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RGB pixel strip - bending radius, power limits?

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by zeph, Jan 7, 2012.

  1. zeph

    zeph New Elf

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    Bending
    What's a reasonable minimum radius for bending a silicon tube pixel strip (such as sold by Ray Wu and others) - along the less flexible axis? For example, could I bend a 5m stip into a 0.8m radius (1.6m diam) circle? Probably not, but from those of you who have worked with these strips - how small can one make a circle? 1.6m (ie: two 5 m strips for the circle?

    (I gather one could cut it periodically and splice segments with 4 wires, but that would interrupt the smooth curve as well as causing waterproofing issues, right?)

    Power
    The second question is about power. I would think that at 5v, a 5m 150pixel strip @ 60ma/RGB pixel would be over 9 amps full on (including chips), right? Wouldn't that be too much current/heat for the flexible PCB at the feed end, and also have too high a voltage drop at the far end? How long a strip can one really power from one end? Are there tricks?

    On the other hand, there are 12v strips. It would naively seem in that case that each controllable "pixel" would need to be implemented as multiple RGB led's, like three in a row that change together, right?

    I would like to create a full circle of individually controlled RGB pixels. Smaller is somewhat better. Is that even feasible with pixels strips, or must one use pixel strings and individually place each LED?

    Thanks for some pointers, as I migrate towards pixel displays...
     
  2. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    you can still get a decent bend in the strip by mounting it and allowing the strip to slightly kink between each cable tie. I was able to get a decent radius in my arch way seen in this video

    Fasteddys 2011 Colour Christmas Light Show

    I would use the silicone tube coating for this as it allows for tighter bends.
    I cant answer you on the 5vdc strip as prefer to use 12vdc strip. but having a resolution of every LED having an IC so it is 96 channels per metre is an overkill especially for outlines, would work well for a matrix though. Remember the more channels used the more horsepower you need to run it and more is not necesarily better because when viewed from the street a 100mm section of strip isnt a very large section at all.

    The strip i am now planning on using for 2012 is this due to the cost and being 12vdc. You are correct in your assumption that for 12vdc you are controlling 3 LEDs instead of the one with the 5vdc strip.
    What you plan to do has been done using LOR CCRs 5metre strips which are 10 pixel 30 LEDs per metre and 12vdc which can be seen here

    Deck the Halls - Christmas Light Show - 4 Circles - Presented by SuperStar Lights - Allen, TX

    If you plan to go a very tight radius then you may be better off either using the pixels strings or the pixel modules as these will allow for a much tighter radius.
     
  3. OP
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    zeph

    zeph New Elf

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    Thanks - exactly what I needed to know! I should get over my idea of controlling of every LED, in which case 12v and groups of three make more sense - and from the videos, much smoother than I had realized.

    I hope I can ask some more questions.

    How did you mount the apparently very smooth archway? (eg: on bent pipe, plywood, etc)

    What did you use for the candy canes? Pixel strings?

    Does the IP65 rating of the strip you plan to use concern you (how much does IP rating matter?)

    Wow, the video by SuperStar lights is awesome - much along the lines of what I wanted to do but way ahead of me. But I gotta start somewhere.

    Thanks!
     
  4. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    I used 25mm electrical conduit with the strip just cable tied to it, very easy and quick to build

    The candy canes used modules and further info on their construction can be found here
    http://auschristmaslighting.com/forums/index.php/topic,1723.0.html

    One of the main reasons i prefer to use strip and modules over pixels is due to the great water resistance compared to the strings which can suffer from water ingress issues. There ares some newer strings that have appeared to overcome this issue.
    The IP ratings from Chinese vendors are not usually as accurate as one may think so I always look at the actual construction rather than the rating and this is why I'm a fan of using the solid silicone strip and modules as these have a construction that prevents water ingress issues. The newer strings are made of a solid resin moulding and so the construction allows for a much higher degree of protection.
     
  5. David_AVD

    David_AVD Bite my shiny metal ass!

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    If by "less flexible axis" you mean bending the strip sideways, I don't think you can bend it much at all without massive damage.
     
  6. OP
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    zeph

    zeph New Elf

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    Uhoh, now I think I'm hearing conflicting information. As a newbie, that is like a parity check error and so I'm checking a bit further just in case.

    I understood FastEddy to be saying that it can be bent; it looks to me like his front archway is 5-6 feet across, and I think the circles in the Brian Bruderer video are about 5 feet diameter (to fit one 5m strip around). What I understood from FastEddy is that the strips crinkle a bit at the places where you put the wire ties (ie:the cut-here locations between the chip & LED wiring sections) but that's OK if you aren't flexing it repeatedly. So that's what I was going to go with. Do I understand that?

    Both FastEddy's archway and Brian's circles may have been made from LOR CCR's rather than Ray Wang's strips, tho. Are they structurally different in this regard?

    I'm still a little uncertain about the relative value of Silicone Coating vs Silicone Tubing. For example, see the pulldown at:

    http://www.aliexpress.com/fm-store/701799/209843764-519162566/5m-led-digital-strip-DC12V-input-WS2801IC-256-scale-12pcs-IC-and-36pcs-5050-SMD-RGB.html
     
  7. David_AVD

    David_AVD Bite my shiny metal ass!

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    The LED strip comes on a roll. Obviously you can bend it that way. What you can't do is bend it sideways.
     
  8. Bird

    Bird Proud LOR user

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    That's not totally true. I bent mine sideways.

    Granted mine were on arches so the radius was not that tight (see web site link below), but I could have made the radius smaller.

    These were LOR CCR's.

    In any case, you need to handle all RGB strips with great care. I did and had no issues at all.

    Bending it 'sideways' did kink the strip slightly. I did not make the cable ties tight, but left them just snug enough not to allow movement in the wind.
     
  9. OP
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    zeph

    zeph New Elf

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    As a partial answer to my question, by following the hints (er, checking the URL in the second video) from FastEddy, I found this page:

    http://www.superstarlights.com/Other/CircleConstruction.htm

    Notice the bottom photo - it appears that he is bending the strip "the stiff way" into a circle of about 5' diameter (196" circumference). There's some buckling at the cut points.

    Bending in the roll direction of course, there's no question - it's supposed to wrap around a 3" pole. But I wanted a circle facing the audience, which does appear feasible, at least for a 5' diameter.

    ===

    Also, for the LOR Cosmic Color Ribbon (which appears to be similar to Ray Wu's strips), the spec says "Can conform to a 3” diameter bend along its long dimension and a 3’ diameter bend in the plane of the ribbon"

    http://www.lightorama.com/PDF/CR150D.pdf

    The CCR may however be a more premium variant of the Ray Wu pixel strips (as well as including a controller and power supply) - does anybody know?
     
  10. David_AVD

    David_AVD Bite my shiny metal ass!

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    I take it all back - you can bend some of those strips sideways apparently. :)

    Would I do it? No. :D
     
  11. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    The solid silicone strip disperses the light better and is much stronger than the silicone tube. But for your application you want to be able to ripple the strip with the bend radius so it will face outwards and the silicone tube allows for a better bend in this respect. You can still use solid silicone but i doubt you would achieve a tight a radius as if using the silicone tube.
    The pictures below show how its done.
     

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  12. DeeJai

    DeeJai Is that Magic Smoke?!?

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    This is definately increasing my interest for strip arches this year.
     

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