PAGE 051 OF 150 · WIRING LEDS
Maximum LEDs on a 12 V Supply
Divide usable voltage by one LED's forward drop.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Leave headroom
The resistor needs a reasonable voltage to regulate current, typically at least 10 to 20 percent of the supply, and more if the supply varies.
Typical limits on 12 V
- Red or yellow at about 2 V: up to 5 LEDs, leaving 2 V for the resistor.
- White or blue at about 3.2 V: up to 3 LEDs, using 9.6 V and leaving 2.4 V.
- Four white LEDs need 12.8 V, which exceeds 12 V.
Vehicle supplies
A running vehicle can reach about 14 V, so allow for that. More LEDs per string need a well-regulated supply.
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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