Week 16: System Integration
Assignment: Design and document the system integration for your final project
Project Contextualization
Traditional piggy banks introduce the habit of saving, but they are fundamentally passive objects. Money is dropped into a container with little awareness of the amount being saved, the purpose behind it, or progress toward a specific goal. While effective as a simple storage device, they offer limited engagement and provide no structured feedback that supports financial learning.
Penny Pal reimagines the piggy bank as an interactive educational product designed to promote goal-based saving. Instead of simply collecting coins, the system encourages children to actively identify each coin denomination before it is accepted. This deliberate interaction transforms saving from an automatic action into a conscious decision-making process.
The project combines physical and digital elements to create a more engaging saving experience. A companion mobile application allows parents to define savings goals and monitor progress remotely. The piggy bank responds to each deposit with audio and visual feedback, acknowledges milestones, and unlocks only when the savings goal has been achieved.
At a technical level, Penny Pal integrates:
The project sits at the intersection of product design, embedded electronics, digital fabrication, and interaction design. It explores how a familiar object can be transformed into a tangible learning tool that supports behavioral development through feedback, participation, and reward.
By combining active participation with goal tracking and positive reinforcement, Penny Pal aims to make saving more intentional, motivating, and educational for children.
Penny Pal - Final Project Development Plan
User Flow Diagram
Functionality Diagram
The Interaction Flow
0. Set the Goal: Before saving begins, the parent sets a savings goal through the companion app. The goal is sent to Penny Pal via Wi-Fi, and the piggy bank locks.
1. Wait: The system remains idle while the IR sensor continuously monitors the coin slot.
2. Detect: A coin is inserted. The IR beam is interrupted and the system detects the coin.
3. Prompt: A greeting sound and visual cue indicate that a coin is waiting and a denomination must be selected.
4. Identify: The child observes the coin and recognizes its denomination.
5. Decide & Confirm: The child presses the corresponding denomination button.
6. Accept: The flap opens, the coin drops into the chamber, and the flap closes.
7. Acknowledge: The system updates the savings total and responds with sound and light feedback.
8. Celebrate: At 25%, 50%, 75%, and 100% progress, milestone feedback is triggered.
9. Return: The system returns to idle and waits for the next coin.
10. Goal Achieved!: When the goal is reached, the piggy bank celebrates, unlocks, and the child retrieves the savings.
Algorithm Diagram
Piggy Bank Form Exploration
During the enclosure development phase, I collected a wide range of piggy bank references from online marketplaces, design communities, and social media. The intent was not to replicate any specific form, but to understand how broadly the piggy bank archetype has been interpreted across different cultures, materials, and design styles.
The references range from:
This exercise reinforced an important observation: the visual language of a piggy bank is highly flexible. There is no single “correct” form. As long as a few recognizable cues are retained, such as the snout, ears, and coin slot, the object remains immediately identifiable.
For Penny Pal, this insight was useful because it shifted the design focus away from finding a perfect external form and toward resolving the internal mechanism and user interaction. The enclosure serves as a carrier for the functional system rather than the primary innovation.
At the same time, this exploration provided confidence that the final form can be developed with significant creative freedom while still preserving the familiarity and emotional appeal associated with the piggy bank archetype.
Design Intent
The final enclosure aims to:
In this sense, the reference board functions as a reminder that while the internal mechanism defines the product’s novelty, the external form remains open to interpretation. A piggy bank can take many visual expressions; what matters is that the design supports the intended interaction and meaning.
Initial Layout and Packaging Concept
Concept sketch showing the internal layout and approximate dimensions of the Smart Piggy prototype. The enclosure is based on a simplified pig silhouette measuring roughly 16 × 16 cm. A coin is inserted through the slot at the top, where an IR sensor detects its presence and a servo-actuated gate controls whether it is accepted. Once approved, the coin drops through an internal channel into the central storage chamber. Electronics, including the custom PCB and battery, are positioned around the perimeter and within the base to keep the coin compartment unobstructed. This sketch was used to evaluate spatial relationships between the mechanical components, electronics, and storage volume before developing the final CAD model.
A quick proof-of-concept prototype built from paper to test the coin detection and sorting mechanism. The assembly integrates a coin chute, IR sensor, and servo-actuated flap to verify that coins can be reliably detected and redirected before entering the storage chamber. This physical mockup was used to evaluate component placement, coin clearance, and mechanical behavior prior to designing the final integrated enclosure.
A simplified CAD model developed in Fusion 360 to translate the proof-of-concept mechanism into a manufacturable design. The model defines the relationship between the coin chute, sensor mount, actuator housing, and storage compartment, allowing key dimensions and clearances to be evaluated before integrating the mechanism into the final pig-shaped enclosure.
A series of CAD iterations on Fusion exploring how all the internal components fit within the pig-shaped enclosure. The initial model focused on defining the overall form, along with the coin slot and snout opening for the speaker. Section views were then used to work out the placement of the coin chute, IR sensor, solenoid, coin chamber, battery, and custom PCB. I am also planning on using transparent acrylic side panels for the coin chamber so the saved coins remain visible, along with a bottom access hatch to make it easier to assemble and service the electronics. These models helped me check clearances, refine the internal layout, and confirm that the overall design is feasible but I need to verify and remake certain parts before working on the final model.
Based on the enclosure strategy I have developed so far, the product is designed as a two-part assembly consisting of an outer shell and a functional base.
Outer Shell
The top part acts as a helmet-like cover that fits over the internal structure, enclosing and protecting the electronics and mechanisms while giving the product its final character and form. This shell integrates all of the user-facing features, including the coin slot, button interfaces, and the snout, which also serves as the speaker opening.
Functional Base
The bottom part serves as the primary structural housing for all internal components. The upper side contains the coin chamber and coin chute, along with mounting locations for the button breakout board, IR sensor, NeoPixel LEDs, and actuators such as servos or solenoids. The underside is reserved for the main PCB and battery, housed in a dedicated compartment that can be accessed through a detachable bottom panel.
This split construction allows the internal systems to be assembled and tested independently before the outer shell is placed over them, simplifying both prototyping and maintenance.
Electronics block diagram
Block Diagram
KiCAD Schematic (work in progress)
