Case Study · Hardware · Machine Learning · Published Research

Smart Trash Sorting Device

A camera-based garbage bin that sorts recyclable from non-recyclable waste on its own — image processing and machine learning replace the unreliable sensors most smart bins rely on. Published at ICMIME 2024.

Role
Lead Author & Builder
Timeline
2024
Domain
Computer Vision · Embedded Systems
Published
ICMIME 2024, RUET
Overview

Where it started

Most "smart bin" research sorts waste using sensors — moisture, capacitive, metal — which are fragile and prone to failure from dust, heat, and noise, and few of them target the specific problem of recyclable vs. non-recyclable waste.

We built the alternative: a camera and a trained machine learning model doing the sorting instead of a sensor guessing at it, with a servo motor acting on the result. Built with a team of RUET engineering classmates and published as peer-reviewed research at ICMIME 2024.

The problem

Sensors guess. A camera can look.

Before · typical smart bins

  • Sensor-based sorting (moisture, capacitive, metal) — fragile, environment-sensitive
  • Usually splits waste into wet/dry, not recyclable/non-recyclable
  • Manual sorting still required for proper recycling
  • Low reliability from dust, heat, and electrical noise

After · this device

  • A camera + trained ML model reads what the object actually is
  • Classifies specifically as recyclable or non-recyclable
  • A servo motor acts on the result automatically — no manual sorting
  • Real-time processing, ~90% classification accuracy in testing
How it works

From detection to disposal

Capture
Push-button start
ESP32-CAM detects & photographs the item
→
Process
Computer vision extracts the object from the image
→
Classify
Pre-trained ML model
Recyclable / Non-recyclable
→
Act
Servo: anticlockwise (recyclable) / clockwise (non-recyclable)
Item drops into the correct bin
No sensors in the classification loop — the decision comes entirely from the image
The build

Order of operations

1
Power on
Push button starts the device; servo does an initial calibration sweep.
2
Detect
An item placed in front of the bin triggers the ESP32-CAM.
3
Capture
The camera takes a real-time image of the item.
4
Process
Computer vision techniques identify the object in the frame.
5
Classify
The pre-trained ML model scores it recyclable or non-recyclable.
6
Decide & sort
The servo motor rotates to route the item to the matching bin.
7
Dispose
The item drops in automatically; the bin is ready for the next item.
Features

What the device does

01 · Vision

Camera-based sorting

ESP32-CAM captures and streams real-time images.

02 · Classification

ML classification

A model trained on recyclable/non-recyclable product images makes the call.

03 · Mechanism

Automatic servo sorting

Anticlockwise for recyclable, clockwise for non-recyclable.

04 · Design

No sensor dependency

Avoids the fragility of moisture/capacitive/metal sensors.

05 · Performance

Real-time processing

Minimal delay from detection to disposal.

06 · Fabrication

Built from scratch

ESP32-CAM, FTDI programming, a Vero-board circuit, and a PVC-housed dual-bin enclosure.

Results

What testing showed

In testing, the system classified waste as recyclable or non-recyclable with ~90% accuracy, processing images in real time with minimal delay. The servo motor reliably routed items to the correct bin without human intervention, cutting contamination between waste streams.

Accuracy dropped in low-light conditions, and scaling to more varied urban waste profiles would need a larger training set — both noted as directions for future work.

Stack

Built from board-level parts

ESP32-CAM
Image capture, Wi-Fi/Bluetooth, dual-core processing
ML model
Pre-trained image classifier (recyclable / non-recyclable)
Computer vision
Image processing pipeline ahead of classification
Servo motor
Mechanical sorting action
FTDI Uploader
Firmware flashing
Vero board
Prototyping circuit
PVC board + dustbins
Physical housing and sorted receptacles
Impact

A camera, doing what sensors couldn't

~90% classification accuracy in testing, recyclable vs. non-recyclable.
Real-time image processing with minimal delay.
Fully automatic sorting — no human intervention needed at disposal.
Reduces contamination between recyclable and non-recyclable streams.
Published and peer-reviewed at ICMIME 2024.
Noted limitations: accuracy drops in low light, and broader deployment would need a larger, more diverse training dataset — both flagged as future work in the paper.
More case studies

More work

See the rest of the work.