Power Requirements

Recently I received 4 5M RGB LED(SKU: CE04853 ) strips that I am planning to turn into a scrolling message matrix. What I would like to is the power requirement for the 4 strips linked together. How many do I need to provide?

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Hi Adrian,

Adafruit’s NeoPixel Uberguide is overall fantastic, but it also has a specific section on estimating power requirements for WS2812 LED strips which I’ve linked below.

Ultimately you will need to make some estimates based on if all LEDs in the strips will be on full brightness white setting, or if they are usually only partially on at any given time.

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The 5m strip is 30 Leds/Metre total would be 4530=600 LEDS.

Hi Adrian
As a point of interest where did the 4530 come from???
30 LEDs / metre = 150LEDs / strip so 4 strips @ 150 LEDs = 600 LEDs. Just that the 4530 has me a bit baffled.
Cheers Bob

Hi Adrian
I have not gone into fine detail as personally I like to over cook power supplies a bit, ; leave some head room.
But here is an approximate run down.
Each LED is actually 3 LEDs so if we assume max current at White using 20mA which is 60mA (0.06A) total then with all LEDs on that equates to 36A. BUT that is very very bright so in practise you may want to operate at half current which would be 18A. This is with all LEDs on.
You may only have half the LEDs on at any one time so this would reduce to 9A. Getting better.
The above is for White LEDs which you have to consider as being worst case. Other colours reduce the current accordingly for instance if displaying Red only one internal LED is on so the current is only one third but you have to consider worst case (White).

It is up to you what scenario you intend but even if half the LEDs at half brightness I would not go below 10A. With 4 strings that would be my minimum. If all the LEDs are on all the time increase that to 20A. With situations like this the power supply can rarely be too big as bits will be added later.
Cheers Bob

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Hi Bob,
That was meant to read 4x5x30=600. It looks the asterix was removed from the message. Let me see if I have correctly understood you :-
Each LED is 20mA or .02A, each pixel = 3 LEDS(R,G,B) = 60mA
600 pixels x 60mA = 36A
To drive the entire 600 pixels i would need a 40A power supply as least to be safe. With that would I need to inject additional power along the 600 pixels? Of that is for full brightness white correct? I tried half brightness white it didn’t look to bad.
For testing at present I am using a 5V 3A power supply. Either I will kill the power supply or not drive the pixels to full strength correct?


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Hi Adrian
What you have said is essentially correct for my assumption of LED current requirements. But read on as Core have quoted a lower figure which modifies the actual numbers a bit.

If you are using a switch mode supply you will stop or kill it. If the power supply is any good this will only be temporary. Turn the LEDs down to about half for testing purposes and you should be OK to drive 1 strip but not enough to drive all.

Core quote 1.1A per metre for full brightness which is a bit less than I guessed . That is a total of 22A. I would use 25A at a minimum but anything over would not hurt. At 5V that is 125W and I think 150W (30A) is a common unit.

I am assuming from the bit of info you supplied that these 4 strings are in series. That is you effectively have a long string of 600 LEDs.

Data and Ground have to be connected from the start to finish. I think the Data connection is marked with little arrows to indicate direction which should be self explanatory.

Power. The 4 strings will be too long to connect at one end only as you might have a voltage drop problem. I think these LEDs are pretty forgiving but you might as well prevent any problems in the first place
There are a couple of ways to do this.

  1. Run 2 fairly heavy wires from the power supply, one connects to the 5V point at the junction of string 1 and 2 with the LED 5V wires connected together. repeat with the other wire from the power supply to the junction of strings 3 and 4. The 5V wires at the ends remain free, make safe to prevent shorts. The 5V wires at the junction of strings 2 and 3 can be connected, this will make no difference.

  2. Run 5 smaller wires from the power supply to the 5V connection at the ends and all 3 junctions.

Both methods have their pros and cons. The actual wire size will depend on how far it is between power supply and LEDs. The greater the distance the larger the wire that should be used. As long as you are careful this should see you out of trouble.

A reminder, that 3A supply will only be good for 1 string at about half brightness.
Cheers Bob
Where I say half brightness I maybe should say half current which is not necessarily half brightness as LEDs may not be terribly linear.

Important Edit:
I have been a bit slack. Referring to the above power connections. Just in case it is not obvious there are more wires of the same size to run from the negative side of the power supply to the negative or ground connections at the same points as the positive wires. This does not change the requirement to connect the ground (or negative) and Data circuits right through from one end to the other in the correct direction.

It is also important to connect the ground along with the Data to the Arduino or whichever device you are driving the LEDs with to the device ground.

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