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2 layersSmartBin, the printed circuit board in 3D

Automated Organic Waste Processor

Copper layers
2
Thickness
1.6 mm
Parts
13
Nets
37
Pads
100
Tracks, vias
0, 0
Routed
Not yet
KiCad
KiCad 9.0 (file 20241229)
Created
12 Feb 2026
Updated
13 Feb 2026

Overview

SmartBin is an open-source printed circuit board by ola-oye, from the ola-oye/SmartBin repository on GitHub. It is a 2-layer board with 13 parts on 37 nets.

It is built around the HLK-20M12, DS18B20 and L7805CV. Its parts include 7 connectors, 2 capacitors, 2 ICs and 1 resistor.

Main components

3

README

README.md

SmartBin - Automated Organic Waste Processor

Overview

SmartBin is an automated system that converts organic waste into compost through a controlled drying and grinding process. The system features odor control using carbon filtration, automated waste level detection, and a custom-designed ESP32-based motherboard for complete process automation.

Key Features:

  • Automated waste level monitoring using ultrasonic sensors
  • Odor control system with carbon filter and exhaust fan
  • Controlled drying via 50W heating element
  • Automated grinding using 120W AC blender motor with PWM speed control
  • Custom PCB design with high/low-voltage isolation
  • FreeRTOS-based task management

System Architecture

System Block Diagram

System Schematic

Process Flow:

  1. Waste Collection → Ultrasonic sensor monitors fill level
  2. Odor Filtration → Fan pulls air through carbon filter before exhaust
  3. Drying Stage → Heating element activates at threshold level
  4. Grinding Stage → AC motor pulverizes dried waste
  5. Storage → Processed compost collected in separate compartment

Hardware Design

Custom Motherboard (KiCad)

PCB Front View Top layer of SmartBin control board

PCB Back View Bottom layer showing power traces and isolation

Board Specifications:

  • Controller: ESP32-WROOM-32
  • Power Input: 220V AC mains
  • AC Loads: 120W blender motor, 50W heating element
  • DC Loads: 5V fan, 3.3V control logic
  • Protection: Fuse, optoisolators, flyback diodes
  • PCB Layers: 2-layer, FR4
  • Dimensions: [Add dimensions in mm]

Key Components:

ComponentPurposeInterface
ESP32Main controller-
HC-SR04Waste level detectionGPIO
TRIAC + OptocouplerAC motor speed controlPWM
Solid State RelayHeating element controlGPIO
12V/5V RegulatorsDC power supply-
Current SensorMotor load monitoringADC

Power Distribution:

text
220V AC ─┬─► AC Motor (via TRIAC dimmer)
         ├─► 50W Heater (via SSR)
         └─► AC-DC Converter ──► 12V ──► 5V ──► 3.3V ESP32
                                      ├─► Fan
                                      └─► Sensors

Hardware Setup:

  1. Fabricate PCB: Upload Gerber files to JLCPCB
  2. Solder Components: Follow assembly drawing
  3. Connect Sensors: Wire ultrasonic sensor to designated headers
  4. Power Connections: 220V AC input via terminal block
  5. Motor Connection: AC motor to TRIAC output
  6. Heater Connection: Heating element to SSR output

Testing & Validation

TestMethodResult
Motor speed controlOscilloscope (PWM waveform)±5% accuracy
Temperature regulationThermocouple logging±2°C
Level detectionManual measurement vs sensor±2mm
Power consumptionAC power meter125W max
Cycle timeFull dry → grind cycle45-60 min

Challenges & Solutions

ChallengeSolution
AC motor EMI interfering with ESP32Added optoisolation, separate ground planes
Heating element overshootImplemented PID control instead of bang-bang
Moisture damage to electronicsEnclosed PCB in sealed compartment
Inrush current on motor startAdded soft-start PWM ramp

Future Improvements

  • WiFi connectivity for remote monitoring
  • Mobile app integration for status alerts
  • Solar power compatibility
  • Automatic compost quality sensing
  • Multiple bin capacity expansion
  • Machine learning for optimal cycle prediction

Author

Fatai Oyetunji
Computer Science, University of Lagos
GitHub | LinkedIn


Acknowledgments

  • University of Lagos Computer Science Department
  • NitHub, University of Lagos
  • Project supervisor and team members
  • Open-source KiCad and ESP32 communities

⭐ If you found this project useful, consider giving it a star!

Parts

13
QtyValueFootprintReferences
2Conn_01x19_SocketConnector_PinSocket_2.54mm:PinSocket_1x19_P2.54mm_VerticalJ5, J6
2Screw_Terminal_01x19TerminalBlock:TerminalBlock_MaiXu_MX126-5.0-19P_1x19_P5.00mmJ4, J7
10.1ufCapacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolderC3
10.33ufCapacitor_SMD:C_0402_1005Metric_Pad0.74x0.62mm_HandSolderC4
14.7knResistor_SMD:R_0402_1005Metric_Pad0.72x0.64mm_HandSolderR1
1AC-INTerminalBlock:TerminalBlock_MaiXu_MX126-5.0-02P_1x02_P5.00mmJ1
1DS18B20Package_TO_SOT_THT:TO-92_InlineU2
1HLK-20M12HLK-20M12:CONV_HLK-20M12PS1
1L7805CVL7805CV:TO255P1040X460X1968-3U1
1Screw_Terminal_01x02TerminalBlock:TerminalBlock_MaiXu_MX126-5.0-02P_1x02_P5.00mmJ2
1Screw_Terminal_01x04TerminalBlock:TerminalBlock_MaiXu_MX126-5.0-04P_1x04_P5.00mmJ3

Questions

What parts does the SmartBin use?

13 parts, built around the HLK-20M12, DS18B20 and L7805CV. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the SmartBin KiCad files?

From the ola-oye/SmartBin repository on GitHub, at the commit this page was made from: the board is smartBin/smartBin.kicad_pcb and its schematic smartBin/smartBin.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the SmartBin design in my own project?

Its repository states no licence, so its author keeps all rights: ask ola-oye before reusing the design.

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