PAGE 096 OF 150 · DISPLAYS & INDICATORS
Scrolling Text Displays
Text shifts across a matrix one column at a time.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
How scrolling works
Text scrolls on a dot-matrix display by shifting the whole picture one column sideways every frame, so letters appear to slide across.
Steps
- Store each character as a small pattern, for example five columns for a 5 by 7 font.
- Join the characters of your message into one long buffer of columns.
- Show a window of the buffer, then move the window along by one column each frame.
Speed
A step every 50 to 150 milliseconds is comfortable to read. Slower scrolling is easier for long words.
Chained driver chips such as the MAX7219 let several 8 by 8 modules act as one wide sign.
REMEMBER
Scrolling is just shifting columns one step at a time.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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