KEY FEATURES OF LED 7-SEGMENT 0.36″ CC 4-DIGIT:

• 4-digit 7-Segment display with common cathode (CC)
• 0.36″ high characters
• Floating decimal point
• 20 mA constant current, 100mA pulsed
• 12-pin package
• Red

Some common uses include displaying voltage and current on a variable power supply, use for a counter display or to keep an electronic score or as a reaction timer display. They are also popular for duplicating the look of some of the displays found in airplanes for creating home-built flight simulators consoles.

Theory of Operation:

Each digit of these displays have 7 separate LEDs comprising the 7 segments of the digit plus an 8th LED that functions as a decimal point.  The LEDs are labeled segment A thru G and the decimal point is DP.

The displays are common cathode (CC) type which means that all 8 of the LEDs in each of the 4 digits have their cathodes tied together and these are pulled to ground to enable that digit.   These connections are labeled D1 – D4 in the drawing.

To light a particular segment, the control (anode) pin for that segment is driven HIGH.  These 8 control pins should each have series current limiting resistors to prevent damage to the LED module or the MCU.  Instead of the control pins, current limiting resistors can be put on the pins connected to ground so that fewer are needed, but in that case the brightness of the display will vary depending on how many segments are lit at one time so that practice is not really recommended.

The connections for each of the individual segments such a ‘A’ are connected together in all 4 digits, so the displays are designed to be used in a multiplexed fashion unless you want all 4 digits to always show the same number or character which generally isn’t all that useful.

Multiplexing means that the ground connection (D1-D4 )for each of the displays is enabled sequentially by driving it LOW while the data for that particular digit is driven HIGH to light the desired segments on the 8 LED lines.  This is repeated for each of the digits very rapidly so that all of the digits appear to be operating continuously.

The pin-out shown here is as if you are looking at the face of the display.