PAGE 046 OF 150 · WIRING LEDS
LEDs in Series
Forward voltages add up along the chain.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
How series wiring works
In a series string the LEDs are connected end to end, anode to cathode. The same current passes through every LED, and their forward voltages add up.
Example
Three red LEDs at 2 V each total 6 V. On a 12 V supply the resistor takes the remaining 6 V, so at 20 mA R = 6 ÷ 0.02 = 300 ohms.
Points to know
- The supply must be higher than the total forward voltage.
- If one LED fails open, the whole string goes out.
- One resistor serves the whole string, which wastes less energy than separate resistors.
REMEMBER
In series the same current flows through every LED.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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