PAGE 014 OF 150 · LED BASICS
Reading an LED Datasheet
Absolute maximum ratings are limits, not operating targets.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Where to start
A datasheet is the maker's list of what a part can do and what it must never be asked to do. Read it before choosing a resistor or driver.
Main sections
- Absolute maximum ratings: limits for current, reverse voltage, power and temperature. Never exceed them.
- Electrical and optical characteristics: forward voltage, brightness and wavelength, measured at a stated test current, often 20 mA.
- Forward voltage: minimum, typical and maximum values. Design with the typical and check the maximum.
- Luminous intensity: in mcd, or luminous flux in lumens for lamps.
- Viewing angle: where intensity falls to half, such as 30 or 120 degrees.
- Dominant wavelength or colour temperature: the colour of the light.
- Graphs and drawings: current against voltage, and package dimensions.
Habit to build
Always note the test conditions beside each number, because values change with current and temperature.
REMEMBER
An LED is a diode, so current flows through it in one direction only.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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