PAGE 048 OF 150 · WIRING LEDS
Series-Parallel Arrays
Several equal series strings can be paralleled.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Combining both
A series-parallel array uses several identical series strings wired side by side, each with its own resistor. It gives many LEDs from one supply with good efficiency.
Example
On 12 V, take four strings of three red LEDs. Each string needs (12 − 6) ÷ 0.02 = 300 ohms. Total current is 4 × 20 mA = 80 mA.
Benefits
- If one string fails, the rest keep working.
- Each string's current is set separately, so they stay balanced.
Keep the strings identical in LED type and resistor value.
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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