7SegmentMultiplexing

Demonstration of segment multiplexing for a 7-segment display with an Arduino Uno/Nano.

Principle:

Only one segment at the same time is enabled
All digits uses the same segment at the same time
Every digit, where the current segment should be shown, is enabled
On every display update the next segment will be enabled. If the last segment is reached the next segment will be the first segment.

This technic could be used to drive a 7-segment display with a common anode or cathode (for example 4041AH):

directly by an Arduino Uno/Nano and
without a special display controller and
without too much current on microcontroller I/O-pins (Max. 40mA per I/O-pin would be allowed for an ATmega328P and 200mA for all I/O-pins in sum. We will use only ~11mA per I/O-pin and in sum 11mA*"Number of digits" due segment muliplexing, for example 44mA for a 4 digit display)
with only one current limiting resistors per digit and
without brightness flickering depending on how many segments of digit are used

Disadvantages:

We use use only 1/8 of the maximum possible brightness of the display
We have to update the display every ~2ms to avoid flickering (for example by timer2)