PAGE 021 OF 150 · COLOURS, SIZES & TYPES
White LEDs
Most white LEDs are blue chips coated with a phosphor.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
How white LEDs work
A typical white LED is a blue chip coated in phosphor that converts part of the blue light to yellow and red. A second approach mixes separate red, green and blue chips, which allows adjustable colour but is more complex.
Electrical details
Forward voltage is usually 3.0 to 3.4 V, like blue, so power from 5 V or more with a resistor.
Quality measures
- Colour temperature in kelvin describes warm or cool tone.
- Colour rendering index (CRI) shows how naturally objects appear; 80 is common and 90 or more is very good.
- Binning sorts LEDs by colour and brightness, and mixing bins can show visible differences.
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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