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Line-Tracking Robot

Video Demo

Process Image Catalog

1. Design Line Sensor Circuit and MCU Circuit with Altium

Components in the Line Sensor Circuit:

  1. Resistors 220 Ohm (8)
  2. Photoresistors (8)
  3. White LEDs (16)
    • Function: Illuminate the surface to enhance the photoresistors' ability to differentiate the line color from the road.
  4. 10-pin Header (1)
  5. 10k Resistor Network (1)

Line Sensor Circuit

Components in the MCU Circuit:

  1. ESP32 DEV KIT V1 (1)
  2. 2-pin Headers (3)
  3. Capacitors:
    • 100nF (1)
    • 300nF (1)
  4. LM7805 (1)
    • Function: Voltage regulator to ensure a stable 5V power supply for the entire circuit.
  5. MOSFETs (2)
    • Function: Control the two wheels of the robot.
  6. Resistors:
    • 1k
    • 10k
    • 150k
  7. Diodes
    • Function: Prevent back EMF from damaging the MOSFET when the motor suddenly stops.
  8. 10-pin Header (1)

MCU Circuit

2. Wiring Diagrams of Both Circuits

Wiring Diagram 1
Wiring Diagram 2

3. Etching Copper PCB Using Specialized Etching Salt

  • Tips:
    • If the copper traces fade after printing on the PCB, you can redraw them with a marker.
    • Using hot water accelerates the etching process and results in cleaner traces.

Etching Process 1
Etching Process 2

4. Soldering Components onto the Circuit

Soldering Process 1
Soldering Process 2
Soldering Process 3
Soldering Process 4

Coding Workflow

1. Calibrate ADC

  • Read the values from the 8 photoresistors, ensuring they are consistent in the same environment.
  • -> Determine the threshold for distinguishing between the line and the road.

2. Reduce Duty Cycle -> Slow Down the Motor and Calculate the Error

  • Error = Target - Pos
  • If Error > 0, the right wheel should spin faster to turn right.
  • If Error < 0, the left wheel should spin faster to turn left.

3. Handle Line Loss

  • Rotate one wheel to locate the line.

4. Tune Ki, Kp, Kd Parameters -> Determine the Optimal Values

  • PID -> PWM -> Loop
  • Initially, set a high 𝐾p for quick error response.
  • Gradually increase 𝐾i to reduce accumulated error (if the robot becomes unstable).
  • Use 𝐾d to minimize overshoot and oscillations.