Voltage drop and maximum run length, explained

The copper conductors inside a strip have resistance. As current flows along the run, voltage falls, so the LEDs at the far end receive less than the LEDs at the feed end. The result is a gradient: the start is bright, the end is dimmer and slightly warmer or cooler depending on the bin.

For the same power per metre, a 24 V strip draws half the current of a 12 V strip. Lower current means a smaller voltage drop over the same copper, which is why 24 V runs are longer before the gradient becomes visible.

The table on a datasheet is a guideline based on the strip's copper and the acceptable drop at the end of the run. Typical figures for a standard 24 V line at around 10 W/m sit near 10 m from a single feed; the same line at 12 V is closer to 5 m.

High-output strip shortens these limits, because current rises with power. A 20 W/m line will show a visible gradient well before a 10 W/m line of the same construction.

Feeding both ends halves the current through each half of the strip's copper and visibly reduces the gradient. For longer runs, a loop feed or power injection at intervals is the usual solution in coves and facades.

When injecting power, join the 0 V of every feed point together. Leaving separate 0 V paths can cause flicker or uneven brightness, particularly with dimmers and pixel control.

Show each run as a separate line with its own feed, the driver location, the total load per driver and the length of the feed cable. This makes the drop calculation possible before the order, rather than on site.