. It receives the audio signal from a microphone and applies a gain defined by resistor R2. Capacitor C1 acts as a coupling stage, while R3 and R4 form a voltage divider to bias the non-inverting input. The output is DC-decoupled by C2 and sent to the microcontroller for processing.

2. Actuation Interface

The amplifier output feeds into a PCB designed to detect audio peaks. This board, shown below, was milled and soldered in-house. It uses an ATtiny microcontroller programmed to read analog signals and produce a PWM output when sound intensity exceeds a threshold. The PWM signal drives a servo motor responsible for animating the puppet’s jaw.

3. Servo Integration Test

The next image shows the prototype setup with the servo mounted to a laser-cut wooden base. The system receives the PWM signal generated by the microcontroller and translates it into a jaw movement. The linkage is calibrated to respond proportionally to sound intensity.

4. Integrated Functionality – Video Demonstration

In the videos below, the entire system is demonstrated. A sound (such as a voice or a clap) is captured by the microphone, amplified by the LM358 circuit, and processed by the custom PCB. This results in a corresponding motion from the servo, visually demonstrating the mouth opening of the puppet.

Audio-Driven Servo Control – Arduino Code Explanation

The following code allows a puppet to move its mouth in response to ambient sound. It reads analog values from a microphone connected to pin A0 and controls a servo motor on pin 9 based on the detected volume level.

Code Overview

						
#include 
Servo miServo;
int pinServo = 9;
int soundPin = A0;
float data_ant=0;
float data=0;
float data_Act=0;
float k;


const int micPin = A0;
float env = 0.0;
const float alpha = 0.1; // Constante de suavizado
// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 19000 bits per second:
  Serial.begin(19200);
  miServo.attach(pinServo);
}

// the loop routine runs over and over again forever:
void loop() {
int raw = analogRead(micPin);
  int centered = raw - 570;
  float absSignal = abs(centered);
  env = alpha * absSignal + (1 - alpha) * env;

Serial.print("Envolvente: ");
Serial.println(10*env);
miServo.write(env);                 
delayMicroseconds(100);
}

How It Works

• Microphone Input: The analog pin A0 is used to read voltage variations from an electret microphone, which represents incoming sound signals.
• Centering the Signal: The microphone typically has a DC bias (~570). Subtracting this bias centers the signal around 0, making it easier to calculate its envelope.
• Envelope Detection: The code computes the envelope (or volume level) using an exponential smoothing filter:
  env = alpha * abs(centered) + (1 - alpha) * env;
  This equation smooths out rapid fluctuations and tracks the general loudness of the sound.
• Servo Control: The computed envelope is then written to the servo motor using miServo.write(env). This moves the servo arm in proportion to sound intensity, producing a mouth-like motion in sync with speech or claps.
• Serial Monitor Output: The value of the envelope (scaled by 10) is printed to the serial monitor to help visualize sound levels and debug the system.

Purpose in the Puppet Project

This script forms the core of the puppet's interactive behavior. By converting real-time audio into mechanical motion, it enables the puppet to mimic human-like mouth movements. The result is a reactive, expressive character that appears to "talk" based on environmental sound cues.

Conclusion

This electronic subsystem enables interactive control of the puppet using environmental audio. The analog front-end (amplifier) and digital signal detection circuit were designed, tested, and integrated with the mechanical components. This modular design allows future improvements such as distinguishing between voice types, intensities, or using wireless control inputs.

Fabrication Process

1. Laser-cutting of chassis

2. 3D-printed mechanical parts

Parts printed with Bambu Lab X1-Carbon, designed to be lightweight and structurally precise for mouth motion.

3. Servo motor mounting and integration

Final Integration and Prototype Testing

These images show the minimum viable prototype (MVP) fully assembled. The jaw mechanism is tested and reacts to control signals through the servo motor.

5.4 Detail Design.

The Detail Design is the final phase in the development process of a product, system, or engineering project. In this stage, all the necessary elements for the manufacturing, assembly, implementation, or construction of the final product are precisely defined.

This methodology, inspired by Concurrent Engineering and Integrated Product Development approaches, ensures that all disciplines work in a coordinated manner from the initial stages of the project, minimizing rework and optimizing the development process of the "Sponge Puppet with Mechanism for Storytelling".

Final Project Results – Interactive Puppet

The final prototype is a fully functional interactive puppet capable of responding to environmental sounds such as speech or claps. The system integrates 3D-printed mechanical parts, a voice-activated control circuit, and a programmed microcontroller that drives the jaw movement through a servo motor.

1. Assembly and Mechanical Behavior

The images below show the puppet in its final assembled form. The head is composed of two 3D-printed hemispheres, where the lower section acts as a movable jaw. It is mounted on a wooden support structure that holds the servo in place.

2. Character Design

A playful facial expression was added using white 3D-printed eyes and mouth parts, giving the puppet a more friendly and expressive appearance. The face was designed to align precisely with the moving jaw for a natural animation.

3. System Integration and Real-Time Performance

Below is a video showing the puppet in operation. When a sound is detected by the microphone, the amplifier circuit processes the signal, the microcontroller calculates the envelope, and the servo responds by opening the puppet’s mouth. This real-time interaction gives the appearance that the puppet is talking or reacting to its environment.

4. Conclusion

The result is a working electromechanical puppet that responds to sound stimuli, demonstrating successful integration of mechanical design, electronics, and embedded programming. The system is modular and extensible, allowing further development such as speech synthesis, animation synchronization, or interaction with mobile apps.

Final Assembly Status – Puppet Completion and Integration

The interactive puppet is now in its final integration phase. The mechanical and electronic systems are fully functional, and the final structural pieces have been assembled. At this stage, the project is focused on installing the final control boards, polishing cosmetic finishes, and validating the overall system performance for presentation and deployment.

1. Puppet Face and Costume – Final Touches

The puppet’s visual details were finished by hand, including mouth painting, ear shaping, and the integration of expressive facial lines. The red cape complements the overall design, creating a coherent theatrical appearance.

The puppet head, crafted with foam and fabric, is mounted on the vertical wooden support. Beneath the puppet's cape, the electronic circuit responsible for mouth movement and audio response is discreetly housed. This design ensures both functional integration and aesthetic concealment.

Removing the cape reveals the custom-built PCB installed on a wooden base. The circuit includes components for signal amplification, filtering, and motor control, allowing the puppet's mouth to react in sync with audio inputs.

2. Structural Assembly and Exploded View

The base structure was developed with interlocking wooden panels. Below is a technical exploded view that details the arrangement and quantity of each piece, servo placement, and anchoring zones. This helps ensure reproducibility and maintainability.

The puppet system is mounted on a laser-cut wooden stand. The vertical design provides stability and visibility, ideal for integrating mechanical motion from servos while maintaining the puppet at an ergonomic height for performance.

The rear view shows the placement of the servo motor, which controls the puppet's mouth motion. The structure was designed to be modular and easy to assemble using interlocking joints.

3. Finished Puppet with Expressive Design

The puppet now features a fully stylized appearance, including orange sponge material for facial texture, synthetic blue hair, and a red satin cape. These elements provide a playful and character-driven visual identity.

4. Scanning for Digital Documentation

A 3D scan was performed using professional scanning equipment. The result was processed and visualized in software for digital archiving, replication, and potential further enhancements.

5. Interactive Puppet Operation

The interactive puppet operates through the integration of a microcontroller that coordinates audio playback and servo motor movement, allowing the character's mouth to synchronize with the storytelling. The system includes a sound module with a speaker, a hidden structural base that houses the electronics, and an interchangeable mask mechanism that makes it easy to switch characters depending on the story. During operation, the puppet creates an immersive and expressive experience for the audience, especially in educational settings. While the current performance is satisfactory, adjustments to the audio-motion synchronization and additional testing are needed to ensure system stability and durability over extended use.

This test was carried out to verify that the puppet can move its mouth in sync with the narrator’s voice. A microphone with amplifier was used to detect the voice signal, which is processed by a microcontroller that activates a servo motor controlling the mouth movement.

Conclusion

The result is a robust, expressive, and modular puppet prototype that fulfills all the functional and aesthetic goals set at the beginning of the project. With only the installation of the final electronics and decorative enhancements remaining, the puppet is ready for public presentation, educational demonstrations, and future iterations.

Packaging and Product Finish

The prototype is designed as a modular, maintainable system. The final packaging will include casing for electronics, removable face modules, and wireless control. It has been crafted to reflect a product-oriented approach suitable for educational contexts.

6. Expected Impact

• Improvement in storytelling experiences.
• Increased attention and interaction from children.
• Use of accessible technologies for education and entertainment.