Electronic Components
LED Series String Calculator
This calculator evaluates maximum LEDs per string for a single electronic components scenario. It uses available LED voltage and forward voltage per LED and shows the equation behind the displayed value.
Inputs for this calculation
Do not mix values recorded under different conditions.
Input notes
Use data-sheet values at the intended voltage, current, frequency, and temperature. A source note beside each entry makes the result reproducible.
Values used below a division bar must stay positive. Use the displayed unit for every field and document conversions separately. For the companion total LEDs calculation, open LED Array Configuration Calculator.
- Available LED voltage
- Default example: 21 V. Enter available LED voltage in V.
- Forward voltage per LED
- Default example: 3 V. Enter forward voltage per LED in V.
Formula used on this page
Here, Maximum LEDs per string is obtained from count = floor(available voltage ÷ forward voltage). Its variables correspond to Available LED voltage and Forward voltage per LED.
The initial scenario returns 7 LEDs. Re-enter field data before using the answer in a design or comparison.
Find the maximum whole LED count supported by the available voltage. For a downstream series resistance value, open LED Resistor Calculator.
Transferring the result
Archive available LED voltage and forward voltage per LED with maximum LEDs per string. Identify the instrument, rating, or assumption behind each entry.
Pass maximum LEDs per string with all available digits during downstream arithmetic. Keep a separate displayed value if reporting precision differs.
Interpreting the answer
The primary answer, Maximum LEDs per string, describes only the entered scenario. Compare it with voltage rating, current rating, dissipation, tolerance, and transient stress.
Store the measurement state and conversion notes with the answer.
Common entry mistakes
Mixing nominal and measured data is a common source of error.
Compare the magnitude with a quick independent estimate.
Assumptions and limitations
Reserve additional voltage for the current regulator and worst-case LED forward voltage.
The equation does not include pulse ratings, frequency behavior, package temperature, and layout. Document which effects were checked elsewhere in the analysis.
Keep nominal component markings separate from measured operating values.
Common questions before using the result
How should I prepare the LED Series String inputs?
Choose entries that describe the same case. Use data-sheet values at the intended voltage, current, frequency, and temperature.
What assumptions affect Maximum LEDs per string?
The result follows the displayed variables. Check bias dependence, ESR, leakage, saturation, and self-heating separately.
What can cause a different maximum LEDs per string reading?
Recheck units and operating state before investigating parasitics, layout inductance, tolerance stack-up, switching edges, and thermal resistance.
How do I run a useful sensitivity check?
Change one uncertain entry at a time and preserve the baseline. Use data-sheet values at the intended voltage, current, frequency, and temperature.
Does LED Series String Calculator choose a final rating?
No. Compare the value with voltage rating, current rating, dissipation, tolerance, and transient stress and apply relevant equipment and installation requirements.