Project files

05 — Structural Assembly and Wiring Guide

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📸 Operation diagram:

3D-printed Parts Assembly

Parts List

Assembly Steps

Step 1: Install the Base

1. Place bottom.stl flat on the work surface.
2. Install the 4 servos into the pre-cut slots on the base.
3. Secure with screws (M2 screws recommended).

Step 2: Assemble the Body

1. Align body.stl with the base.
2. Fasten the two parts together from the bottom using screws.
3. Route the wiring through the internal cavity of the body.

Step 3: Install the Feet

1. Attach the 4 foot.stl parts to the servo arms.
2. Adjust each foot to the initial angle (90 degrees).

Circuit Wiring Diagram

                         +5V (direct battery supply)
                          │
    ┌─────────────────────┼──────────────────────────┐
    │                     │                          │
Servo1~4 red wire → 5V    Speaker + PIN       HLK-V20
                   ┌────┤ NPN                      │
                   │ 1KΩ│ Triode                    │
GPIO16(D0) ────────┘    │ E                         │
                         │ GND                       │
ESP12F                                               │
┌────────────────────────────────────────────────────┤
│                                            GPIO0 ──┤← HLK-V20 TX
│ GPIO14 ──1KΩ── Servo1 + OV2640_SCK                │
│ GPIO12 ──1KΩ── Servo3 + OV2640_MISO               │
│ GPIO13 ──1KΩ── Servo4 + OV2640_MOSI               │
│ GPIO15 ──▶ OV2640_CS + 10KΩ↓GND (⚠ must!)         │
│ GPIO16 ──▶ Speaker (triode drive)                 │
│ GPIO0  ──▶ HLK-V20 TX (SoftwareSerial RX)         │
│ GPIO2  ──◀ Button 1 → GND (INPUT_PULLUP)          │
│ GPIO4  ──▶ OLED SDA (I2C)                         │
│ GPIO5  ──▶ OLED SCL (I2C)                         │
│ A0     ──▶ Voltage divider → Battery+             │
│ TX(GPIO1) → USB-TTL RX (debug port)               │
│ RX(GPIO3) → USB-TTL TX (debug port)               │
└────────────────────────────────────────────────────┘

Detailed Wiring of Each Module

Servos ×4

⚠️ Connect all servo red wires to 5V battery direct supply (do not connect to ESP's 3.3V!)

OLED Display (SSD1306, I2C)

OV2640 Camera (ArduCAM Mini, SPI)

HLK-V20 Voice Module (UART)

Speaker (Transistor Driven)

                    +5V
                     │
                    ╱
                  ╱ Speaker (8Ω/0.5W)
                  ╲
                    │
                    │  C
GPIO16 ──[1KΩ]───── B  NPN (S8050/2N2222)
                      E
                      │
                     GND

Power Supply Solutions

MindPaw supports two power supply methods:

Option A: USB Power (Recommended, ¥0)

This is the most cost-effective method, using a phone charger + MicroUSB cable:

Phone charger (5V/1A+) ── MicroUSB cable ── ESP12F development board USB port
                                    │
                                AMS1117 regulated to 3.3V
                                    │
                            ┌───────┴───────┐
                            │               │
                         Servo 5V          OLED/OV2640/HLK-V20 3.3V

⚠ SG90 servo stall current ~700mA, peak current for 4 servos ~2.8A. It is recommended to use a charger with 5V/2A or higher. If the servos stall, try a charger with higher current. During normal walking, average current is ~500mA, so a standard phone charger is sufficient.

Option B: Battery Power (Optional, ¥30+)

When mobile use (without a wired connection) is required, add a 2S lithium battery:

Battery Voltage Divider Circuit (ADC Detection):

Battery+ (8.4V max) ── R1 (100KΩ) ──┬── A0 (ESP12F)
                                    │
                                R2 (12KΩ)
                                    │
                                   GND

💡 Money-saving tip: Use the tea-brewing base or USB power for development and debugging first. Once everything is working, decide whether to add the battery.

⚠️ Key Notes

Prerequisites for Booting

Debugging Tips

1. First Power-On: Connect only the ESP12F + USB-TTL first, and confirm that the serial port outputs logs.
2. Servo Not Moving: Check if the 5V power supply is normal and if the servo signal wires are connected correctly.
3. OLED Not Lighting Up: Check the I2C pull-up resistors (4.7KΩ) and confirm the address is 0x3C.
4. HLK-V20 Not Responding: Use a USB-TTL to connect to the module and confirm that the configuration has been flashed.
5. OV2640 Not Working: Check the GPIO15 pull-down resistor and the 1KΩ resistor shared with SPI.