Assumes I_f = 20 mA. Standard E12 resistor values shown — round up to the next standard value in practice.
Resistor @ 20 mA
| LED color (V_f) | 3.3 V | 5 V | 9 V | 12 V | 24 V |
|---|---|---|---|---|---|
| Red (1.8 V) | 75 Ω (30 mW) | 160 Ω (64 mW) | 360 Ω (144 mW) | 510 Ω (204 mW) | 1,110 Ω (444 mW) |
| Orange (2.0 V) | 65 Ω (26 mW) | 150 Ω (60 mW) | 350 Ω (140 mW) | 500 Ω (200 mW) | 1,100 Ω (440 mW) |
| Yellow (2.1 V) | 60 Ω (24 mW) | 145 Ω (58 mW) | 345 Ω (138 mW) | 495 Ω (198 mW) | 1,095 Ω (438 mW) |
| Green (3.2 V) | 5 Ω (2 mW) | 90 Ω (36 mW) | 290 Ω (116 mW) | 440 Ω (176 mW) | 1,040 Ω (416 mW) |
| Blue (3.2 V) | 5 Ω (2 mW) | 90 Ω (36 mW) | 290 Ω (116 mW) | 440 Ω (176 mW) | 1,040 Ω (416 mW) |
| White (3.2 V) | 5 Ω (2 mW) | 90 Ω (36 mW) | 290 Ω (116 mW) | 440 Ω (176 mW) | 1,040 Ω (416 mW) |
| UV (3.5 V) | — | 75 Ω (30 mW) | 275 Ω (110 mW) | 425 Ω (170 mW) | 1,025 Ω (410 mW) |
Notes
- Formula: R = (V_supply − V_f) / I_f.
- For long strings, consider a constant-current driver instead of a resistor.
- Dissipation values in parentheses — pick a resistor rated at least 2× for margin.
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