Project Overview
This project showcases foundational mechatronics engineering laboratory and simulation coursework developed during Stages 2 and 3 at the University of Basrah. It encompasses transient SPICE circuit analysis of MOSFET switching topologies with RC snubbers, low-level 8086 assembly language programming for microprocessor control, Proteus logic simulation, and COMSOL multiphysics finite element modeling.
Problem and Motivation
Mechatronics systems bridge the gap between software algorithms and physical actuators (motors, solenoids, valves). Software commands must ultimately drive power electronics. High-speed switching circuits generate dangerous inductive voltage spikes and thermal transients that destroy microcontroller pins if not properly damped. Mastering circuit dynamics and register-level assembly is non-negotiable for true mechatronics engineering competence.
Requirements and Constraints
- ■Sub-microsecond transient response damping to protect driver gates from inductive kickback.
- ■Deterministic instruction execution cycle timing on 8086 assembly routines.
- ■Accurate netlist representation matching physical lab bench testing components.
My Role & Contributions
- ›Calculated RC snubber component values and gate drive resistor limits.
- ›Simulated transient switching waveforms and flyback diode protection in LTspice.
- ›Wrote 8086 assembly routines for memory-mapped I/O and interrupt handling.
System Architecture
Hierarchical engineering analysis flow from mathematical design to SPICE simulation and microprocessor firmware.
1. Circuit Topology & Netlists
Power MOSFET switching bridge, freewheeling diode protection, and inductive load modeling.
2. Transient Numerical Simulation
LTspice SPICE engine solving non-linear differential equations across microsecond intervals.
3. Microprocessor Firmware
8086 Assembly source instructions executing on emu8086 simulator for precise hardware timing.
Technical Implementation
MOSFET Gate Drive & RC Snubber Simulation
Simulated the gate-source turn-off transient on an N-channel power MOSFET driving an inductive coil, proving that an RC snubber network suppresses ringing below the MOSFET's breakdown rating.
Important Algorithms & Decisions
Snubber Damping Resistor Calculation
Rationale: Selected damping resistance based on critical damping criterion R = 2 * sqrt(L / C_parasitic) to eliminate high-frequency parasitic oscillation without excessive steady-state power dissipation.
Trade-off: Dissipates minor energy in the resistor to safeguard semiconductor longevity.
Engineering Challenges
Issue: Inductive Voltage Spikes Exceeding Drain-Source Breakdown
Root Cause: Rapid di/dt during MOSFET turn-off induced severe inductive flyback voltage across the coil.
Resolution: Placed a fast-recovery Schottky freewheeling diode in anti-parallel with the load alongside an RC snubber.
Testing & Evaluation
SPICE simulation runs evaluating peak Vds, gate rise times, and current transient curves.
Results & Known Limitations
- ✓Demonstrated stable switching transient suppression across varying load currents.
- ✓Verified register-level assembly routines for input/output timing control.
- ⚠SPICE models assume idealized thermal dissipation; physical bench prototyping requires heatsink thermal resistance budgeting.
Future Improvements
- →Integrate closed-loop PWM PID control firmware implemented in C on an STM32 ARM Cortex-M microcontroller.
Repository & Verification
Public repository on GitHub containing SPICE simulation models and assembly firmware.