Chapter 15 — V1 Hardware Deployment

Step-by-Step Build & Test Guide (20cm Cube, 10cm Wheel Base)

This chapter walks you through building and validating the V1 robot in logical, testable stages:

  1. Power Infrastructure
  2. Camera Subsystem (Eyes)
  3. Motor Subsystem (Muscles)
  4. Mechanical Assembly
  5. Calibration (10cm Wheel Base)
  6. Full System Integration

The robot consists of:

  • 20×20×20 cm lightweight cube chassis
  • 10 cm wheel base (center-to-center)
  • 6 cm diameter wheels
  • Two 28BYJ-48 stepper motors
  • ESP32-CAM (vision)
  • ESP32-S3 (motor controller)

Because the wheel base is only 10 cm, the system is mechanically efficient and ideal for the 28BYJ-48 motors.

Stage 1 — Power Infrastructure

Components

  • 5V 3A power supply (recommended)
  • Protoboard (or MB102)
  • 1000uF 16V electrolytic capacitor

Wiring 

5V Power Supply → + Rail
GND Power Supply → – Rail

Capacitor (+) → + Rail
Capacitor (–) → – Rail

Why 3A?

Even though the robot is light, the system includes:

  • 2 steppers
  • 2 ESP32 boards
  • WiFi bursts from ESP32-CAM

3A provides headroom and prevents brownouts.

Stage 2 — Camera Subsystem (Test Independently)

Wiring 

ESP32-CAM 5V → + Rail
ESP32-CAM GND → – Rail

Do NOT use 3.3V.

Validation

Flash camera firmware.

Open:

http://<ESP32-CAM-IP>/stream

Confirm:

  • 320x240 MJPEG
  • ~10fps
  • Stable stream
  • No random resets

If stable → Eyes validated.

Stage 3 — Motor Subsystem (Test Without Chassis)

Left Motor Wiring

ESP32-S3 ULN2003
GPIO 4 IN1
GPIO 5 IN2
GPIO 6 IN3
GPIO 7 IN4

ULN2003:

  • VCC → 5V
  • GND → GND

Right Motor Wiring

ESP32-S3 ULN2003
GPIO 15 IN1
GPIO 16 IN2
GPIO 17 IN3
GPIO 18 IN4

Independent Tests

Left only:

{"cmd":"move_steps","left":1000,"right":0,"speed":600}

Right only:

{"cmd":"move_steps","left":0,"right":1000,"speed":600}

Forward:

{"cmd":"move_cm","left_cm":10,"right_cm":10,"speed":600}

If stable → Muscles validated.

Stage 4 — Mechanical Assembly

Now mount everything onto the 20cm cube.

Important Geometry

  • Outer cube: 20 cm
  • Wheel base (center-to-center): 10 cm
  • Wheel diameter: 6 cm

The smaller 10 cm wheel base:

  • Improves turning efficiency
  • Reduces required torque
  • Increases rotational responsiveness
  • Slightly increases angular sensitivity to calibration errors

Install Ball Caster

Because wheel base is compact (10 cm), ball caster alignment is critical.

If caster has friction:

  • Robot will yaw during straight movement
  • Odometry error increases

Ensure free rolling in all directions.

Stage 5 — Calibration (10cm Wheel Base)

These are your starting physical constants:

Parameter Value
Wheel diameter 6.0 cm
Wheel base 10.0 cm

Apply:

{"cmd":"set_config","wheel_diameter_cm":6.0,"wheel_base_cm":10.0}

Forward Calibration

Send:

{"cmd":"move_cm","left_cm":50,"right_cm":50,"speed":600}

Measure real distance.

If actual = 49cm:

6.0 × (49/50) = 5.88

Apply correction.

Rotation Calibration

Send:

{"cmd":"rotate_deg","degrees":360,"speed":600}

Because wheel base is 10 cm (shorter than previous 12 cm), rotation should feel:

  • Faster
  • More responsive
  • Less torque-demanding

If rotation overshoots:

  • Wheel base constant too small

If under-rotates:

  • Wheel base constant too large

Updated Kinematic Implications (10cm Base)

Angular displacement formula:

angularRad = (rightDistCm - leftDistCm) / wheelBaseCm

With 10 cm base:

  • Same wheel difference produces larger rotation
  • Calibration precision becomes more important

However:

  • Lower inertia
  • Less torque stress on motors
  • More stable at 800 steps/sec

Recommended Speed Limits

Because chassis is light and wheel base compact:

  • Default: 700–800 steps/sec
  • Safe max: 1024 steps/sec
  • Typical linear speed ≈ 4.7 cm/s

This configuration is well within 28BYJ safe torque limits.

Stage 6 — Integrated Test

Reconnect camera.

Confirm:

  • No brownouts
  • Motors move
  • Video stable during motion

Full Rotation + Vision Test

  1. Open camera stream.
  2. Send:
{"cmd":"rotate_deg","degrees":360,"speed":700}

You should see the room rotate smoothly.

Because base is only 10 cm, rotation should appear tight and clean.

Expected Performance (10cm Wheel Base)

With proper calibration:

  • ±1 cm linear accuracy over 50 cm
  • ±2° rotational accuracy
  • No skipped steps at 800 steps/sec
  • Smooth pivot turns

Final Mechanical Summary

Even though the outer cube is 20 cm, the effective drive geometry is compact:

  • Wheel base: 10 cm
  • Wheel diameter: 6 cm
  • Mass: <200g

This makes the robot mechanically efficient and ideal for stepper-based differential drive.

The body is large. The drivetrain is compact. The control loop remains identical.