LED lighting for Burning Man art project

Discussion in 'General Electronics Chat' started by Zed the Mailman, Jul 1, 2011.

  1. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    Hi all-

    I'm turning to you for help. Our original plan of using ELwire isn't going to work so we're looking to make our own LED 'rope' type lighting.

    It's going to be a collection of (3) 150' long boardwalks to ride bikes on. They are going to be arranged in a loop with a small structure to house the batteries at a point in the loop. Take a look at the construction here:
    <img src="http://i.imgur.com/60yoW.jpg" alt="" title="Hosted by imgur.com" />

    I'd like to use a couple deep cycle 12v diesel truck batteries and maybe a 24hour timer, hopefully they won't have to be charged every day.

    can you guys help me figure out what I need and how I need to configure it? I'm not much of an electrical wiz and have almost no experience with LED's.

    If I light each course with a small, narrow focus LED every 10', that means i need to create a "bank" of 15 LED for each course.

    I need to do this as inexpensively as possible, any help is very much appreciated.
     
  2. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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  3. nickelflipper

    Active Member

    Jun 2, 2010
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    Have you thought of the 5050 led waterproof modules or a reel of 150 on flex pcb? They are set up for 12V power, and include the required resistors. The beauty of the 3 led modules is the power and ground are already wired and soldered. The flex pcb reels will be cheaper, but will require cutting, wiring, soldering.
     
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
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  5. nickelflipper

    Active Member

    Jun 2, 2010
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    Wow, those extrusions and lens caps are really something. They keep coming up with new types of reels all the time too.

    The individual modules I was talking about are made for backlighting in the signage industry, like these http://cgi.ebay.com/20PCS-3-LEDs-Li...159?pt=LH_DefaultDomain_0&hash=item4aac67cab7
     
  6. KJ6EAD

    Senior Member

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  7. SgtWookie

    Expert

    Jul 17, 2007
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    I think the boardwalk construction idea is problematic; you don't indicate how wide the boardwalk will be, but if it's over 16" wide you will need to add another stringer in the middle; one every 16" - otherwise, you will wind up with collapsing boards and possibly injuries.

    You will also need cross-braces so that the stringers can't rotate and collapse.

    Intermixing 2" thick boards with 1" thick boards isn't a good idea; it's trip hazard if someone is walking.

    Putting lighting in the middle of the decking is problematic for more than one reason;
    1) You'd have to drill/notch/etc the board, which will create a weak spot in an unsupported area.
    2) If located in the center, dirt will collect at the highest rate, causing the LEDs to appear dim after a short period of time.
    3) Easy to damage the LEDs that are situated in the traffic pattern.

    Rather than illuminating in a "center strip", consider illuminating from the sides. You could have a small raised curb, and use wide-angle LEDs to provide diffused lighting.
     
  8. KJ6EAD

    Senior Member

    Apr 30, 2011
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    When one thinks of "Burning Man" and "Art Project", practicality and the laws of physics are generally a peripheral concern. ;)
     
  9. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    Thanks for your interest!

    The reels of LED's are way out of the budget. Super trick and looks like it would make our life easy, but way out of the budget.

    The boardwalk design is set in stone. I'm completely comfortable with it. The courses are one directional and the 2x4's will have a bevel on the leading edge to make it smoother. Overturning isn't a problem with the 4x4 stretcher every 8' and the span is only over 16" is one place that has a mid-span stringer.

    Locating the LED's in the center of the travel path is a good point, I think I'll relocate them about 6" to one side.

    what I'm really looking for is advice on how best to design the system. I've been reading up a bit. My idea is to create 3 separate "rope" like strands with a LED or 2 every 10 feet. We'll lay this rope light down into the cavity between the 2 stringers and when we get to the 2x4 board we'll route the wiring up the kerf and into the small housing. A dab of silicone or hot glue maybe to secure it pointing in the direction and a small plate of aluminum over the top to protect it from tires.

    From my limited research, it looks like I should wire these things in series and 'balance' them such that each rope draws about the same.

    I'd really like to pre-make (3) 150' long 'ropes' with LED's every 10' to bring out, ready to wire up to power. Do you see any problems with this?

    We'd like to use (2) deep cycle 12v batteries to run it. Also a 12v, 24hr timer so it can come on automatically at 8:30pm and turn off at 5:30am

    I appreciate any tips you've got to help me figure this out.

    Thanks,
    Zed the Mailman.
     
  10. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    So I ran down to radio Shack and picked up a couple 2-packs of LED's for a test.
    http://imgur.com/a/LcaCt

    I'm going to make a simple (3)LED 'rope' as a test, since it's just a test I won't space them 10' apart, just a foot or so. I think my schematic should look like this:
    http://imgur.com/tScCq

    If R=(Vs-Vl)/I and
    Vl = 3.3 + 3.3 + 3.3 + 2 (3LED@3.3v + approx 2 for the resistor)
    Vl = 11.9

    So R = 12-11.9/I ---->0.1/0.025 = 4

    Am I doing this right so far?
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Not completely.
    You state the power supply is 12 Volts.
    You state the leds are 3.3 Volts each, you use 3 pieces.
    So the voltage accross the resistor is (Vsupply - 3 X Vled)= 12 - 3 X 3.3 = 12 - 9.9 = 2.1 Volts.
    You want a led current of 25 mA (0.025 A) so the resistor is Vresistor / Iled = 2.1 / 0.025 = 84 Ohms.
    As this value is not a standard value we choose the next larger value wich is 91 Ohms.
    The current will be 2.1 / 91 = 0.023 A = 23 mA.

    Bertus
     
  12. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    Thanks Bertus. I was a little confused about if i should include an estimated value for the resistor in the Vload.

    I'm going to go grab a 91Ohm resistor and give it a try.

    The next step will be to design the schematic for a full 150' run. This will have 15 LED's in it. If I use the same 3.3V ones, I'll end up with a Vload of 49.5V. Is there any way I can run this off a 12v deep cycle truck battery?
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    If you want to make a string of 15 leds, I would break them up into 5 strings of 3 leds as calculated before.
    These 5 strings can be put parallel on the battery.

    BTW what is the actual voltage of the battery.
    A voltage of 12.8 Volts (wich is quite normal for lead batteries) will already give a ledcurrent of (12.8 - 9.9) / 91 = 0.042 A = 42 mA, wich may be to much for the used leds.

    Bertus
     
  14. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    Bertus- How about (2) 12v deep cycle truck batteries in series to get 24v? Then I could do each course with (2) 7-LED ropes? Or perhaps I could use lower wattage LED's to get more of them on 1 rope. I'm not set on these 7000mcd illumination LED's from Radio Shack. That's just what they had and I figured would work fine for testing purposes.

    It looks like these may be more appropriate for my project
    http://www.ledsupply.com/l1-1-w5th15-1.php
    Bright with a very narrow field. Since I'm illuminating a straight walkway and these look to be quite bright, maybe I could get away with spacing them every 15' instead of every 10', eliminating 10 LED's.

    At 3.2v each times 10 LED's that's Vload=32. If I put (3) 12v batteries in series I could get +36v, enough to drive an entire strand of 10 LED's. Does this seem like a reasonable approach?
     
  15. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    SUCCESS!
    http://i.imgur.com/uP6rA.jpg

    This is just a test, for my real application there would be 10-15 feet in between each LED but I'm happy that it worked.

    Since the battery tested at about 17v I use (3) 100ohm resistors.
     
  16. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    On the heels of my successful test, I've revised my schematic for a single "rope" of light.
    http://i.imgur.com/564Qa.jpg

    Any advice is appreciated.
     
  17. nickelflipper

    Active Member

    Jun 2, 2010
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    Here is a source for some narrow angle leds that could save a bundle, resistors too http://www.dipmicro.com/store/index.php?act=viewCat&catId=511. At those prices, you could afford to space them every 5 ft. I have some of their blue ones, and it just plain hurts to look at them straight on.

    The 100 ohm resistors should be a good compromise. Running these leds at 15-20ma won't visually be much different than running them at 25ma.

    EDIT: you only need one battery, like the first schematic and run them like rungs on a step ladder.

    Code ( (Unknown Language)):
    1. |____________|
    2. |            |
    3. |____________|
    4. |            |
    5. |____________|
    6.  
    7. Gnd,led,led,led,Resistor,Pos12V
     
    Last edited: Jul 5, 2011
  18. SgtWookie

    Expert

    Jul 17, 2007
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    In your schematics, you have shown the LEDs connected backwards. To get current to flow thru the LEDs, you need the anode connected to +, the cathode towards negative.
     
  19. Zed the Mailman

    Thread Starter New Member

    Jul 1, 2011
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    Thanks all. Any ideas on how to create a 10 or so LED rope? I understand that I can use 3 at a time but the 'runs' back to the batteries using this method will be hundreds and hundreds of feet. If possible I'd really like to have (3) 150' ropes of 10-15 LED's.
     
  20. nickelflipper

    Active Member

    Jun 2, 2010
    280
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    When comparing the 3 series led, or 10 series led, there is no more positive supply wire, or negative supply wire. They both will be 150 ft. each: Think of it as a common supply rails, tap into it wherever you want.

    Looking at my poor attempt at ascii drawing, I left out the connecting "|" because the editor wouldn't let me insert more than one blank space. Should have put code tags around it and tried to preserve the spacing. I'll make a stab at editing.

    The assumption is that the battery would be in the middle of the span to negate voltage drop, this needs to be calculated to correctly size the gauge of wire.

    One or two fuses (middle battery scenario) should be incorporated on the positive leads from the battery, to guard against shorting across the supply rails.
     
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