CIRCUIT PARAMETERS
V
V
mA
CIRCUIT DIAGRAM
CALCULATION SHEET
Recommended Resistor
150 Ω
E24 Series Standard Value · Calculated: 150.0 Ω
Actual Current
0.0 mA
(0% of target)
Power Dissipation
0.06 W
Min Power Rating
0.125 W
Efficiency
40.0%
Calculation Steps
- 01LEDs in series: 1
- 02Total LED voltage: 2 V × 1 = 2 V
- 03Voltage across resistor: 5 V - 2 V = 3 V
- 04LED current: 20 mA = 0.02 A
- 05Required resistance: R = V / I = 3 / 0.02 = 150.00 Ω
- 06Closest E24 standard value: 150 Ω
- 07Actual current with 150Ω: 0.0200 A = 20.0 mA
- 08Power dissipation: P = V × I = 3 × 0.0200 = 0.060 W
- 09Recommended power rating: 0.125 W (2x safety margin)
- 10Efficiency: 0.040 W / 0.100 W = 40.0%
- 11⚠️ Low efficiency - consider using constant current driver instead
REFERENCE — LED RESISTOR GUIDE
Formula:
R = (Vsupply - VLED) / ILED
Typical LED Values:
- • ● Red: 1.8-2.2V @ 20mA
- • ● Green: 2.0-2.4V @ 20mA
- • ● Blue: 3.0-3.4V @ 20mA
- • ● White: 3.0-3.4V @ 20mA
Power Rating:
Use at least 2× calculated power for safety margin. Standard ratings: ⅛W, ¼W, ½W, 1W