LED Tape PSU and Voltage-Drop Run
Total load, recommended PSU size, and end-of-run voltage of a constant-voltage LED strip.
Example
You enter
- Strip power (W/ft) 4.4
- Run length (ft) 16
- Supply voltage (V, 12 / 24) 12
- Round-trip resistance (ohm/ft) 0.05
- PSU headroom (%) 20
- Acceptable end drop (%) 10
You get
- Load w 70.4
- Psu w 88
- End voltage v 9.65
Checked against published worked examples from: Constant-voltage LED strip loading and voltage drop.
Details, formula, and sources
ScopeWith a too-long flag when the far end dims. Oversizing the PSU does not fix the drop -- power-inject or feed both ends; 24 V tape reaches roughly double a 12 V run.
Formula or tableload = power_per_ft x length; psu = load / (1 - headroom); current = load / voltage; end_drop = current x (resistance_per_ft x length) / 2; end_voltage = voltage - end_drop.
Source and editionConstant-voltage LED strip loading and voltage drop, by name.
Free accessStandard low-voltage LED-strip loading relation; the strip datasheet governs.
What governsEstimate. AHJ and licensed professional govern.
API field namespower_per_ft_w, run_length_ft, supply_voltage_v, resistance_per_ft, headroom_pct, drop_tolerance_pct, load_w, psu_w, end_voltage_v
- Uniform-load drop end-fed uniform load drops half the full-current voltage (current x R / 2)constant-voltage LED loading