This Circuit Theory & Design II project (EELE-3316-WA) demonstrates the design and implementation of a DC motor speed control system capable of maintaining a 48V DC motor at 40 rpm under varying load conditions. The system incorporates a 24V power supply with feedback and speed sensing controls.

The project successfully achieved its main objective through the integration of an H-bridge circuit, ESP8266 microcontroller, and ST188 infrared sensor, delivering reliable speed control with experimental validation showing effective performance under both no-load and full-load conditions.

• PI Control Algorithm: Proportional-Integral controller with Kp=0.09 and Ki=0.001 for optimal response
• ESP8266 Microcontroller: Arduino IDE programmed controller handling speed measurement, PWM generation, and control algorithms
• PWM Control: 500Hz frequency PWM signals with adjustable duty cycle for precise motor speed regulation
• Closed-Loop Feedback: Real-time speed monitoring and automatic adjustment to maintain 40 rpm target
• ST188 Optical Sensor: Infrared sensor providing analog speed feedback with 90 tick marks on motor disk

• Power Transistors: TIP31C npn and TIP32C pnp transistor pairs for 24V DC motor drive
• Opto-Isolation: 4N33 optocouplers protecting ESP8266 from high voltage H-bridge circuit
• Protection Diodes: 1N4148 diodes preventing reverse voltage damage during switching
• Heat Management: Aluminum profile heat sinks for effective transistor thermal dissipation
• Current Limiting: Series resistors (1.8kΩ, 1.2kΩ, 140Ω) for proper base current control

• Motor Specifications: 50V class B DC motor with armature resistance of 17.85Ω and field resistance of 279.45Ω
• Separately Excited Model: 24V field excitation with armature powered via H-bridge for directional control
• Speed Feedback: Back EMF constant of -0.157 V/rad/s enabling accurate speed calculation
• Load Testing: Validated performance from 0° (no load) to 10° (full load) brake conditions
• Statistical Analysis: No-load: 37.5 rpm ±13.4, Full-load: 47.5 rpm ±4.9 demonstrating effective control

• Duty Cycle Optimization: 76.6% PWM duty cycle required for 40 rpm operation under no-load conditions
• Load Adaptation: Duty cycle adjusts from 76.6% (no load) to 69.5% (full load) for consistent 40 rpm
• Control Gains: Optimal proportional gain (Kp) = 0.09 and integral gain (Ki) = 0.001
• Speed Stability: Average speeds within 20% of target with improved stability under loaded conditions
• Response Time: Fast and stable system response to load variations and setpoint changes

• Circuit Modeling: Complete H-bridge simulation with 80ms transient analysis validation
• PWM Analysis: 500Hz frequency with 76.6% duty cycle producing ±24V motor drive signals
• Thermal Analysis: Heat sink calculations ensuring safe transistor operation below 60°C
• Component Selection: Verified transistor beta values and current ratings through simulation
• Design Optimization: MOSFET alternatives identified for improved efficiency and reduced heat generation

• Hardware: ESP8266 microcontroller, TIP31C/TIP32C transistors, 4N33 optocouplers, ST188 infrared sensor
• Programming: Arduino IDE for embedded C++ control algorithms and PWM generation
• Simulation: LTspice for circuit design validation and transient analysis
• Power Electronics: H-bridge motor drive with 24V supply and protection circuitry
• Control Theory: PI control implementation with error calculation and duty cycle adjustment
• Testing Equipment: Digital multimeter, oscilloscope for PWM analysis and system validation