Getting my head in a spin with LED power...

Other Hardware LEDs and Multiplexing
1

Hi,

Ive managed to learn alot in the past few months...but unfortunately i cannot seem to grasp what would seem like the most fundamental and simple thing - power.

To quickly explain what Im wanting to do - im after running 250 5v LEDS (WS2812 strips - ~250 x 60ma) but am trying to avoid using an external 75w 5v psu because i dont want to concern myself with housing the device into an external box as its too large to sit with my project, and tbh it scares me a little bit!
As a result id prefer to use a standard external desktop brick that i can simply just plugin and away i go, however 5v power adapters only seem to be available at upto 10amps which is not enough juice should all my LEDs be left on pure white. Im sticking with 5v as i want to use the ws2812 as theyre cheaper with the IC built into the actual LED.

Now this is where it all falls apart for me...

A 5v 10a power adapter delivers 50Watts which is not enough.
A 12v adapter at 7a that then delivers 84watts.
The LEDS use 7.5 watts per 30 / 5v@1.5a.

Is there a way to use the 12v power adapter and use its 84watts to run these LEDs safely? Ive seen loads of DCDC buck converters that have an output of 5v 8a (40 watts). Could i connect 2 of these buck converters to 2 sets of 125 LEDs seperately and connect both to the 12v supply and all be fine? The watts add up to within the range of the power adapter but im not really sure if ive got totally the wrong end of the stick.

Any help, advice, lectures would be most welcome. Id feel safer running off a 9v battery :slight_smile:

cheers all,
Carl.

2

Why not use a couple of the smaller 5V supplies? Power the LEDs in multiple groups, and connect all the grounds together.

3

Yeh i could do that, would just be a little neater with 1 power block thats all and probably about the same price once shipping comes into play.

thanks

4

I don't see how you get away from something like this
http://www.mpja.com/5-Volt-Power-Supply-20A-100W-Switching-Hengfu/productinfo/16011%20PS/
for the total 15A of current you are interested in.

5

Your LED strips probably aren't designed to carry 15A of power at a single input. You should add additional wiring and inject the power at multiple points along the strip.

15A would be a solid 14ga cable or .25" wide trace on 1oz copper.