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Thread: Eaves LED lighting project.

  1. #1
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    Default Eaves LED lighting project.

    Hi all. I joined the forum to learn about making my own set of lights for the eaves around my house. I read MikeM's, Asimba2's, and now Idleprocess's threads on their designs for a DIY.

    After asking lots of questions from people here and people who sell the LEDs, I've started to get my materials together and assembled. Not complete yet, though.

    First a little background about myself. I've never really soldered before and don't have much knowledge of electrical stuff. So I had to do a lot of reading and ask lots of questions. I THINK I've got enough to get these lights to work and without be a safety hazard. Don't be afraid to tell me if I'm doing something awkward or wrong.

    I've already observed my house's eaves/soffits really closely. To set up the wiring would be simple. I'll get the drivers and dimmers located inside the house just to keep them from getting hot in the summers and for easy access.

    As for the fixture, that's what I focused on a lot. My soffits are vinyl. I don't know exactly what temperature they'll start to deform and burn so I've used some PVC caps between my heat sink and the soffit surface to possibly keep some of the heat off the soffits (Would that help?). I think the PVC makes it look more like a regular light fixture you'd find at the store.

    I just noticed that I don't the screws holding the PCB star to the heatsink in the photo. Presently, I do have two screws in at the two threaded spots on the heatsink. I have the solder joints and the screws planned in that layout to help keep the lights from charging. I'm thinking about spreading some liquid electrical tape on the joints and maybe the screwheads too to be safe (Good or bad idea?).

    (The fixture shown above was one of the first ones I soldered so if it's a bad job, it's about my second time soldering anything ever. The other ones should be better.)



    In between the PCB star and the heatsink, I laid a thin layer of thermal grease. I'm thinking about getting small glass jars about 1.5 oz to enclose some of my fixtures for comparison. Would it be okay to place the tin lid between the star and the heat sink? or would the tin disrupt the conduction of heat from the PCB star to the aluminum?

    So waddaya think? Good idea? Bad idea? Let me know if you can help.

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    Flashaholic* JamisonM's Avatar
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    Default Re: Eaves LED lighting project.

    thumblessprimate, welcome to wild world of soldering! First off, the wire you're using is unnecessarily heavy. That LED is rated for 1A. The largest size wire I use in all my projects is 24awg. As long as the screw heads don't touch the unused solder pads, you should be okay. I wouldn't put a tin bottle lid between the LED and heatsink. Cut a hole into the lid that the star will fit and a couple of others for the screws that hold the star to the heatsink. Dab some liquid electric tap on the all the solder joints and let dry. Mount the tin lid and mount the bottle. You can also take some clear acrylic spray paint and sputter the outside of the bottle so it acts as a light diffuser.
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    Default Re: Eaves LED lighting project.

    Thanks for the tips Jamison! I know I'm doing some just basic soldering, but it's so fun.

    Idleprocess pointed me in the direction of some aluminum jars so I'll likely use that material instead. That way I'll have the stars on aluminum only.

    As for the wire, I thought it might be unnecessarily heavy, but it should still be okay, right? I got a bunch of the 18 gauge solid copper wire.

    I'm going to do some testing of the naked lights (without any seal or cover) today, get to know my multimeter and adjust the dimmable driver I got. This will be fun.

    Keep the love/advice coming guys. Thanks.

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    Flashaholic* JamisonM's Avatar
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    Default Re: Eaves LED lighting project.

    thumblessprimate, nothing wrong with that wire, just that it's much larger than it has to be. Smaller gauge wire would be easier to work with and solder.
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    Default Re: Eaves LED lighting project.

    An update. Nothing too exciting. I just got my aluminum canisters at my door step, and I got around to putting one to use.
    http://i43.photobucket.com/albums/e4...s/IMG_7150.jpg

    Thanks to the suggestion of using them by Idleprocess. They add additional height to my fixture more than I would like, but I can deal with that. This is my set up for testing the lights out, calibrating the SVR2 on the dimmer, and for my own pleasure to see them light up.
    http://i43.photobucket.com/albums/e4...s/IMG_7144.jpg

    It was a little tedious at first to get the XR-Es and wire in the way I would like at first but I think it'll get easier for the later ones after experience with the first canister.
    http://i43.photobucket.com/albums/e4...s/IMG_7147.jpg

    (I resized them to be smaller but they look huge for some reasons to me. Kept looking huge after several tries so here are links substituted in.)

    As always feel free to give me any suggestions.
    Last edited by thumblessprimate; 07-22-2012 at 08:34 PM.

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    Flashaholic* idleprocess's Avatar
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    Default Re: Eaves LED lighting project.

    I'll second JamisonM's suggestion - 20-24 gauge stranded wire is a lot easier to work with than heavier, solid wire. It can carry more current as well, but that's not an issue with your setup. I made the mistake of using some 18 gauge stranded for a recent project with LED tape ... I'm still amazed I didn't rip off any pads or traces.
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    Default Re: Eaves LED lighting project.

    Thanks for the advice. I'll definitely consider using a smaller wire in future projects, but as for now I'll stick with this wire. It hasn't been very difficult for me to work with, but that may be only because I haven't worked a whole lot with smaller wire and done any huge projects. I would only switch to a thinner gauge wire at this point only if it makes a significant difference in the performance and quality of the fixutures.

    Don't get me wrong, I really appreciate your suggestions even though I'm going to stick with my materials at this point. (It might also have a little to do with my male stubborness with not wanting to change). I'm happy to have your support.

    BTW Idleprocess, by your concern of "ripping off the pads", are you referring to the possibility of that happening when you mechanically manipulate the soldered wires to the PCB stars? If so I was concerned about the same thing at first, but I took extra care to apply pressure with one hand on the solder joint while manipulating the wire with the other. With use of the canisters I'm forced to do most of my manipulation of the wire before soldering so it's even less of a concern now.

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    Flashaholic* idleprocess's Avatar
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    Default Re: Eaves LED lighting project.

    Yes. I have removed solder pads from MCPCB (ie "star boards")-mounted power LED's through excess manipulation. With LED tape, the solder pads and tracks aren't so sturdy as MCPCB traces, so excessive manipulation is an even greater concern.

    I do a lot of projects with what I happen to have on hand - even if it's suboptimal - so I can relate. Not too long ago, I discovered that I had used an entire sheet of nice heavy-duty plywood for templates and miscellaneous low-grade project functions rather than cheaper particle board or a lesser grade of plywood because it was on-hand and I wanted to get moving on the project rather than drive 5 miles to the hardware store and obtain something more appropriate.
    I apologize that this letter is so long; I did not have time to write a short letter

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    Default Re: Eaves LED lighting project.

    Would it be okay to place the tin lid between the star and the heat sink? or would the tin disrupt the conduction of heat from the PCB star to the aluminum?
    The thermal conductivity of aluminum is about 250W/(m.K) at 25C, while tin is only 67W/(m.K), doing so could create a thermal bottleneck. Any container or medium that could eliminate airflow to your modules can and well severely lower the effectiveness of your heatsinks. Air is very insulating when it is still, placing a heatsink in a jar and it would act exactly like a block of aluminum, it will sink the heat it absorbs but have no way of dissipating it. In your case, dissipating it fast enough to prevent a fried LED

    CREE XRE at 1A is about 3.7W... those heatsinks look as if designed for 1/2W LEDs. I would make one assembly and test it for long term thermal stability before continuing with more units. Monitor the heatsink with a thermometer [not your hands, tongue, or toe], if the temperature zips up greater than 120C [250F] and fails to stabilize, shut it down. Once the emitter junction temperature of Tj = 150C is reached, the LED will fail. The junction temperature will always be slightly higher than the heatsink temperature, so keep that in mind

    Quote Originally Posted by idleprocess View Post
    I'm still amazed I didn't rip off any pads or traces.
    I learned [through the hard way] that the solder pads on the 20mm stars are by far more resilient to separation than the 14mm and 16mm pads. And when soldering LEDs in a string, leave at least 6" more of slack between the planned distance between units, it makes wiring and patching easier.
    Last edited by Illum; 07-23-2012 at 06:50 PM.

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    Default Re: Eaves LED lighting project.

    Thanks for the input Illum.

    I decided not to go with the glass jars, but rather the aluminum canisters in one of the links in the last previous post. The heat sinks are on the outside with fins pretty well exposed I think. Only the PCB/emitter is enclosed in the canister and I made sure that the PCB star, aluminum canister, and heat sink are in good contact with a thin layer of thermal grease in between the three parts. Would you think that sufficient then for heat dissapation or would there be some damaging amount of heat trapped inside the canister that would affect the PCB/emitter?

    About the heatsinks, I got them from RapidLED where they were listed for 3W LED on 20mm PCB stars. I would guess that the amount of surface area exposed to air is comparable to the aluminum C channels I've seen others use, but I could be wrong. Running at about 620mA the heat sinks definitely got hot in an hour. And running at about 350mA for about 5 hours the heat sinks felt cold to the touch.

    I know you mentioned that I ought to test with a thermometer. Is the method simply putting an oral-under-the-tongue thermometer to the surface of the heat sink while light on for a while?
    Last edited by thumblessprimate; 07-23-2012 at 07:24 PM.

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    Thread Killer Illum's Avatar
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    Default Re: Eaves LED lighting project.

    Quote Originally Posted by thumblessprimate View Post
    And running at about 350mA for about 5 hours the heat sinks felt cold to the touch.
    Neat! Good to know, I might use them for low current products. Didn't think they are up to the task

    I know you mentioned that I ought to test with a thermometer. Is the method simply putting an oral-under-the-tongue thermometer to the surface of the heat sink while light on for a while?

    I was kidding about using your tongue. Lacking proper tools [Fluke 50...] what I did was drill a hole on the heatsink being tested close to the bottom of the LED. The diameter of the hole was about the same size as the probe thickness of a digital laboratory thermometer [DT510LAB or similar]. Insert the probe and backfill with thermal compound. Set the heatsink in the environment where your LEDs will be exposed to. Put something over the LEDs to protect your eyesight, but not over the heatsinks. Power it on and record the temperature read out on a piece of paper at every 10 second intervals. Just for safety sake, round up on the values to whole numbers. Repeat for the next 10 minutes [getting roughly 60 readings, which is already quite a chore]. Open microsoft excel and plot your readings [Quite a chore too]. If in the last ten minutes since t=0 the temperature just keeps ramping up, your heatsink is too small. Sometimes, if the temperature is obviously increasing at an alarming rate, skip the plotting part and try a new heatsink. What you are looking for is a heatsink that will warm up fairly slowly and stabilize into a gentle right hand slope... which eventually the temperature stabilizes, thats your sweet spot.

    If it makes you feel better, I haven't found that sweet spot yet

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    Default Re: Eaves LED lighting project.

    . I think you misunderstood me. I didn't mean to say that I was going to test using my tongue. I meant a sublingual household item type commonly used to detect fevers. It seems the type you mentioned is pretty pricey. Around $50 or more?

    Edit: Seems like $200+
    Last edited by thumblessprimate; 07-23-2012 at 08:48 PM.

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    Default Re: Eaves LED lighting project.

    Quote Originally Posted by Illum View Post
    Neat! Good to know, I might use them for low current products. Didn't think they are up to the task
    Woops I missed a reading a few posts.

    Yeah. I'll get a more specific reading on the multimeter later this evening. I only set the SVR2 to allow a max of about 620mA, and ignored attention to the lower settings. I just wanted to prevent myself from accidentally running these lights too hot and killing the them. I'll likely just run them at 350mA as the goal is low watt low cost security lighting.

    @ Idleprocess: I'm wear nitrile gloves when handling the PCBs and apply some pressure just enough at the solder joint to prevent the joint from being damaged. I guess my wire bending instinct and technique comes from my experience working with bonsai. I use a lot of 14 to 12 gauge copper wire for manipulating branches.

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    Thread Killer Illum's Avatar
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    Default Re: Eaves LED lighting project.

    Quote Originally Posted by thumblessprimate View Post
    . I think you misunderstood me. I didn't mean to say that I was going to test using my tongue. I meant a sublingual household item type commonly used to detect fevers. It seems the type you mentioned is pretty pricey. Around $50 or more?

    Edit: Seems like $200+
    Yeah.. I can't afford a fluke either. An oven thermometer doesn't react quickly enough to the heat gain and would require the user to do a hefty bit of differentiation between one analog ticker and another. I tried a body temp thermometer and quickly learned that it averages its values and then compares it to an internally preset "human body temperature" and then gives its readings. I keep getting "high" on the readout without an actual value. This is the thermometer I used for my heatsink tests
    http://controlscentral.com/eCatalog/...5/Default.aspx
    $20.37 / Free Shipping

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    Default Re: Eaves LED lighting project.

    I got my lights up. I skipped checking any temps, otherwise I'm afraid I'll never get them up and running. Put up the first circuit that runs the back of the house last week, and just yesterday I wired and ran the ones on the sides and front porch of the house. I set the max at 350 mA, but I usually run them at less than that as at 350 mA seems make them brighter than necessary.

    The porch area, I used two XP-Gs.




    This is how they look mounted on the soffits.


    I'd like to get some landscape lighting later to point from ground upward at the front facade. This was pretty fun, and I thank everyone for their advice and knowledge.
    Last edited by thumblessprimate; 08-21-2012 at 04:31 PM.

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    Default Re: Eaves LED lighting project.

    Quote from OP "I'd like to get some landscape lighting later to point from ground upward at the front facade...."

    On a brick house green CREE XR-? look spectacular. I have used green XR-C for this in simple spots from DIY "make your own led bulb kits". It's very eye catching and adds atmosphere to the house. Good work.

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    Default Re: Eaves LED lighting project.

    The light that looks greenish back there is actually from the two-three story apartment behind my backyard fence. In real life, it appears natural or cool white. Not sure how it showed up green. I do have a couple of natural whites, one at each of the fences on the side of the house. I had to replace a couple of XR-E warm whites that I broke with some natural whites from a local LED shop. I get so easily distracted from what I'm working on when someone talks to me. Anyways, they natural whites looked fine at the fences and I can always replace them with warm white later. Thanks for the support.

    @ StefanFS: Rereading your post again. I think you might have been suggesting that I try green LEDs? mmm. Yes I think I might like some green LEDs, but would like to see how it looks first. Perhaps if you have a photo, I may be more inspired to try that out.

    Thanks!
    Last edited by thumblessprimate; 08-22-2012 at 04:43 PM.

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    Default Re: Eaves LED lighting project.

    Nice work, I love my DIY Cree eave lights; easily one of the best things I have done to my home.

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