Dim or colour-shifted strip ends almost always come from topology, not the driver. Using one 24 V 14.4 W/m strip we calculate the end-of-line voltage drop for single-end, both-end and star wiring, with a 5/10/15 m table and a multimeter test to pick the right method.
A strip is itself a resistive conductor. A 5 m strip and a 15 m strip on the same driver and the same wiring can look visibly different at the end - the cause is topology, not the driver. This article runs the three common methods on one strip.
The one-sentence rule: measure the end voltage first, then decide whether to rewire
Strip copper foil has resistance, and current through it drops voltage. How bad the drop is depends on two things: how long the strip is and where the current enters. The driver outputs 24 V; if the strip end reads 22 V versus 20 V, the eye sees the difference. Always measure the end voltage before talking about a bigger supply.
What the three topologies look like
Single-end, both-end and star feed: different current paths, very different end drop
Single-end feed: the supply connects one end only; current flows the whole foil length to the far end. Longer means more drop at the end. Easiest to do, easiest to fail.
Both-end feed: both ends of the strip connect to the supply positive (and negative likewise); current converges from both ends, so the worst point becomes the middle and the effective length halves.
Star feed: each strip section gets its own lead from the supply, independent of the others. Drop is set by the lead wire size you choose, not by the strip foil. The cost is more cabling.
Same strip, end voltage under the three methods
Take a common 24 V, 14.4 W/m constant-voltage strip; foil one-way resistance at a typical R' about 0.05 ohm/m (2 oz process runs 0.04-0.06; confirm by measurement). Current density 0.6 A/m.
End drop for single-end feed, where current falls linearly along the strip:
dU about I_m x R' x L^2 / 2
I_m current per metre (A/m)
R' strip foil one-way resistance (ohm/m)
L strip length (m)
Strip length
Single-end drop
End voltage (from 24 V)
Deviation
5 m
0.38 V
23.6 V
1.6%
10 m
1.50 V
22.5 V
6.3%
15 m
3.38 V
20.6 V
14.1%
Both-end feed moves the worst point to the middle and cuts the end drop to about one quarter: the same 15 m strip drops only about 0.84 V (22.3 V, 3.5% deviation), far better than 3.38 V single-end.
The most useful line: within 10 m single-end is fine, beyond 15 m single-end will dim and you must switch to both-end or star. Do not reach for a higher-power supply first - it still outputs 24 V and cannot fix the drop across the strip foil.
Using a multimeter to pick the method
This step saves a lot of pointless supply swaps.
Measure at the strip input, call it V_in (should be near 24 V)
Measure at the strip far end, call it V_end
Deviation = (V_in - V_end) / V_in x 100%
Deviation 3% or less: no visible difference, leave it
Deviation 3%-8%: switch to both-end feed, no supply change needed
Deviation over 8% or colour shift visible end to end: switch to star feed, or split one long strip into two shorter ones each on its own supply
Colour shift is harder to forgive than brightness: at the strip end the lower voltage, together with the LED Vf temperature coefficient, shifts colour. You measure voltage, but you fix brightness and colour together.
Wiring and acceptance checklist
Take watts per metre from the strip spec, derive current per metre (24 V, 14.4 W/m is about 0.6 A/m)
Estimate foil resistance R' (no data, use 0.05 ohm/m conservative; better, measure a section with a four-wire meter)
Apply dU about I_m x R' x L^2 / 2 and require deviation 3% or less
For long strips prefer both-end feed (drop to about one quarter); if not enough, go star
Accept by measuring input and far end: deviation 3% or less and no visible colour shift
For supply sizing check the total power and current with the LED driver sizing calculator; the same calculator handles parallel-loop current. Constant-voltage units such as H01, H07, K01 and S01 follow the same foil-drop rule. On long-strip projects settle both-end or star feed at drawing stage rather than after installation. For wiring and application fit across all six dimming methods see the dimming comparison table.
Strip ends dim or colour-shifted? Send us the strip voltage, watts per metre, total length and current wiring and we will work out the end drop and propose both-end feed or an extra supply. Contact →