Each of the seven segments (A – G) and the decimal point (P ) are connected in the same way as an LED, in series with a resistor.
One of the Com (common) ports are connected to ground . This acts as a single cathode for all of the LEDs in the seven segment display.
Light Emitting Diodes (LEDs) are semiconductors that emit light when a current is applied to them. They are comparatively much more energy efficient, when compared to lighting alternatives (E.g filament bulbs), but are generally considerably more expensive.
As with any other didode, LEDs have an anode and a cathode. However, the reverse breakdown voltage is much lower. In addition to this, a resistor is needed in series, in order to limit the rate at which current flows through the LED.
RGB LEDs consist of three LEDs (Red, Green, and Blue). They’re all self-contained within the same plastic casing and share either a common anode, or a common cathode.
Due to the differences in electrical characteristics, a larger resistor is needed in series with the red than that of the green and blue.
Approximate values of: 150Ω, 100Ω, 100Ω are suitable with a 5 volt supply.