Overview
The LED matrix driver board uses the ATmega328P microcontroller. It controls an 8×8 or 16×16 common-cathode LED matrix using multiplexing technology. Core components:
- Row driver: ULN2803 Darlington array (sink current 500mA/row)
- Column driver: 74HC595 shift register (cascade expansion)
- User input: 3 touch buttons
- Power supply: 5V regulated (supports USB/external DC input)
- Current limiting resistor: 220Ω (independent for each column)
Sample Application
- Scrolling text: Display real-time sensor data
- Interactive game: Snake (button controls direction)
- Animation effect: Beating heart/wave pattern
- Music visualization: With microphone module
Current version limitations
| Limitation | Impact | Workaround |
|---|---|---|
| 16×16 Refresh Rate ≤200Hz | Flicker at high brightness | Use timer interrupts |
| No PWM Dimming | Fixed brightness | Add MOSFETs in next rev |
| USB Power Limit (500mA) | Max 25% LEDs lit | External 5V/2A supply |
Installation Guide
Firmware Burning
- Connect FTDI programmer to 6-pin interface
- Install LedControl library in Arduino IDE
- Upload sample code:
cpp
//
#include <LedControl.h>
LedControl lc = LedControl(12, 11, 10, 2); //
void setup() {
lc.shutdown(0, false);
lc.setIntensity(0, 8);
}
Firmware architecture
Code
graph TD
A[Main loop] --> B[Scan button]
A --> C[Generate animation frame]
A --> D[Refresh matrix]
D --> E[Activate row N]
D --> F[Send column data]
F --> G[Latch 74HC595]
Key optimizations:
- Timer interrupt refresh (avoids delay() blocking)
- Frame buffer pre-rendering
- Button state machine debounce
Hardware design
PCB layout points
- Current path design:
- Power inlet → 100μF electrolytic capacitor → LM7805 → 0.1μF ceramic capacitor
- Row driver (ULN2803) directly connected to matrix row
- Signal grouping:
- Row control signal: 20mil line width, length matching ±5mm
- Column data link: DIN-CLK-LATCH group routing
- [Current limiting resistor] layout:
- Close to 74HC595 output pin
- 0805 package parallel design (enhanced heat dissipation)
Via Specifications
| type | Aperture | Pad diameter | use |
|---|---|---|---|
| power supply | 0.4mm | 0.8mm | 5V/GND |
| Signal | 0.3mm | 0.6mm | Row and column control |
| Heat dissipation | 0.5mm | 1.0mm | Regulator Ground |
FAQ
[Firmware burning] failed
Check the FTDI driver installation
Verify whether the Bootloader is damaged
Measure MCU clock frequency (should be 16MHz)
Uneven LED brightness
Increase row drive capability: add 100μF capacitor to the output of ULN2803
Shorten the length of the trace (key: [PCB trace] ≤10cm)
[Current limiting resistor] overheating at high brightness
Recommendation: Use 1210 package resistors (power ≥ 0.5W)
Or use constant current driver IC (such as TLC5940)
16×16 matrix edges are dark
Add 100nF decoupling capacitor at the end of the line
Use “snake” routing to balance impedance
Design Files
The download KiCad project contains:
- Schematic (with [current limiting resistor] calculation annotation)
- PCB layout (4-layer board optimized version)
- 3D model (STEP file)
- Bill of Materials (BOM)
Upgrade route
- V2.0: Added WiFi control (ESP-12F module)
- V3.0: Support RGB matrix (IS31FL3731 driver IC)
- V4.0: Integrated lithium battery management (charge and discharge circuit)
