The dynamic display technology of 7-segment LED display is a display method that quickly scans and controls multiple digital tubes. This technology uses the visual persistence effect of the human eye to make multiple digital tubes appear to be displayed at the same time, but in fact they are lit up in sequence. The following is a detailed explanation of the dynamic display technology:
Basic Principle
The core of dynamic display lies in the control of bit selection and segment selection. Specifically, dynamic display is achieved through the following steps:
Bit selection control: Select the position of the digital tube that needs to be lit at present. For example, if there are 4 digital tubes, 4 bit selection lines are required to control which digital tube is lit.
Segment selection control: Control what number or character is displayed by the currently selected digital tube. This is achieved by controlling the lighting status of 7 segments (a, b, c, d, e, f, g).
Fast scanning: Light up each digital tube in turn by quickly switching the bit selection line. Because the switching speed is very fast (usually in milliseconds), the human eye cannot perceive this switching, resulting in the effect of multiple digital tubes displaying at the same time.
Advantages
Save I/O ports: Compared with static display, dynamic display requires fewer I/O ports. For example, displaying 4 digits only requires 8 I/O ports (4 bit selects + 4 segment selects), while static display requires 28 I/O ports (4 bits × 7 segments).
Simplify circuit: The overall circuit design is simpler due to the reduction of required I/O ports and drive circuits.
Reduced cost: Fewer components and simpler circuit design means lower manufacturing cost.
Disadvantages
Require dynamic refresh: Dynamic display needs to be refreshed continuously to maintain the display effect, otherwise it will flicker or display incompletely.
Increased complexity: The control logic is relatively complex and requires precise control of the scanning frequency and display time.
Implementation method
Dynamic display is usually implemented by a single-chip microcomputer or other microcontroller. The following is a basic implementation step:
Initialization: Set the direction and initial state of the I/O port.
Display data preparation: Convert the data to be displayed into the corresponding segment select code.
Scan cycle:
Select the position of the first digital tube (bit select).
Output the segment select code of the first digital tube.
Delay for a period of time (usually a few milliseconds).
Select the position of the second digital tube (bit selection).
Output the segment selection code of the second digital tube.
Repeat the above steps until all digital tubes are lit.
Continuous refresh: Repeat the scanning cycle continuously to maintain a stable display effect.
