# WS2811 series: power consumption and voltage drop

I recently bought some WS2811 LED strips (these). I intend to connect 6 in series (6 * 50 = 300 leds), and I have some questions.

In the datasheet and on the Amazon page it is written that each LED can consume 0.3W (0.3W / 5V = 60mA). Since I have to power 300 LEDs I have calculated that the consumption in amperage will be about ~18A (300 LEDs * 60mA). To have some headroom I bought a 4-7V 20A adjustable power supply.

Now I tested my setup and I realized that the LEDs farthest from the power supply gradually became less bright and then turned off due to voltage drop, so I intended to pass a wire parallel to all the strips (the green one in the image). The length of this cable should be around 21m (each strip is 3.5m long).

So my questions are:

• With this setup, will I be able to turn on all the LEDs at maximum brightness?
• How thick does the parallel wire have to be to support 18A?
• Just to be clear, WS2811 is 12V, and WS2811B is 5V. I have found it is advisable to undervolt these LEDs because full brightness is very 'washed out'. Lower voltages give much better colour. Also external power is also advisable. While you can power small strips directly from an MCU, these LEDs can easily overload tiny MCU voltage regulators. Commented Jun 22, 2022 at 16:01

I would start by simply running one pair of 18 gauge wires to each end of your strip. Then combine the two "+" 18-gauge wires at the power supply. Same with the two "-" wires. If both 18-gauge wires don't fit to the power supply, connect them to a 10 to 12 gauge wire and run that fatter wire to your power supply.

If your big power supply cannot handle a 10 to 12 gauge wire, it may not be designed very well. The 12-gauge should be the minimum for that amperage without overheating.

If you see dimming in the middle, run another pair of 18-gauge wires to the middle of your strand.

Here is an example... All LEDs are less than 100 LEDs from a power drop.

• Wikipedia says 10A for 18-gauge wire at 60°C rated wire. en.m.wikipedia.org/wiki/American_wire_gauge See source in footnotes of the Wikipedia link. What source says 2.3A? Commented Nov 21, 2021 at 19:18
• Different sources, just googled awg ampasity. May be they wrong. The OP intention to use chain connection, not star. So current max 18A. Commented Nov 21, 2021 at 19:51
• That's why I told him to use star. Commented Nov 21, 2021 at 20:52
• @GTElectronics Thanks for the reply, unfortunately I cannot use a star layout, I have to chain them
– Emax
Commented Nov 21, 2021 at 21:44

60 mA each LED consume at full brightness. If you need to use all of them close to it, the parallel run of feeder is essential. Size of parallel wires is depends of the way, you are connecting. For instance, the star, each pairs of wires running to each pease of string. Or chain. First run thick wires, next runs smaller. Drop voltage is important, minimum supply voltage for WS2811 you can get from datasheet. And it may be calculated, simply Ohm's law. But my suggestion, try to test it with lower brightness, may be you do not need it full. Maximum brightness just give you white or yellowish color. One color full brightness will consume only 20 mA. And you do not have to connect +5V between strips, just data and ground.

• On the WS811 datasheet it says: It is a constant-current three-channel driver that operates on 4.5 ~ 5.5 V, with absolute maximum ratings of 6 ~ 7 V. So the minimum voltage should be 4.5V. I'm planning to connect them in a chain way
– Emax
Commented Nov 21, 2021 at 17:52
• Use 2.5 mm2 from power supply to first connection and from first to second. The rest could be 1.5mm2 Commented Nov 22, 2021 at 1:07

Use use 14-16awg wire to run power to your first pixel. Run another 14-16awg wire parallel to your led strings. Tap the power into your LEDs every 100 pixels. Although they can handle .06 amps, run them at .03-.04. You don’t get much more out of your pixels when you push them at .06 amps. And they’ll last longer. This will also keep you power supply from working too hard. You shouldn’t really drive power supplies past 80% of their capacity. If you do run them at .06 amps, get a 29 or 30 amp supply.