Creating an LED screen requires a combination of hardware construction and software debugging. The following is a detailed step-by-step description:
1. Hardware Construction Process
Design Planning
Determine parameters: Set screen size (e.g., 128x16 dots), resolution, brightness (indoor brightness is typically 4000-6000 cd/m2), color (single red/dual color/full color), and pixel pitch (e.g., P2.5 represents 2.5mm pitch) based on your requirements.
Selection List:
Core Components: LED unit boards (including driver chips such as 74HC595), power supply (5V/40A, each power supply supports 8-10 units), control card (asynchronous card with power-off memory support), cable (16-pin 08-pin connector), frame, and angle iron.
Supplementary Materials: Magnets (to secure the unit boards), copper standoffs, screws, 5V/220V power cord, and serial cable (RS232 or USB-to-serial).
Tools: Hand drill, multimeter, wire cutters, and soldering iron.
Assembly Structure
Frame Cutting: Measure the screen dimensions, cut the aluminum alloy frame, and install the corners.
Securing the Unit Boards:
Drill holes in the angle iron. Secure the unit boards with copper standoffs and nuts, ensuring consistent orientation.
For example: A 128x16 dot screen requires two 64x16 unit boards connected in series, each secured with four copper standoffs.
Power Supply Installation: Secure the power supply to the frame or angle iron. Connect the VCC (positive) and GND (negative) terminals of three to four unit boards to each power supply. Connect the input terminal to 220V AC and ground it for static electricity protection.
Connecting Wiring
Cable Connection: Use a 16-pin cable to connect the control card to the unit board. Note the connector order (e.g., ABCD for row select signals, R1/R2 for data).
Power Cord Connection: The copper core diameter of the 5V power cable should be ≥1mm. The 220V power cable should use a 3-pin plug. Test Voltage: Use a multimeter to measure the power supply output voltage and ensure it is between 4.8-5.1V (adjust to 4.5-4.8V for lower brightness requirements).
II. Software Debugging and Display Control
Control Card Configuration
Connecting to a Computer: Connect the control card to a computer via a serial cable (RS232) or a USB-to-serial cable.
Software Settings:
Open the control card's accompanying software and set the screen parameters (width, height, and color mode).
Enter the display content (text, image, or animation). Animation playback supports a frame rate greater than 5 frames per second.
Example: To send the text "Welcome," you need to set the font, color, and scrolling speed.
Dynamic Display Implementation
Physical Button Control: Connect buttons to a microcontroller (such as the AT89S52) and programmatically light up the LEDs at specified locations and switch colors.
Mobile App Control:
Use a Bluetooth/Wi-Fi module (such as the ESP8266) to enable communication between the phone and the display. Develop an app to send commands and control screen display effects (such as flashing a red light or compressed image display).
Rotating Screen Effect:
Principle: 16 LEDs rotate via a motor, using persistence of vision to create text/graphics.
Key Points: Hall effect sensor speed synchronization, push-pull output to drive the LEDs, and adjustment of scanning speed to maintain stable font width.
III. Testing and Optimization
Unit Testing
Lighting Test: After powering on, check that all LEDs are illuminated. If some are not, use a multimeter to check for cable contact or a short circuit in the power supply.
Display Uniformity: Observe color consistency and adjust unit board brightness parameters (e.g., uniformly adjust brightness through the control card software).
System Integration
Multi-Screen Splicing: For example, to create a P2.5 indoor full-color screen (resolution 3840x1024), 45 receiving cards are connected via 8 network cables and the images are spliced using software.
Dynamic Effect Optimization: Adjust the animation frame rate (e.g., from 5 fps to 10 fps) to reduce lag.
IV. Application Scenarios and Expansion
Basic Applications: Outdoor advertising screens (single red/dual color), indoor information display screens (full color).
Creative Extensions:
Rotating Screens: Use 16 LEDs to display floating text, suitable for science and technology exhibition halls.
Transparent Screens: Use transparent LED modules to achieve both advertising and natural lighting on glass curtain walls.
Flexible Screens: Use flexible PCBs to create flexible LED strip screens.
Precautions: Safety First: Disconnect the power supply during assembly to avoid short circuits and component burnout.
Cooling Design: Full-color screens require fans or heat sinks to prevent brightness degradation due to high temperatures.
Waterproofing: Outdoor screens require adhesive tape on three sides of the PCB, ensuring an IP65 rating or higher.
Through the above steps, you can complete the entire process from hardware assembly to software debugging, enabling the LED screen to display static text, dynamic animations, and interactive control functions.