Rajinthan
Rameshkumar

Architecture

The amplifier uses a common-source input stage with an active current-mirror load, followed by a common-source second gain stage. A Miller compensation capacitor between the two stages ensures stability. An on-chip bias network derives both the reference and load currents from a single external Iref of 5 µA, making the design self-contained for tapeout. An EN pin pulls the quiescent current down to 2 nA in disable mode.

Target Specifications

• SupplyVDD = 1.8 V
• Bias currentIref = 5 µA
• Input common-mode≈ 0.9 V
• Open-loop DC gain≥ 80 dB
• Unity-gain bandwidth4 MHz
• Phase margin≥ 60°
• Disable current2 nA
• LoadHigh-impedance (7 pF)

Schematic

Simulation Results

IC Layout

Overview

OBO Mouse v4 is an open-source four-wheel differential drive micromouse designed for maze-solving competitions. The robot integrates closed-loop PID velocity control with quadrature encoder feedback, a gyroscope/IMU for heading correction, and IR sensors for wall detection. The chassis is lightweight and 3D-printable; the PCB consolidates all electronics into a compact 2-layer board designed in EasyEDA.

Component Spec

• MCUSTM32F405 (ARM Cortex-M4)
• MotorsCoreless 1215 + magnetic encoders
• Motor driverDRV8833 (×2)
• IMUICM-42688
• IR sensorsTEFT4300 + SFH4545
• Power2S Li-Po 250 mAh
• FirmwareSTM32CubeIDE · HAL · C++
• DebugHC-05 Bluetooth UART · 115200 baud

Mechanical Design & Iterations

PCB Design

Drive System Assembly

Competition & Award

Run Videos

Overview

A reconfigurable robotic end effector designed for automated depalletizing in supermarket warehouse logistics. The system combines vacuum suction cups for box lifting, pneumatic cylinders for lateral stabilization, and ToF sensors for real-time angular alignment — enabling the gripper to adapt to boxes of varying sizes and weights without manual reconfiguration. The Altium-designed PCB integrates RS485, UART, and SPI interfaces with solenoid switching and flyback protection on a 2-layer board.

Component Spec

• MCUATmega2560 (multi-UART)
• Stepper motor42HSE47 closed-loop
• PneumaticsAirtac TN10×50 / MAL16×100
• Suction cupsSchmalz FSG 20 NBE-ESD
• Vacuum ejectorAirbest AZH10BS
• ToF sensorsNOOPLoop TOFSense-M
• PCB2-layer · Altium Designer · JLCPCB
• EnclosureZinc-coated sheet metal

Design Process

Mechanical & PCB

Why I Built This

As an undergraduate in Electronic and Telecommunication Engineering, I frequently needed quick-turn prototypes to test designs before finalizing them. Breadboards and dot boards don't cut it for SMD packages, complex routing, or sensitive analog circuits where parasitics from long wires introduce unwanted behaviour. Ordering from JLCPCB or PCBWay is ideal for final boards, but the 1–2 week turnaround and international shipping cost slowed rapid iteration — something I couldn't afford during competitions and tight project schedules.

Method 1 — CNC Milling

Bought and modified a small CNC machine to accurately mill copper-clad boards. A single machine handles PCB milling, drilling vias and through-holes, and custom board outlines. Achieved trace widths down to 0.4 mm. No chemicals involved, fast turnaround, and ideal for single-layer prototypes. The main limitation is difficulty aligning two-layer boards and the need for regular bit calibration.

Method 2 — UV Mask + FeCl Etching

Used a UV-curable photoresist mask and ferric chloride to etch copper traces, achieving finer detail down to 0.2 mm trace widths — better suited to densely packed circuits. The trade-off is a more time-consuming process, chemical handling and disposal, and separate steps needed for drilling and board cutting.

CNC in Action