How to Ballast an LED with a Series Resistor
Kiedy to ma zastosowanie
For indicator LEDs, a series resistor sets current given your supply and the diode forward drop. Use it as a first-pass check before you confirm with datasheets, temperature, and drive topology.
Narzędzie do użycia
Rezystor szeregowy z napięcia, Vf i prądu.
Otwórz Rezystor dla LED →Kroki
- 1Read target forward current and typical Vf from the LED datasheet (or lab guess for hobby parts).
- 2Enter supply voltage, Vf, and desired current in mA.
- 3Note the resistor value and power dissipation; pick the next standard value with margin.
- 4For networks, check series/parallel equivalents separately from a single ballast.
- 5For divider taps, remember loads draw current—unloaded Vout is an upper bound.
Przykłady
- 5 V supply, 2 V Vf, 20 mA target → ballast in the hundreds of ohms.
- Two resistors in parallel for equivalent R when you only have standard values.
Czego unikać
- Using peak PWM current as if it were DC average.
- Ignoring resistor power rating and overheating at small packages.
- Treating a loaded voltage divider like an unloaded calculator output.
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FAQ
Constant-current driver?
This flow is for resistive ballast. CC drivers need a different design checklist.
Multiple LEDs?
Series strings share current; parallel branches need their own limiting.
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