LED series string calculator

The free browser path and the prepaid API share the same pure arithmetic module, so breadboard sketches and manufacturing tools never disagree on max_leds or ohms. API success items use prepaid KIT balance at $0.002; invalid inputs are not charged.

What a series LED string is and how max count is defined

Forward voltage is the per-LED conducting drop at the chosen current: red emitters often sit near two volts, white and blue closer to three volts, always taken from the datasheet at the intended milliamp level rather than a colour guess. Optional led_count lets you force a shorter string within that maximum when layout, colour mix or spare inventory dictates fewer diodes. Missing fields, non-positive voltages or current, non-finite numbers, and counts above max_leds all fail with invalid_input and are not billed. Identical JSON inputs always produce identical outputs because the path uses no network, no random seed and no wall clock.

Formulas, power rating, headroom errors and reading the response

Parallel multi-string ballast networks, constant-current LED drivers and PWM average-current models are outside scope—use a dedicated driver topology for those designs. After n is chosen—either the computed maximum or your explicit led_count—the engine multiplies n by per-LED forward voltage to obtain total_forward_voltage, subtracts that sum from supply voltage to obtain voltage_drop across the resistor, divides the drop by forward current to obtain resistance_ohms, and multiplies drop by current to obtain power_watts. The formula field restates n_max as the largest n with n times Vf less than Vs, R equals open parenthesis Vs minus n times Vf close parenthesis over If, and P equals If times that same drop, so UI copy can show the identities students write by hand. Recommended power watts is the smallest common commercial rating at or above twice the calculated dissipation, covering one sixteenth through fifty watt steps with a deterministic ceiling above the catalog, and power_margin is always two. When a single LED already meets or exceeds the supply, the request fails with invalid_input naming both voltages, because no series resistor can create headroom. When led_count exceeds max_leds, the message cites both integers so configurators can clamp or prompt the user. Successful responses echo the three primary inputs after stable rounding, plus max_leds, led_count, total_forward_voltage, voltage_drop, resistance_ohms, power_watts, recommended_power_watts, power_margin, formula and method led_series_string so downstream code can branch without sniffing shapes. Use resistance_ohms to pick the nearest E-series part on your own; this product returns the exact ohmic need, not a preferred-value table.

API usage, pricing, panels, education and practical limits

Call the free in-browser LED series string calculator for Christmas-light style indicator chains, Arduino multi-LED status bars, twelve-volt automotive accent strips and lab exercises without opening a spreadsheet. Keep requests small, document that current is in amperes, and treat the two-times wattage margin as a continuous-load rule of thumb rather than a full thermal model for high-power emitters. Send a JSON body with supply_voltage, forward_voltage and forward_current in volts and amperes; add led_count only when you already know how many diodes the layout will mount. Use the prepaid API when a parts configurator, IoT manufacturing tool, electronics homework oracle or CAD plugin needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with unit converters when datasheets list milliamps or millivolts, and with the single-LED resistor calculator when your search intent is only one diode rather than packing a string. Authors shipping SDKs can map max_leds, resistance_ohms and recommended_power_watts directly into BOM lines and form defaults that match what technicians stock in drawers.