I'm having issues trying to power my 5 meter 300 led 60 led per meter strip and I'm using the sp105e magic controller to control them.

I cannot get them to light up correctly. I have a 4.5V 100mA power supply and the LEDs flash very dim for 1 second then nothing.

I tested with a 12V 833mA power supply and I at least got to see them on, but could only use them at less than half brightness. The power supply was also very warm.

The LEDs themselves seemed warm to the touch but I assume that is normal. If these power supplies aren't right, how do I figure out which one I should use? What power/voltage/current do I need to produce full brightness?

I will not run them at full brightness but want them to be capable. I don't want to destroy my LEDs or burn my house down. Any help from you guys would be greatly appreciated!

  • 3
    \$\begingroup\$ Let's say that each LED will draw 10 mA. Then the entire strip will draw 300 x .01 amps, or 3 amps. If the maximum draw is 20 mA per LED, that will be 6 amps. You have a 4.5 volt/ 100 mA controller. Do you think there might be a problem, trying to draw 3-6 amps from this? \$\endgroup\$ Commented Sep 16, 2018 at 4:41
  • \$\begingroup\$ please provide a link to the LED strip data sheet \$\endgroup\$
    – jsotola
    Commented Sep 16, 2018 at 4:42
  • 1
    \$\begingroup\$ You should provide a link to the specific strip you're using, but as a preliminary, a 5050 ws2812b strip of 60 LEDs needs 2.9A for full brightness at 5V, so you need 15A@5V for your arrangement. \$\endgroup\$
    – K H
    Commented Sep 16, 2018 at 4:54
  • \$\begingroup\$ Did you understand my answer? \$\endgroup\$ Commented Sep 16, 2018 at 20:31
  • \$\begingroup\$ i did provide a link to the strip \$\endgroup\$ Commented Sep 17, 2018 at 2:38

3 Answers 3


I think it's time you read the datasheet for the WorldSemi WS2812B.

You have to supply them with 5.0 Volts. 12 Volts will likely kill them, although because there's so many of these in parallel across the bus on such a long & high-density string, you might've gotten lucky and had the 12V rail sag so much that they didn't see 12V for very long.

At full brightness (R, G & B LEDs all 100% on) they'll draw 60mA, each. So your 5V 100mA power supply won't power more than 1 of these WS2812Bs before buckling. If that 5V/100mA PSU came with this bundle, it's probably only meant to power the controller you mention.

For a 300 x WS2812B strip you'll need a 5V 18 Amp PSU, and you'll need to connect this to at least both ends of the strip, and possibly half way along too, with THICK wires (AWG16 or thicker) because of the voltage-drop you'll get from an 18 Amp draw of a 5V rail along such a long strip with so many diodes.

WS2812B strips are utterly ubiquitous, and powering them has been documented ad nauseam all over the net. Google is your friend.

enter image description here

  • \$\begingroup\$ here is the exact link to the strip i have. ebay.com/itm/… \$\endgroup\$ Commented Sep 16, 2018 at 7:28
  • \$\begingroup\$ the power needs to run through the controller and into the strip. i cant just power the strip. they need a driver to control them. \$\endgroup\$ Commented Sep 16, 2018 at 7:32
  • \$\begingroup\$ you have 2 choices: feed 5 Volts (from a PSU capable of 18Amps) into the controller and discover, at best, that the brightness at the entry end is quite a lot better than the brightness at the far end, and at worst some LEDs just won’t work, or, resign yourself to the fact that this shit from Alibaba isn’t designed or made to work well, and wire it like the diagram I’ve added to my answer. The 1 5V PSU powers, via separate wires (a) the controller (only thin wired needed) and both ends of the strip (thick wires needed). And the 1 D wire out of the controller to its input end. \$\endgroup\$ Commented Sep 16, 2018 at 16:45
  • \$\begingroup\$ also, that SP105 controller is made for multiple strips that are driven very differently and some at higher voltages. but for the WS2812B, it’s 5V and 5V only. \$\endgroup\$ Commented Sep 16, 2018 at 16:47
  • \$\begingroup\$ @stancejontland The power DOES NOT need to go through the Magic Controller for the LED strip. The only thing that is important coming from the controller is the serial data. I seriously doubt that the controller has the capability of handling 15+ amps. \$\endgroup\$ Commented Sep 16, 2018 at 18:45

The WS2812B datasheet tells you:

  1. Each pixel is 3 * 16mA = 48mA max per pixel. A 15A 5V power supply is required at minimum to power your whole strip at maximum white.
  2. The VCC voltage per pixel is a nominal 5V (the controller in the chip generates a 12V CC to drive each LED). The pixel will work perfectly from 4-5V and so you can support a voltage drop over the strip of 1V. If you have an adjustable power supply, then you could increase the input voltage to 5.2V to handle even more voltage drop along the strip.

The Magic controller does NOT modify the input voltage for its output VCC. While the Magic controller will run on voltages from 5-24V YOU CANNOT feed this through to your LED strip. The maximum EVER for your strip is 5.3V and 5.2 as maximum is advisable.

The Magic controller instructions say the following:


Model: SP105E Bluetooth Magic Color Controller Working voltage: DC5V~24V ( Please choose the correct power supply according to you led lights. If your light's working voltage is 5V, please use a 5V power supply, not 12V/24V power supply. ) Remote distance: 20 Meters Product size: 85mm*45mm*22mm


It can support WS2812B, but there is no WS2812B option on the setting page. Please choose WS2811 when connect it to WS2812B. The controller cannot regulate the output voltage at the VCC. That means the output voltage of your power supply must be the same as the work voltage of your led lights.

There are endless power supplies that might suit your functionality. For example Autove (who sell the Magic controller) offer this power supply on Amazon for exactly your purpose.

If you are going to use your strip at maximum white for long period of time, I'd suggest that you might want to use a 20A+ supply. Autove offer an example on amazon with this supply which has screw terminals providing a much better connection and current capability.

If you are concerned about the voltage drop along your LED strip you can run a pair of wires (VCC and GND) to each end of your strip to minimize the drop. The barrel connector on the Magic controller is inappropriate for 15A+ so you should be powering the LED strip separately as shown below:

enter image description here

Taken from this document.

  • \$\begingroup\$ i was looking at the power supplies you put in the links and i do not know how i would power that power supply. \$\endgroup\$ Commented Sep 16, 2018 at 19:02
  • \$\begingroup\$ using your picture here my strip ony has 3 connection points on the struip. it says +5v din gnd and every other section the din changes to DO \$\endgroup\$ Commented Sep 16, 2018 at 19:08
  • \$\begingroup\$ @stancejontland Correct, there is only one data line for the CLK/Data using an NRZ protocol. The image I clipped was generic, and the controller is used for multiple chip types. The power supply is 120/240 AC driven and you'd have to make a mains cable. If you can't work this out then perhaps it's simply too challenging for you. ….or supply use the first power supply which has an IEC connector and mains cable. You could cut your LED string into two sections and use two of the 15A power supplies to reduce the overcurrent in the barrel connectors. \$\endgroup\$ Commented Sep 16, 2018 at 20:16

AS pointed out your need 15A@5V or 75W which you can get on most PC ATX PSU's.

https://randomnerdtutorials.com/learn-esp32-with-arduino-ide/ will help with interfacing and other options. Voltage drop on the cable may be minimized by use of heavy gauge wire. Interference may be reduced using the earth grounded PC supply.

  • 1
    \$\begingroup\$ This seems needlessly complex for a new user, and the form factor is horrible. Asking a newbie to convert an ATX power supply to the task seems over the top. \$\endgroup\$ Commented Sep 16, 2018 at 15:58
  • \$\begingroup\$ Perhaps YOU misunderstand. Interfacing with 2 or 3 Molex plugs with 5V 10A per plug is trivial and almost free with a surplus >350W supply. to get 5V @15A= 75W It might be possible to share it from an existing tower. \$\endgroup\$ Commented Sep 16, 2018 at 17:37
  • 1
    \$\begingroup\$ Right! And this for an OP who didn't understand that the 400mA 4.5V power supply was inadequate. \$\endgroup\$ Commented Sep 16, 2018 at 18:41
  • \$\begingroup\$ i pulled my old pc power unit out and now im stuck trying to figure out how to get the power to the controller. \$\endgroup\$ Commented Sep 17, 2018 at 2:37
  • \$\begingroup\$ how do you insert pictures? \$\endgroup\$ Commented Sep 17, 2018 at 2:40

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