Engineering & Hardware Utilities
Precision calculators for PCB trace geometry, passive networks, RF microstrip impedance, and MCU peripherals based on IPC standards.
LED Series Resistor Calculator
Forward voltage drop, source voltage, and operating current calculation
LED Circuit Inputs
Current LimitResistor Sizing & Rating
Mathematical Formula & Engineering Rules
Presistor = ILED2 × R = (Vsource - Vforward) × ILED
Worked Engineering Example
Target: Drive a high-brightness Blue LED (Vf = 3.2V, 20mA) from a 5V supply.
- Voltage drop across resistor: 5.0V - 3.2V = 1.8V.
- Ideal resistor: 1.8V / 0.020A = 90 Ω.
- Standard E24 value: 91 Ω (resulting in 19.8 mA current).
- Power dissipation: 1.8V × 0.0198A = 0.035W → use standard 0.125W (1/8W) or 0402 SMD resistor.
Frequently Asked Questions
Q1:
Explore Sibling Calculators
Trace Width Calculator
Conductor width, cross-section area, resistance, and temperature rise
Voltage Divider
Loaded vs. unloaded output calculations and standard E24 resistor pairing
SMD Code Decoder
3-digit, 4-digit, and EIA-96 precision resistor marking decoding
Battery Life Estimator
Battery capacity, active/sleep duty cycles, and operating lifespan
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