Weekly Assignments Final Project About me

Project Development

Timeline

What tasks have been completed, and what tasks remain?

By the time of final project presentations;

What's working? what's not?

What questions need to be resolved?

These questions are yet to be resolved:

What will happen when?

This question has been answered clearly in the section on Time Management

What have you learned?

Apart from the skills I have learnt as a part of other weeks, I have used the following processes in this project:

Time Management

I made multiple attempts at scheduling my work, and I failed most of the time. The biggest reason being I underestimated the time I would required to complete a specific task

You can see my schedule here

Week 18: Assessing Project Progress

This is an assessment of my progress as of 29-05-2025:

  • What tasks have been completed, and what tasks remain?

    • Master PCB design ✖
    • Mount PCB design ✖
    • Master PCB production ✖
    • Mount PCB production ✖
    • Master PCB production ✖
    • CAD Add screw mounts in TV head ✖
    • CAD Modify the external design of the TV Head ✖
    • Confirm position of servos and add space for wire management for TV head ✖
    • Design legs based on Otto reference ✔
    • Test TOF TOF LiDAR sensor enclosure ✖
    • Program TOF TOF LiDAR sensor ✖
    • 3D print enclosure - 50%; Printed legs
    • Assemble everything - 30%; Assembled legs
    • Move one leg ✖
    • Program a forward walk cycle ✖

    Because I was struggling to design an integrated PCB and electronics enclosure that is easily dissassemblable for repairing, my instructor advised me to rethink my approach and start with the servo controlled legs. Also I greatly overestimated my speed and efficiency.

  • What's working? what's not?

    At this point in time:

    • The servos are not rotating 180 degrees completely
    • The speakers can be operated using the MAX98357A amplifiers
    • Kerf bending cannot be used to make the lasercut enclosure from birchwood without some kind of supporting material to strengthen the wood layer.
    • I was not successful in making silicone molds from vacuum forming.

  • What questions need to be resolved?

    • Can my robot walk successfully now that I know that the servos cannot rotate complete 180 degrees?
    • Can I finish a minimum viable project in time; A TOF TOF LiDAR input, Display anf servo output, and a LiPo battery for charging.
    • To simplify my design, I plan to change my microcontroller to a Xiao ESP32 to be able to easily program it without a programmer and to charge it with a LiPo battery.

  • What will happen when?

    I am cutting out a lot of features. Right now all I have is a TFT display that can display some emotions, servo legs that help it walk, and a TOF TOF LiDAR input. The microcontroller will likely be a Xiao ESP32. I will be making a new schedule with the deadline of finishing within 6th June 2025

  • What have you learned?

    Time management is crucial to successfully complete a project. This is one aspect I need more practice in.

Making Mockups in Cardboard

08-05-2025: I lasercut a mockup design of my final project.

To test screw hole placement, I made laser cut mockups of my PCB design

I tested how the PCBs could fit without fasteners using a mechanism similar to a drawer slide.

User Flow and Functional Flow

09/05/2025- During System Integration Week I made a system diagrams for user flow and function flow based on instructions from our instructor. This helped us in finalising all the electronics that would be used.

Later on, as I simplified my design due to time constraints, I updated the User and FunctionalFlow

Sketching an Exploded View

10-05-2025: Updated a sketch showing an exploded view of of my final project and how each compenent will be integrated

13/05/2025-Today I confirmed the pinouts for ESP32-WROOM-32E. This guide to pinouts for ESP32 by Random Nerd Tutorials helped a lot, especially when I found it difficult to understand the terminology used in the official datasheet

SD Card Reader & TFT Display

Pin Description
3.3V Power Supply
GND Ground
SCK SPI Clock
MISO SD Card Reader
MOSI
CS (SD) Chip Select for SD
CS (TFT) Chip Select for TFT (any GPIO)
RST Reset

Note: LED ➝ 3.3V, SPI interface used

LiDAR Connections

Pin Description
3.3V Power Supply
GND Ground
SCL I2C Clock
SDA I2C Data

MAX98557 Audio Amplifier

Pin Description
LRC Left-Right Clock
BCK Bit Clock
DIN Data In
GAIN Connect to GND
GND Ground
5V Power Supply

Output ➝ Speaker

Servo Motor (x4)

Pin Description
Signal Control Signal
GND Ground
+5V Power

ESP32 WROOM-32E Pin Mapping

ESP32 Pin Function
IO0 BOOT
GND Ground
3V3 3.3V Power
26 GND
27 LRC
26 BCLK
25 DIN
32 SDA
33 S2
34 S3
12 S4
23 MOSI
18 SCK
15 CS (TFT)
5 CS (SD)
4 RST
2 DC
19 MISO
21 SCL

Notes: “Don't use GPIOs 36, 39 – Analog only” and power requirements include 5V, 3.3V, and GND.

30-05-2025- An ongoing discussion was whether to opt for ESP32WROOM controlling everything or for a Xiao ESP32 C6 (to control the LIDAR TOF sensor, the TFT Display and the speaker) and Atiny 1614 combination (to control the Servo legs). Today, I decided to go with the Xiao-Attiny combination for more pinouts and an easier time in routing traces

These changes were integrated into the CAD design of the TV head as well

Testing TFT display

09-05-2025: Testing refresh rate of LCD screen to play animations and video footage

Testing Kerf Bending with Birch wood

12/05/2025- I tested kerf bending with 3mm birch wood. My test was a fail, since the radius needs to be at least 15 mm.

This led me to scrap the idea instead replacing it with vinyl cut wrapper to mimic a wood finish

Speaker Testing

13/05/2025- Initially, I had chosen to purchase a 8 Ohm 2W speaker as shown below. I used measurements I obtained from online to make CAD models that I integrated into my early designs. Along with this speaker, I planned to use the MAX98357A Class D amplifier in combination with the ESP32-WROOM-32E

Source: Probots

23/05/2025- But due to constraints in procurement, I had to switch to using the iPhone 6 Plus speaker

I was able to successfully test the functioning of the SD card player with the MAX98357A audio amplifer and the iPhone 6 Plus speaker with the help of Revi's code

Later on the MAX98357A audio amplifer was switched for DFPlayer Mini to reduce the complexity of PCB designing

CAD Design

11-16/05/2025: I started CAD designing, trying to integrate different electronics into a limited spaces

I made a finalised CAD model of my design that integrates all the electronics. To do this I first arranged all the electronics placement, then went to KiCAD if connections can be made in the desired arrangement, make minor changes, then reintegrate those changes in the CAD model.

As for aesthetics, I wanted it be small and cute. Initally I opted for a more rounded design to achieve this effect, but later on I changed it to more hard edges since old TVs had more hard edges rather than rounded corners

23/05/2025: Due to many changes in the design, I decided to start from scratch from the ground up after some advice from our instructor

I started with designing the legs downloaded the STEP files of OTTO and used that as a reference to design my walking mechanism in Fusion, accommodating for changes in:

Then I went on to testing the walking mechanism programmatically before I designed the TV head

Since I faced a lot of difficulties in routing traces for the PCB, I reduced or simplified the electronics inside. After some iterations this is how how the system integration of the Electronics would look like.

Then I made a CAD design showing how the inner electronics will be assembled. The screw holes will be used to mount each component

PCB Design

I designed two PCBs, the bigger 'mount' PCB that holds the front facing electronics; the LCD display and the switches, along with the battery on the back side. On this PCB, I stacked another doublesided PCB that holds all the internal electronics; including the microcontroller, the buck converter, the amplifer, along with the USB port and the micro SD card reader

I used this schematic that connected the microSD card directly to their microcontroller. I adapted this for my Use

Question: Will the SD card work without pullup resistors between MOSI, MISO and SCK connections.

After I arranged all the components in Fusion, I projected a sketch of placements into KiCAD and used that as a reference to make my final PCB design, Due to pads and spaces for traces, the design will be slightly modified from original. Once my mount PCB design was done, I exported a CAD model back into Fusion, projected all reference geometries including from the battery, 2x3 pin headers, JST connectors and screw holes and edge cut of mount PCB into a new sketch that I exported as a DXF that I brought once again into KiCAD to repeat the steps.

To make sure I align the male pins and female sockets of both PCBs, I copy and paste PCB layout from PCB mount and line it up on top of my DXF sketch. I then delete all the components apart from the pin sockets and lock it to prevent it from being removed when I update the design. Then I manualluy adjusted the position of the headers by looking at the 3D view to get the best possible alignment. Since the pads are long enough, minor adjustments can be made as long as the header is nearly on top of the sockets

I then modified the Audio Amplifer Pads to be an SMD type

Since I did not find any datasheet for the BEC buck converter except external dimensions, I made an educated guess that since the module mostly likely uses 2.54 mm pitch header pins, the spacing of the holes will also be the same as other components like header pins.

Fabrication

I was able to start fabrication and I sorted some issues with the servo leg. I was succesful in fully assembling one pair of servo upper leg and feet

Once I corrected the issues with the first servo leg in CAD, I got a correct 3D print of the other leg This is how it looks once assembled

Then I proceeded to program a basic walk cycle before continuing with fabrication of the rest of the parts

I 3D printed the TV Head in black PLA and the feaures in white, then I pressfit both of them together, and added a bit of superglue from behind to fix them together. I then used the vinyl cutter to add a wood-grain finish on the TV Head

For detailing I used a wood grain vinyl sheet to wrap the TV Head enclosure

Credit: Turntable from Ashish's Symphoni Fab Academy Final Project

Programming a Walk Cycle

29/05/2025- I was not able to use the <Otto> library and its example code due to a problem with the <SoftwareSerial.h> library. To speed things up, I used the help of ChatGPT

ChatGPT Prompt 1: Generate Arduino code for 4-servo walking gait based on _execute function logic

Prompt 1: Generate Arduino code for 4-servo walking gait based on _execute function logic

Based on your `_execute()` function in Otto's library, here is an adapted Arduino code that uses oscillation for 4 servos to generate a walking gait:

 #include <ESP32Servo.h> #include <math.h>

        // Create servo objects
        Servo R2, R1, L2, L1; // Right Foot, Right Hip, Left Foot, Left Hip

        // Define servo pins
        int R2pin = D1;
        int R1pin = D2;
        int L1pin = D3;
        int L2pin = D4;

        // Oscillation parameters
        float amplitude[4] = {30, 30, 20, 20}; // Swing amplitude (degrees)
        float offset[4] = {0, 0, 4, -4}; // Neutral position offset
        float phase[4] = {0, 0, -PI/2, -PI/2}; // Phase difference (feet lag behind hips)
        int T = 1000; // One gait cycle in ms

        unsigned long startTime;

        void setup() {
        Serial.begin(9600);

        // Allocate all timers
        ESP32PWM::allocateTimer(0);
        ESP32PWM::allocateTimer(1);
        ESP32PWM::allocateTimer(2);
        ESP32PWM::allocateTimer(3);

        // Set frequency for each servo
        R2.setPeriodHertz(50);
        R1.setPeriodHertz(50);
        L1.setPeriodHertz(50);
        L2.setPeriodHertz(50);

        // Attach servos to pins
        R2.attach(R2pin, 1000, 2000);
        R1.attach(R1pin, 1000, 2000);
        L1.attach(L1pin, 1000, 2000);
        L2.attach(L2pin, 1000, 2000);

        // Center all servos at 90°
        R2.write(90);
        R1.write(90);
        L1.write(90);
        L2.write(90);

        delay(1000); // Give servos time to center
        startTime = millis();
        }

        void loop() {
        walkCycle(1.0); // One step
        delay(50); // Short delay before repeating
        }

        // --- Function to oscillate the servos in a step ---
        void walkCycle(float steps) {
        float t;
        float theta[4];
        unsigned long currentTime;

        while ((millis() - startTime) <= T * steps) {
        currentTime = millis();
        t = (currentTime - startTime) / float(T);

        for (int i = 0; i < 4; i++) {
        theta[i] = amplitude[i] * sin(2 * PI * t + phase[i]) + offset[i];
        }

        // Centered around 90°
        L1.write(90 + theta[0]);
        R1.write(90 + theta[1]);
        L2.write(90 + theta[2]);
        R2.write(90 + theta[3]);

        }

        startTime = millis(); // Reset time for next step
        }
  • The hips (L1, R1) swing with 30° amplitude, feet (L2, R2) with 20° amplitude.
  • Feet lag behind hip swing by 90° phase shift to simulate realistic stepping.
  • Each servo oscillates around its center (90°), creating a walking pattern.
  • This mimics the Otto _execute() and oscillateServos() logic in a simple standalone sketch.
                        #include <ESP32Servo.h>
                        #include <math.h>

                        // Create servo objects
                        Servo R2, R1, L2, L1; // Right Foot, Right Hip, Left Foot, Left Hip

                        // Define servo pins
                        int R2pin = D1;
                        int R1pin = D2;
                        int L1pin = D3;
                        int L2pin = D4;

                        // Oscillation parameters
                        float amplitude[4] = {30, 30, 20, 20};     // Swing amplitude (degrees)
                        float offset[4]    = {0, 0, 4, -4};        // Neutral position offset
                        float phase[4]     = {0, 0, -PI/2, -PI/2}; // Phase difference (feet lag behind hips)
                        int T = 1000;                              // One gait cycle in ms

                        unsigned long startTime;

                        void setup() {
                        Serial.begin(9600);

                        // Allocate all timers
                        ESP32PWM::allocateTimer(0);
                        ESP32PWM::allocateTimer(1);
                        ESP32PWM::allocateTimer(2);
                        ESP32PWM::allocateTimer(3);

                        // Set frequency for each servo
                        R2.setPeriodHertz(50);
                        R1.setPeriodHertz(50);
                        L1.setPeriodHertz(50);
                        L2.setPeriodHertz(50);

                        // Attach servos to pins
                        R2.attach(R2pin, 1000, 2000);
                        R1.attach(R1pin, 1000, 2000);
                        L1.attach(L1pin, 1000, 2000);
                        L2.attach(L2pin, 1000, 2000);

                        // Center all servos at 90°
                        R2.write(90);
                        R1.write(90);
                        L1.write(90);
                        L2.write(90);

                        delay(1000); // Give servos time to center
                        startTime = millis();
                        }

                        void loop() {
                        walkCycle(1.0); // One step
                        delay(50);      // Short delay before repeating
                        }

                        // --- Function to oscillate the servos in a step ---
                        void walkCycle(float steps) {
                        float t;
                        float theta[4];
                        unsigned long currentTime;

                        while ((millis() - startTime) <= T * steps) {
                            currentTime = millis();
                            t = (currentTime - startTime) / float(T);

                            for (int i = 0; i < 4; i++) {
                            theta[i] = amplitude[i] * sin(2 * PI * t + phase[i]) + offset[i];
                            }

                            // Centered around 90°
                            L1.write(90 + theta[0]);
                            R1.write(90 + theta[1]);
                            L2.write(90 + theta[2]);
                            R2.write(90 + theta[3]);
                        }

                        startTime = millis(); // Reset time for next step
                        }

Conclusion

Notes for the Future

  • How to replicate PCB layouts in KiCAD
  • Using design blocks in KiCAD
  • Design multiple PCBs in KiCAD
  • Projecting pads and importing DXF does not help with aligning header pins and socket pins

    • Add Mistakes only in Mistakes and Solutions section to avoid break in flow

    References

    References to help reader understand in detail

    Look at previous year documentation

    Design Files

    Click here to access the project files