Can I get away with no power injection, if running 5V strip at 50%?

[trevor_]

Hi all,

I'm still very new to this, and I'm thinking of adding a 10m long straight run on my front porch.

I'm thinking of going with two 5m strips of 5V WS2812 or WS2811 at 30 pixels/m.

http://spikerlights.com/calcpower.aspx is showing me green if I run the lights at 50% (attached).
Is this right? Can I get away without power injecting if I run the lights at lower brightness?

Thanks in advance

 

[djgra79]

On paper, yes. In practice, probably.
Everyone's mileage will vary due to external factors such as cable/wire used (both guage and length from prop to PSU/controller), colours used, connections used (strong solder joins etc)
I go by the trial and error method which doesn't suit everyone. But if you try all white and the colours look off especially towards the end of the length then they need more power.
A question for you however, why is it you are trying to get anyway without power injection?

 

[Skymaster]

10m at 30px / metre is 300 pixels, not 150 as you have in the calculator there.
Additionally, strip has got some pretty rubbish gauge tracks on it, which would bump up resistance a fair bit.

So I'd say no.

 

[Skymaster]

Further to the above, you'd want to inject in the middle, where both strips join, and probably at the far end. That would give you a much more successful result.

 

[trevor_]

Thanks both! Looks like I'll have to give it a bit of a trial and error. I'll likely have to inject twice then...
The only reason I'd like to avoid injection is because there's not much space for much cabling (without it looking messy), since I want the strip flush against the wall, though I could make some holes in the brickwork to run the cables through from the subfloor space...

 

[KiwiPhil]

if its 5m strip, don't forget you could also just run both from the middle and have them running outwards in different directions, this may be simpler or more complex depending on your needs