Page 429 - Robot Builder's Bonanza

398 COMMON ELECTRONIC COMPONENTS FOR ROBOTICS

Figure 31- 16 LEDs that display
more than one color have additional
connection points. The wiring of the
connections depends on the type of LED.
Shown here are several of the most
common.

• A two color (or bicolor) LED contains red and green LED elements (other colors are pos-
sible too, but the red/green combination is the most common). You control which color is
shown by reversing the voltage to the LED. You can also produce a yellowish- orange by
quickly alternating the voltage polarity.
• A tricolor LED is functionally identical to the bicolor LED, except that it has separate con-
nections for the red and green diodes. You can produce the intermediate color of
yellowish- orange by turning on both the red and green diodes at the same time.
• A multicolor LED contains red, green, and blue LED elements. You control which color
to show by individually applying current to separate terminals on the LED. These are also
called RGB LEDs.

There’s a bit of confusion as to what, exactly, constitutes bicolor and tricolor LEDs. Both
G can produce three colors: red, green, and yellowish- orange. The way they do it differs.
Compounding the confusion is that some sources call a multicolor LED a tricolor LED, because
it (rightly) contains three colors.

Common Anode or Cathode
To reduce the number of terminals coming out of the multidiode LED, all of the anodes, or all
of the cathodes, of each diode in the device are wired together. When all the anodes are com-
Common cathode Common anode bined, the LED is said to be common anode. And when all of the cathodes
are combined, it’s common cathode.
Which one you choose depends on what’s available and how the circuit is
designed. Common cathode is more common among multiple- color LEDs;
both common anode and common cathode are used in 7- segment and other LED displays.
Be sure to match the device with the circuit plans you’re using.

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