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Automated Litter System

Electrical Architecture & Embedded Intelligence

Course Instructor: Dr. Remon Pop-Iliev

Project Supervisor: Dr. Murat Aydin

Group Number: 21-2-5

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Problem Statement

Cat owners face ongoing issues with litter box maintenance, including frequent cleaning, odor buildup, and inconsistent hygiene, which impact both convenience and home cleanliness.

Existing Solutions

Automated products such as Litter‑Robot and CatGenie reduce manual scooping but are often:

Expensive
Noisy during operation
Complex to clean and maintain

Identified Gap

Current systems do not fully address key user needs, particularly in:

Safety and reliable cat detection
Quiet operation
Ease of cleaning and maintenance
Affordability and long‑term sustainability

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Mechanical Design & Engineering Innovation

Designing for Serviceability, and Reliability

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Design Overview

Modern aesthetics meet reliable engineering a design

that looks good and performs flawlessly.

A rotating drum mechanism that sifts, separates, and disposes of waste automatically.

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Mechanical Overview

Fastener-Free Maintenance: The Entire unit can be fully disassembled for cleaning and reassembled without a using tools.

Key Features: Fit in place top cover,simply-supported drum, and a slide-out litter sifter and waste tray.

Ease of Access: The drum module lifts directly out, and the gear drive remains in the base, eliminating complex disassembly steps.

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CAT-FRIENDLY DESIGN & ERGONOMICS

Spacious Interior:

Provides ample headroom for cats to stand, turn around, and assume their natural postures

Generous Floor Area:

Allows for comfortable movement and digging.

Accessible Entry:

A wide 30 cm entrance offers easy,unobstructed access for the cat.

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Prototyping Challenges

Putting our design to the test

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Scale & Geometry

Scale: 50% of full design size (printer bed limitation)

Challenge 1 – Build Volume: The full Drum and Base assembly maximum dimension (30cm) exceeded our printer's maximum dimensions.(22cm)

Solution: The drum and base components were sliced into multiple parts directly in SolidWorks prior to exporting for printing.

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Gear Selection

Due to the reduced 50% scale, the original spur gear design could no longer fit within the available space, requiring a complete reevaluation of the drivetrain.

Attempt	Gear Type	Outcome
1	Spur Gear + Face gear	Difficult alignment; drum rotation was erratic, shaky, and clunky
2	Bevel Gear	Complex alignment, space still insufficient
3	Helical Gear	Reduced noise & axial load for stability

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Gear Selection

Result: The final design utilizes a miter gear pair to transfer rotation 90 degrees, followed by a helical gear stage to drive the drum. This compact, two-stage gearbox fit within the reduced envelope while delivering smooth, quiet, and stable operation.

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Manufacturing

Manufacturing for Serviceability, and Reliability

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Prototyping

Prototype 3D Printing

Rapid design and development

Quick CAD design to physical parts
Faster for testing and optimization

Cost effectiveness

Eliminates budget-consuming molds and casts
Inexpensive materials and equipment

Reduced Risk

Discover flaws at early stage and fine-tune parts

For this project, we focused on developing a functional prototype using 3D printing.

We selected 3D printing because it supports rapid design and development. It allowed us to quickly convert our CAD models into physical components, making it easier to test the fit, functionality, and overall system performance. This was especially useful for the rotating drum and internal mechanisms.

From a cost perspective, 3D printing is well-suited because it eliminates the need for expensive moulds and tooling. It also uses relatively low-cost materials, which gave leeway to design multiple iterations within a limited budget.

Additionally, it helps reduce risk. By building and testing physical prototypes early, we were able to identify design issues, refine component alignment, and improve overall system reliability.

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Durability

Impact resistances due to higher yield and tensile strength
less susceptible to heat

Production

Ease of processing

Low melt viscosity
Better texture and feel for the end users

Recyclability

Remoldable and recyclable
Reduced manufacturing waste

ABS Mold Injection

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Power, Electrical & Sensor Integration

Design, Wiring, and System Validation.

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Electrical System Architecture

ESP-32 ● Sensors ● Signal Processing ● Motor Control

Real-time sensor integration and control system

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Sensor Output (Serial Monitor)

Sensor Testing & Validation

Sensor	Function	Results
Load Cell	Presence detection	✔ Accurate
Hall-Effect	Position tracking	✔ Reliable
ACS-712 Current	Current monitoring	✔ Stable readings

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Motor & Camera Validation

Sensor	Function	Results
Motor	Drum rotation	✔ Stable operation
Camera	Object detection	✔ Accurate detection

Sensor Output (Serial Monitor)

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Power & Electrical Layout

Designing for stability, high torque, and domain isolation.

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24V SRPM DC Worm Gear Motor

Main Power Loop

Powered by an industrial 24V supply to ensure maximum torque for heavy waste separation.

BTS7960 Driver

High-current H-bridge handling 43A peak current.

EACS712 Current Sensor

Monitors motor load for stall detection and safety stop.

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24V → 5V

Buck Regulation Step

High-Efficiency Power Conversion

DUAL-STAGE VOLTAGE REGULATION

To support the low-power logic components, a high-efficiency Buck Converter steps down the primary 24V supply to a stable 5V rail.

ESP32 & Raspberry Pi 4 Microcontroller Stable 5V logic supply.

OpenMV Vision System 5v Powering image processing camera

Sensor Array Precise 5v for load cells and Hall sensors.

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Fuse Protection

Reverse Polarity

Emergency Stop

PROTECTION & SAFETY LAYER

Dedicated overcurrent protection prevents component failure during mechanical jams.

Design-level protection against incorrect power connection during maintenance.

Design-level safety integration allowing for immediate system power-down.

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Sensor Fusion & Intelligence

Implementing state-based logic for predictable and safe operation.

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IDLE

WEIGHT PRESENT

EXIT DELAY

CLEANING

HOMING

STATE-BASED CONTROL SYSTEM

Monitoring sensors for presence

Load cell confirms weight entry

Wait for safety timer completion

Drum rotation and separation

Return to precise start position

Load cell confirms weight entry

CAMERA ENTRY AND EXIT DETECTION

DUAL SENSOR CONFORMATION

Signal confirmation on cat present or not

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OpenMV Camera

Load Cell Sensor

DUAL-SENSOR VALIDATION LOGIC

Cleaning is only triggered when both sensors confirm absence following an entry event.

Motion detection at the entry point provides the first trigger for the "Cat Present" state.

Weight-based confirmation ensures a cat is actually inside, preventing false triggers from outside movement.

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PRECISION CLEANING & HOMING

Forward Cycle Controlled rotation for litter separation phase (cleaning phase).

Reverse Cycle Drum return cycle to level the clean litter.

Hall Effect Homing Final homing using magnetic sensors for sub-millimeter positional feedback.

UART Communication Real-time event-driven link between OpenMV and ESP32 controller.

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SAFETY INTELLIGENCE

Safety is the primary design pillar. The "Exit Validation Logic" ensures the drum never rotates while a cat is present.

Delay Timer Only starts after motion stops and weight returns to baseline.

Operation Blocking Cleaning is hard-blocked if load cell detects residual weight.

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Prototype Video