Multi-layer PCB Design for Consumer Electronics

PCB DESIGN REQUIREMENTS
(FINAL – MECHANICAL CONSTRAINT UPDATED)
1. BOARD OVERVIEW (UPDATED)
PCB Type: Main controller PCB (production-grade)
Board Width: 100 mm (FIXED – DO NOT CHANGE)
Board Length: Variable – minimize as per component layout
Thickness: 1.6 mm
Layers: 4-layer PCB (mandatory)
L1: Signals
L2: Solid GND plane
L3: 5V power plane
L4: Signals
Solder Mask: Matte black
Silkscreen: White
Board Edge: Black
Mounting Holes:
4 × M3 (corner-aligned to final outline)
⚠️ Mechanical Priority:
PCB length reduction is a design objective, provided electrical safety, thermal margin, and connector accessibility are not compromised.
2. POWER SYSTEM
Power Input
Voltage: 5V DC
Current: Up to 10A
Connector: 2-pin screw terminal (5.08 mm)
Protection (mandatory):
Reverse polarity protection
Polyfuse / blade fuse
TVS diode
Power Rails
5V: Servos, PCA9685, TMC2209 motor power
3.3V: ESP32, DS3231 RTC
3.3V Regulator: ≥600 mA (buck or LDO)
3. MICROCONTROLLER
Module: ESP32-WROOM-32
Wi-Fi: Primary control
Reset / Boot: EN + IO0 routed to UART socket
4. SERVO CONTROL SYSTEM (LOCKED)
Drivers
IC: PCA9685
Qty: 4
Interface: I²C
Outputs
Total Servos: 40
Zones (silkscreen mandatory):
Zone 1–4 (10 servos each)
Servo Connector (FINAL & SAVED)
Type: JST-XH
Pins: 3
Lock: Friction-lock
Pitch: 2.54 mm
Mount: Vertical, through-hole
Pinout:
GND
+5V
PWM
Power Layout Rules
≥80 mil equivalent 5V copper
≥470 µF bulk capacitor per zone
Star-routed servo power
5. STEPPER MOTOR SYSTEM
Driver: TMC2209 (×2)
Mode: STEP / DIR
UART: Required
Motor: NEMA 8 (5V)
Motor Connector: JST-XH 4-pin
Thermal: Copper pour + vias under driver
6. REAL-TIME CLOCK
IC: DS3231
Voltage: 3.3V
Backup: CR2032 holder
Bus: Dedicated I²C (GPIO 32, 33)
7. USER INTERFACE (LOCKED)
Push Button: 1 only
Function: Reset / manual mode
Status LED: 1 × Addressable RGB (WS2812)
8. PROGRAMMING & DEBUG (LOCKED)
Connector: UART socket / header
Pins: TX, RX, GND, 3.3V (optional)
USB Connector: ❌ Not used
Auto-boot: EN + IO0 routed
9. LAYOUT & EMI RULES
Solid uninterrupted GND plane
Servo power routed away from ESP32 antenna
Separate routing for:
Servo PWM
Stepper STEP/DIR
Onboard I²C pull-ups (~4.7 kΩ)
Bulk caps close to load zones
10. SILKSCREEN & MARKINGS
RC1 Controller Board
PCB revision
ZONE 1–4 labels
Power polarity
UART pin labels
11. MANUFACTURING DELIVERABLES
Designer must supply:
Schematic (PDF)
PCB layout source files
Gerbers
Pick & Place
BOM with MPNs
3D renders