16. System Integration

Robot Arm Lamp System Integration Plan

Project Title: Robot Arm Lamp inspired by Pixar Luxo Jr.

Final Project Timeline

This timeline shows the planned milestones for completing the final project, from system integration planning to fabrication, assembly, testing, and final documentation.

Final project timeline showing the planned milestones and deadlines.

System Architecture

The planned system is organized around one ESP32-S3 board, a 7.4 V power rail, and a daisy-chained servo bus. The diagram below shows the relationship between power, control, sensing, output, and user interface layers.

Planned system block diagram for power, control, sensing, actuation, and interface.

Subsystem Map

Mechanical Integration

The lamp is designed to have three degrees of freedom. Each joint will be driven by one STS3215 servo: base yaw, arm pitch, and head tilt. The base is planned to contain the PCB and ballast weight, while the arm sections will be hollow so cables can pass through the structure.

Side-view planning sketch showing the three main motion axes and base structure.

3D Printed Parts

Joint Bracket Design

Each joint uses the same U-bracket principle. The servo is fixed between two side walls, with one side supporting the bearing/bushing and the other side connected to the servo output shaft.

• Inner width: 22 mm, giving the 20 mm servo body 1 mm clearance on each side.
• Wall thickness: 4 mm.
• M3 screws pass through the side walls into the servo mounting holes.

Cable Routing

Cable routing is one of the most important integration risks in this design. The STS3215 daisy-chain bus reduces the number of wires because all servos share VCC, DATA, and GND. This means only the bus wires need to travel through the full arm, and each servo can tap into the bus locally.

Electronics Integration

The main PCB is designed to fit inside the base. It will contain the ESP32-S3, 3.3 V regulation, USB-C programming connection, servo bus connector, I2C connector, MOSFET LED driver, reset and boot buttons, and filter capacitors.

STS3215 Half-Duplex UART

This is the most critical electronic integration detail to verify. STS3215 servos use half-duplex communication, so transmit and receive share one data wire.

ESP32-S3                          STS3215 Daisy Chain

GPIO17 TX -- 100 ohm --+
                       +---- DATA ---- Servo #1 ---- Servo #2 ---- Servo #3
GPIO18 RX -------------+

7.4 V power rail ---------------- Servo VCC
GND ----------------------------- Servo GND

The 100 ohm resistor on TX helps prevent bus contention when the servo sends feedback data back to the ESP32-S3.

Power Budget

The planned supply is a 7.4 V 3 A DC adapter. I also plan to add a 470 uF capacitor near the servo power rail to absorb current spikes during movement.

Software Integration

The planned firmware combines low-level device drivers, behavior logic, and a web interface. I will use a layered structure so each subsystem can be tested independently before final assembly.

Layer 4: User Interface
  Web page with joint sliders, preset pose buttons, animation triggers, status display

Layer 3: Behavior and Animation
  State machine: IDLE, CURIOUS, WORKING, SLEEPING
  Animations: wake, nod, dance, greet, idle micro-motions

Layer 2: Device Drivers
  SCServo library, LED PWM driver, VL53L1X driver, touch read

Layer 1: Hardware Abstraction
  UART1 at 1 Mbps, LEDC PWM at 5 kHz, I2C at 400 kHz

Key Firmware Structure

#include <SCServo.h>
#include <WiFi.h>
#include <WebServer.h>
#include <Wire.h>

#define STS_RX    18
#define STS_TX    17
#define LED_PIN   4
#define TOUCH_PIN 6
#define I2C_SDA   8
#define I2C_SCL   9

#define ID_BASE 1
#define ID_ARM  2
#define ID_HEAD 3

struct Pose {
  int base;
  int arm;
  int head;
  int led;
};

Pose POSE_HOME  = {2048, 2048, 2048, 100};
Pose POSE_SLEEP = {2048, 2700, 2900, 0};
Pose POSE_WORK  = {2048, 2400, 2700, 255};

Integrated Behaviors

Web Interface Routes

Packaging

The packaging goal is to make the lamp look like a finished consumer product instead of a loose prototype. The planned design will hide wires, PCB, and solder joints while keeping the lamp serviceable.

Base Interior Layout

Top view, base cover removed

+--------------------------------------+
|                                      |
|   PCB, 60 mm x 45 mm                 |
|   ESP32-S3, LDO, MOSFET, capacitors  |
|             |                        |
|             | cables up              |
|      Base yaw servo bracket          |
|                                      |
|   Steel ballast plate, about 300 g   |
|                                      |
|   DC jack and USB-C at rear          |
+--------------------------------------+

Lamp Head Detail

The lamp head is planned to contain the lighting module, a small aluminum plate for heat spreading if needed, and a frosted acrylic diffuser press-fit into the shade rim. This should keep the light softer and reduce the risk of overheating.

Planned Assembly Process

I will assemble the system in stages, testing each layer before hiding it inside the final enclosure. This should make it easier to identify whether a problem comes from electronics, wiring, mechanical constraints, or software calibration.

Planned Bill of Materials

This is my estimated material list for the integrated prototype. The final quantities and cost may change after fabrication and assembly.

Expected Challenges and Planned Solutions

Integration Notes Before Building

• Each subsystem should be tested before final assembly, especially each servo's ID and motion range.
• STS3215 servo IDs must be configured one at a time because all new servos start with the same default ID.
• Cable routing is part of mechanical design, not only electronics. I need to keep enough room inside the arms for flexible wires and slack loops.
• Weight distribution is critical for an articulated lamp. I need to test the base stability with the arm fully extended.
• Software calibration must happen after mechanical assembly because servo horn position changes the real HOME pose.
• The 100 ohm resistor on the TX line is important for reliable half-duplex servo communication.

Files

Source document: Week 16 System Integration - Robot Arm Lamp

Planning Checklist

This checklist tracks whether the integration plan covers the Fab Academy system integration requirements. The status will be updated after the physical build and test documentation are completed.

Hero Shots and Video Plan

Photos and videos I plan to add after the final physical build is ready:

• Complete product at a 45 degree angle, lamp on, dark background.
• Side view showing the joint structure.
• Working scene where the lamp illuminates a book or keyboard.
• Open base photo showing the internal PCB and cable routing.
• Exploded layout photo with all printed and electronic parts arranged clearly.
• Short function video: power on, wake animation, touch interaction, and web control.