PAGE 059 OF 150 · WIRING LEDS
Voltage Drop on Long Wire Runs
Thin or long wire loses voltage before the LEDs.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Why voltage drops
Wire has resistance, so a long run loses voltage equal to current times resistance. LEDs far from the supply get less voltage and appear dimmer.
Example
A 12 V strip draws 3 A, supplied through 5 m of 18 AWG wire. The round trip is 10 m, about 0.21 ohms, so the drop is roughly 0.63 V, around 5 percent.
Reducing it
- Use thicker wire.
- Shorten the run.
- Feed power from both ends.
- Use a higher voltage, such as 24 V, so the same power needs half the current.
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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