# Current ratings and voltage drop for low voltage LED power supply cabling

01 May 2022 | all notes

WS2812B-controlled LEDs run on a supply voltage of 3.5 - 5.3V DC. Assuming you have a sufficiently strong 5V power supply, how much of an extension chord can you get away with between the supply and the LEDs?

As an example use case I had four NeoMatrix 8x32 RGB matrices where at any given time a total of 126 pixels were lit up, with RGB mixing never having more than two of the basic colors fully lit:

Max consumption = 1024 * 1mA per-pixel baseline + 126 * 40mA LED consumption ~ 6 Ampere total

Typical extension chords with a 5.5/2.1mm plug use either 20 or 22 AWG copper wires. For each type of wire there is a fixed voltage drop per Ampere per meter (see RapidTables voltage drop calculator). Maximum current rating depends on many other factors (type of insulation, number of cores etc), but if a cable’s rating is in the ballpark of the values below it should be alright:

AWG mm^2 Ohm / km DC Voltage drop (two-way total!) Current rating: very very conservative Typical Max. Current Load Rating (up to 3 cores) Single core
20 ~ .5 33 .066V per Ampere per meter 1.5A 5A 6A
22 ~ .3 53 .1V per Ampere per meter .92A 3A 5A

Product examples:

• BKL Electronic 5.5/2.1mm (072096 / 4011376104670) and 5.5/2.5mm (07298 / 4011376104687) 3m cable is rated at 7A

## 2.1mm or 2.5mm pin?

A 2.1mm receptacle:

• Will be able to have both types of plugs plug into it.
• Although some 2.5mm plugs have very springy inner contacts (so that they can make a solid contact with a 2.1mm pin), others do not, and, hence, can lose contact if the plug gets wiggled. But, at the very least, if all you have is a 2.5mm plug, you can get your device powered… but you may have to ensure that it doesn’t get bumped or moved. Probably the choice when you prefer user-friendliness over solid reliability.

A 2.5mm receptacle:

• Will not be able to receive a 2.1mm plug. This removes all doubt about which type of connector the user needs. They can only plug in the “correct” size.