A multiplexed display in digital electronics refers to a technique used to drive multiple display elements, such as LEDs or segment displays, using a smaller number of control signals or connections. It allows for the efficient use of resources and reduces the complexity of the driving circuitry.
In a multiplexed display, the display elements are organized into a matrix or a series of rows and columns. Each element, often referred to as a segment, is controlled by a combination of the row and column signals. By rapidly cycling through the rows and selectively activating the desired segments in each row, the illusion of a static display is created.
One common example of a multiplexed display is a 7-segment display used to show numeric digits. A typical 7-segment display consists of seven individual segments arranged in the shape of a figure-eight, with an additional eighth segment for a decimal point if needed. Each segment can be independently turned on or off.
To multiplex a 7-segment display, a microcontroller or other driving circuitry rapidly cycles through the digits of the display. It activates one digit at a time by driving the appropriate combination of row and column signals. For example, to display the number “1,” the microcontroller would activate the segments necessary to form the digit “1” in the first row, then quickly switch to the next row and activate the segments for the next digit to be displayed.
By cycling through the rows fast enough, typically at a frequency above the human eye’s perception, the display appears as if all the digits are continuously lit. This technique reduces the number of control signals required to drive the display. For a 4-digit 7-segment display, instead of needing 32 control signals (4 rows × 8 segments), only 11 signals (4 rows + 7 segments) are required.
Multiplexed displays are commonly used in applications where there are multiple display elements, such as digital clocks, calculators, digital meters, and many other devices where numerical or alphanumeric information needs to be shown. The technique allows for efficient utilization of resources while maintaining a visually appealing display.
Multiplexed display is a technique used in electronic visual displays to update the screen more quickly than would be otherwise possible. Here are some key points about multiplexed displays:
- In a multiplexed display, the individual pixels or display elements are not continuously illuminated. Instead, they are rapidly switched on and off in a predefined sequence or pattern.
- For example, in a simple multiplexed 7-segment LED display, each segment is only illuminated briefly as it takes a turn rather than all segments staying lit at once. This switches which segments are active very rapidly to create the appearance of all being on simultaneously.
- This allows the display to update the image faster than if all elements had to be driven continuously. With proper timing and sequencing, the flickering is imperceptible to the human eye.
- Common types of multiplexing include row/column multiplexing in LED and LCD displays, where rows or columns are activated one at a time to draw the full screen image.
- Multiplexing enables features like animations, video playback and responsiveness on simple displays that wouldn’t otherwise have the processing power or connection bandwidth to do so.
- The tradeoff is increased complexity of the display driver circuitry required to properly sequence and time the on/off switching of individual pixels or segments.