Results
Resistor Value
0 Ω
Standard value: -
Power Dissipation
0 W
Recommended: -
Current Through LED(s)
0 mA
Voltage Drop
0 V
Circuit Diagram
Calculation Formulas
The resistor value is calculated using Ohm's Law:
\( R = \frac{V_{supply} - (V_{f} \times N)}{I_{f}} \)
Where:
- R = Resistor value in ohms (Ω)
- Vsupply = Power supply voltage in volts (V)
- Vf = LED forward voltage in volts (V)
- N = Number of LEDs in series
- If = LED forward current in milliamps (mA)
Power dissipation in the resistor is calculated as:
\( P = I^2 \times R \)
Resistor Selection Guide
When selecting a resistor for your LED circuit:
- Always choose a resistor with a power rating higher than the calculated dissipation
- Common resistor power ratings: 1/8W, 1/4W, 1/2W, 1W, 2W, 5W
- For most low-power LEDs, 1/4W or 1/2W resistors are sufficient
- Standard resistor series:
- E12 (±10%): 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82
- E24 (±5%): Adds intermediate values between E12 values
- E48 (±2%) and E96 (±1%): Even more precise values
LED Characteristics
Typical LED forward voltages by color:
| Color | Forward Voltage (V) | Typical Current (mA) |
|---|---|---|
| Red | 1.8-2.2 | 10-20 |
| Yellow | 1.9-2.4 | 10-20 |
| Green | 2.0-3.0 | 10-20 |
| Blue | 2.8-3.6 | 10-30 |
| White | 3.0-3.6 | 15-30 |
| Infrared | 1.2-1.8 | 20-50 |
Always check your LED's datasheet for exact specifications.