Positioning LED's inside a plastic tube

Discussion in 'The Projects Forum' started by RyanKH, Dec 26, 2010.

  1. RyanKH

    Thread Starter New Member

    Dec 26, 2010
    Thanks in advance. I would like to mount a series of LED lights inside of clear tube - probably a vinyl tube. The tube will be long - likely 80 feet. Despite the length, it's only a handful of LED's.

    What's a good way to get the LED's positioned and fixed in the right spots? Should I build the entire circuit, pull it through the tube, and just affix it in place at the ends? Do they need to be affixed at different points, or each LED glued to the inside of the tube?

    Here's my original project thread: http://forum.allaboutcircuits.com/showthread.php?t=47544


  2. someonesdad

    Senior Member

    Jul 7, 2009
    You don't give any drawings, schematics, or dimensions, so it's hard for people to understand exactly what you're doing. Just make a pencil sketch on a piece of paper and take a photo of it -- no need to use any fancy computer drawing tools.

    You also don't say what type of vinyl tubing you're using. If it's something like the typical cheap stuff at the hardware store, it may be a challenge to get something pulled through it. But there are ways. One concept is to attach the string of LEDs to something like a rubber stopper that will seal reasonably well with the inside of the tubing, then use low pressure air (perhaps in the 1 to 10 psig range) to push the stopper through the tube, which would pull the LED string along with it. Or, use this to pull a piece of string through the tube, then use the string to pull the LEDs. You're going to want to make sure that the electrical joints are solid and will withstand the assembly techniques. The trick will be to make sure that the stuff entering the tube doesn't catch on the edge (it would help if you have some experience pulling wire through conduit).

    I'd also worry about the corrosion of the electrical connections. Personally, I'd want everything to be watertight and not allow any pool water access to the connections; otherwise, corrosion is likely. An easy way to do this with vinyl tubing is to make a suitable plug for the ends (this will be equivalent to a vacuum feedthrough because it will contain your wires, but yet be watertight); this plug should be a reasonably tight slip fit into the tubing. Then use a little waterproof silicone grease on it and secure the tubing to it with two constrictor hitches. I use this method to hold brass fittings on our water hoses around the yard and some of our hoses have 20 years of use on them. The trick to making a tight knot is to put a bowline in each end, then use two sticks to pull the constrictor tight. Works like a champ. Look it up in the Ashley book of knots if you want to see a picture.
  3. Wendy


    Mar 24, 2008
    I agree pretty much with what has been said, with one minor addition. If you use stiff solid gauge wire it may help keep an LED in a fixed position. Still needs to be insulated though, they make a product named "liquid electrical tape". You paint it on, it dries, and you have the places you soldered insulated.
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    Some LEDs have a very, very narrow beam (especially super-high brightness ones from eBay), so if looking at one from the correct angle, it is nearly blinding.

    A workaround for this is to cut off the rounded tip of the LED to remove focus, then one needs to see the area the LED is in, and can readily see if it is on or off without blinding themselves. Another trick is to simply blob hot glue over the tip without filing/cutting it off.

    As for mounting, this will be in a swimming pool, why not use several 2" long, 1" diameter tubes around each LED where the wires break out, connecting each "light tube" with the bundle of wires for control. This would allow you to combine the hot glue trick so all of the LEDs would be pointing in the same direction. Glue in a weight of some sort to keep them pointed the same direction and to keep them from floating.

    Reduction in number of wires can be done with Charlieplexing, though a uC (microcontroller) is usually needed to use that scheme, from what I've gathered in the other thread, this will be controlled by a uC, so there shouldn't be an issue. For 15 LEDs, 4 wires.

    I had an idea for another option, which involves keeping the "bundle count" down for the wires. After a series of LEDs, pass off control to another uC to run the next set, which passes on control to the next set, and so on. This could be triggered by all lights being on, or an additional wire pair to use SPI or 2 wire protocol for all the uCs to communicate the speed/sequence. Though this idea does make it technically more complicated, the available options and results are greatly expanded.

    --ETA: Mad Scientist version would be running a fiber optic cable under and tapping out a fiber at each xx feet. This would allow all of the electronics to sit relatively dry on the poolside. It wouldn't be as bright as the LEDs though.

    --ETA2: Use Ping Pong Balls for each enclosure, cut two holes in it, insert LED, pack wires in and out with silicone. That way the entire ball "lights up". Keep a weight on the opposite side from the LED direction so the effect is nice.
    Last edited: Dec 26, 2010
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
    I'll agree with some things said here and in other threads, can you put together a few sketches as to the way these are going to sit in the pool, how you expect them to aim, how you want them to turn on & off etc?

    I know they already sell "light tubes" that are around 25' long but most are run from 120V, you might look at how they assembled those.