PAGE 018 OF 150 · COLOURS, SIZES & TYPES
Blue LEDs
Blue LEDs need roughly three volts and are the basis of white LEDs.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
About blue LEDs
Blue LEDs use indium gallium nitride and emit around 450 to 470 nm. Their photons carry more energy than red or green ones, which is why blue needs a higher forward voltage of about 3.0 to 3.4 V.
Why blue matters
- Blue chips are the starting point for most white LEDs.
- Together with red and green they make full-colour RGB displays.
- Blue light is strong for its brightness reading, so it can look glaring in dark rooms.
Practical advice
Use at least a 5 V supply with a resistor. Use lower current than for red if the LED looks dazzling, and avoid pointing very bright blue LEDs at the eyes.
REMEMBER
Colour is set by the semiconductor material, not by the plastic lens.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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