While testing some newly acquired warm white 12V LED tape (5050 and 3528) I noticed that the current for the whole 5m length did not tally with the expected current based on the type of LED and value of the series resistor.
This appears to be down to a modest voltage drop along the run that results in the LEDs at the far end getting a lot less current than the ones at the power supply connection point. It’s not a high voltage drop, but because the LEDs tend to have a fairly narrow forward voltage range, most of the difference occurs across the resistors, and even half a volt makes a huge difference to the current for a given resistor value.
It follows that it’s better to use short lengths of this tape, and if you are needing a long run then divide it down into shorter individually fed sections.
