Driving a 7 Segments Display

Cover image

The video above, illustrate how I wrote a library that drives the 2 displays without a driver, just using the micro controller pins.

The video starts in a slow motion fashion so you can see every segment lit up individually, then it gets faster and faster, until it reaches normal speed and the digit 3 seems still. This technic is called multiplexing. Then it shows how two digits can be seem as fully lit up, but in reality only a single segment is lit at once. At normal speed it gives the impression that a 88 is being displayed. This technic is called multiplexing.

A multiplexed display has several advantages compared to a non-multiplexed display:

  • fewer wires are needed, paralleling the displays except the common wire;
  • simpler driving electronics can be used (single resistor per display, instead of one for each segment);
  • both lead to reduced cost;
  • reduced power consumption (since there's only a single segment powered at time);

The code for just the display multiplexing can be found here: https://github.com/victornpb/ledDisp

Or you can find the complete code for this project at the final steps.