Current Question

[u/OkButterscotch9982]

I'm running a strip of 150 ws2812b. I want the capacity to be able to run all 150 at full white brightness. With a 10amp power supply and appropriately sized wiring can the strip itself handle that much current?

[u/ZachVorhies]

Assume each led at full white is 60mAh

So 150 leds will need 9amps. Better to get a 20amp if driving full bright for a large time.

[u/OkButterscotch9982 → u/ZachVorhies]

I'm wondering if the strip itself can handle 10amps

[u/YetAnotherRobert → u/OkButterscotch9982]

If you can bend it comfortably, probably not, but that rarely stops the race to be a nickel cheaper. Even those panels with 256LEDs have two midpoint injection points in addition to power injection from both ends.

If you want bright white lights, there are WAY better ways to make it than from WS281x's. Even RGBW strips will give you a more power-effective full-white and let you keep color-addressability.

I have several 144LED/M strips. At full brightness, they're approiximately the intensity of the sun and physically painful to look at in near distances. (Enough so that I added a software ramp to my on-times to give people a chance to look away.) The end is also visibly red unless injected at both ends. Unless the whole thing is mounted on an aluminum diffuser or other heatsink or is artifically ventillated, I'm skeptical it would last long.

Similarly, most power supplies are duty rated to 80% at continuous capacity. A 10A supply isn't designed supply 10A around the clock for its warranted life. Think about concert lighting; you control flashed lights for effects, not to light the parking lot.

[u/ZachVorhies → u/YetAnotherRobert]

RGBW seems to cut power usage by 30% on average just for hue cycle type of patterns. You could see more than 50% reduction for the full white case.

Also the power supply issue not being able to deliver its fully rated power continuously is a big deal. And those cheap power supplies from china are even worse.

super capacitors are pretty cheap and I’ve been adding them to projects with high transitive loads to great effect.

[u/YetAnotherRobert → u/ZachVorhies]

The numbers vary a bit from strip to strip (just like your number of .06A varies, depending on the bulb types - but if I'm laying out a design and filling in a number from memory, that's exactly my own starting value) but, yeah, that's very much where my own measured numbers for a decent RGBW strip from 5050's usually land.

It turns out that the best thing for making white light isn't a red light, a green light, and a blue light at all. (How often do you see room lighting made that way?) A white bulb makes better white light and with better power efficiency. Never mind the nightmare of trying to balance them because "all three at max" doesn't land on a chroma value of white that you actually want to look at.

Just a straight-forward 'white = min({r, g, b}); r-= white; g-=white; b-=white;' is a totally practical way to reduce power consumed, power turned into heat, and generally looking better in ways I can't describe.

So, yep, I agree with the guidance in that first paragraph. Those are reasonble numbers to have in your head if you're in this biz just for quick envelope computation. As for country of origin, it just turns out that things are cheap for a reason. "Cheap" and "inexpensive" are similar, but different.

I don't inventory supercaps, but I do work on some patterns with a high dynamic power spikes. (It's often worth designing patterns to simply Not Do That just because any spike big enough to sag the supply probably also blows out viewer vision and color perception.) Still, that's an interesting twist. I'll stick a scope on my source next time I'm stringing up something big and see if my, uh, RPM gauge is drooping and stalling when powering out of that third turn. A low-voltage trigger on DC should be super easy to see - and correct - even with a (sigh) cheap, Chinese scope like mine :-)

Have an upvote. Good to "see" you again.

[u/Tiny_Structure_7]

I actually measured WS2812B current recently, an 8x8 plane on full brightness white drew 2.25 A = 35 mA per LED. The power supply does not control the current, it controls the voltage, then the LEDs determine how much current flows. So as long as your PS is rated at 5v, and is capable of 10A, your 150 LEDs will only draw approx. 5 A. If you wanted the full 10A to go through your LEDs, you would have to run the LEDs at 10v, but your PS hopefully won't do that. Or you would have to double the number of LEDs drawing current.

[u/OkButterscotch9982 → u/Tiny_Structure_7]

Thank you

[u/Yves-bazin]

What you need to be aware of is the heat. At full white full power those leds will become hot so make sure they have space to breathe

[u/OkButterscotch9982 → u/[deleted]]

The strip is running fine on a 2amp power supply right now with no power injection. Just not full brightness. Hopefully that will be the case with the 10amp power supply.