# WS2812b LED strip power supply [duplicate]

I am currently trying to light up a staircase at my house. I bought two 5M reels of WS2812b 5V LED strips on AliExpress and some solderless connectors... I am planning on putting about 40cm on each step, which would in total be exactly 6 meters of LEDs. One thing I am struggling with is choosing a correct power supply for my needs. The seller says that the strip needs 18 watts per meter.. Which would make 18*6=108W in total. Do I need a power supply that has exactly 108w or can it be more (or less)?? Also I am connecting each step in parallel with the next one. Does this change anything? And If I choose a power supply and then use the LEDs on half power (or less), does that matter? Thanks in advance!

PS. My wiring will be the same as on this image: https://cdn.instructables.com/FOD/XLFY/IGTY8XVX/FODXLFYIGTY8XVX.MEDIUM.jpg

## marked as duplicate by Wesley Lee, PlasmaHH, Olin Lathrop power-supply StackExchange.ready(function() { if (StackExchange.options.isMobile) return; $('.dupe-hammer-message-hover:not(.hover-bound)').each(function() { var$hover = $(this).addClass('hover-bound'),$msg = $hover.siblings('.dupe-hammer-message');$hover.hover( function() { $hover.showInfoMessage('', { messageElement:$msg.clone().show(), transient: false, position: { my: 'bottom left', at: 'top center', offsetTop: -7 }, dismissable: false, relativeToBody: true }); }, function() { StackExchange.helpers.removeMessages(); } ); }); }); Mar 17 '17 at 10:47

Also I am connecting each step in parallel with the next one.

That's the correct way to power them. The data should be in series (I'm assuming you realize that these LEDs need a processor or some sort of controller to drive them, you can't just supply power and expect to see anything).

Power requirements depend on what color you want. The power rating is for full brightness white, anything else will use less power. Any fancy patterns, e.g. ripples going down the stairs, will end up using a lot less power since for most patterns roughly half the LEDs will be off at any given time and the ones that are on won't all be full power white.

If you are getting close to full power then you'll need to connect the power in at multiple points. Running a 5 m 300 led strip at full brightness and feeding 5V from only one end the last LED was getting about 1.9V. I ended up supplying 6V at both ends and the very middle was just starting to look very slightly yellow due to the voltage drops. Anything longer and I would have needed to also supply power to the middle of the strip.

• Data can be parallel as long as the inputs/cabling in parallel does not cause a problem to the driving device. In this case all LED strips have the same color sequence. – Wesley Lee Mar 17 '17 at 11:06
• True. It just seems a massive waste flexibility if you were to do that. Especially since stairs are essentially serial in nature so it doesn't give a significant simplification in design. – Andrew Mar 17 '17 at 11:12
• Well, considering that if a single LED dies the whole string dies, and that longer strings lead to lower frame rates and more memory required, I'd say there are plenty of uses for parallel data on the strips. :P – Wesley Lee Mar 17 '17 at 11:13
• Assuming 144 LED/m strips I make the maximum refresh rate for 6 m in series to be around 750 Hz. I doubt frame rate will be an issue. The frame buffer would be 2.6 kbytes, not tiny but not exactly massive. For lower density strips the rate goes up and buffer size goes down. The whole loss of the chain on failure issue is why the 2813 exists but he has 4 m spare so making a few spare steps worth to swap out is probably easier. I'd say you have good points for larger systems but not for a system this size. But we are well within opinion territory at this point so each to their own. – Andrew Mar 17 '17 at 12:06
• No. The WS2812 is a serial device. End of story. No parallel data connections. Anything else is a kludge. – Misunderstood Mar 19 '17 at 2:12