LED Calculator

1. Basic LED Characteristics

Light Emitting Diodes (LEDs) are current-driven devices that convert electrical energy into light. Key parameters include forward voltage (Vf), forward current (If), and luminous intensity. The relationship between current and light output is approximately linear within the operating range.

Forward voltage varies by color and type
Current determines brightness
Maximum ratings must not be exceeded
Temperature affects performance

2. Current Limiting

Current limiting is essential for LED operation. The resistor value is calculated using:

R = (Vs - Vf) / If
where:
R: Resistor value (Ω)
Vs: Supply voltage (V)
Vf: LED forward voltage (V)
If: Desired forward current (A)

3. Power Considerations

Power calculations are important for both LED and resistor selection:

LED power: P_led = Vf × If
Resistor power: P_r = (Vs - Vf) × If
Total power: P_total = Vs × If
Use resistors rated at least 2× calculated power

4. LED Layout Calculations

How to calculate LED lighting requirements for a room:

Parameter	Formula	Example
Number of Downlights	N = (Area × Lux) / (LPW × η)	20m² × 400lx / (100 × 0.85) = 9.4
Light Spacing	D = √(Area/N)	√(20/10) = 1.4m spacing

5. LED Driver Calculations

How to calculate LED driver size and wattage:

Driver Size Calculation:
- Total LED power = Number of LEDs × Power per LED
- Driver wattage = Total LED power × 1.2 (safety margin)
- Driver current = Total power / LED string voltage
- Consider efficiency losses (typically 85-90%)
Voltage Requirements:
- Series string voltage = LEDs × Vf per LED
- Account for voltage drop in wiring
- Consider temperature effects
- Allow for dimming range

6. LED Power Consumption

How to calculate LED power consumption and energy savings:

Calculation	Formula	Notes
Daily Usage	kWh = W × Hours × Days / 1000	Monthly × 30 for monthly
Energy Cost	Cost = kWh × Rate	Use local electricity rate

7. Thermal Management

Thermal considerations are crucial for LED reliability:

Junction temperature limits
Thermal resistance path
Heat sink requirements
Ambient temperature effects

8. Series/Parallel Configuration

Multiple LED arrangements require special consideration:

Series: Same current, voltages add
Parallel: Same voltage, currents add
Mixed: Combination calculations
Current balancing in parallel

9. Design Guidelines

Follow these guidelines for reliable LED circuit design:

Include current derating (typically 80%)
Consider temperature effects
Use appropriate power ratings
Implement proper heat management
Verify voltage tolerances
Test under actual conditions

10. LED Power Supply Calculations

How to calculate power supply requirements for LED circuits:

Parameter	Formula	Example
LED Strip Power	P = V × I × L/m × Length	12V × 1.2A/m × 5m = 72W
Current Draw	I = P/V	72W/12V = 6A
Battery Size	Ah = (I × Hours)/0.8	6A × 4h/0.8 = 30Ah

Understanding LED Circuit Design