30 LED Build Log for 12" MakersLED Fixture

In this post we run through the steps we went through to build a 30 LED fixture using LEDGroupBuy.com’s 3-UP Cree LEDs on a MakersLED fixture…

Plan and Map out your Build

  • When you order your LEDs from your vendor, confirm the number of LEDs your LED power supplies (LED drivers) can handle.
  • MakersLED Worksheet ThumbnailUsing a Worksheet Draw and Map the following positions:
    • LEDs, including the +/- solder pad orientation
    • Wire paths – color code different color LED channels
    • Screws Positions- The inner t-slots may be shared between adjacent LED channels and may require twice as many nuts!
    • Where holes should be drilled in the fixture for wiring

You may be able to get away with not planning your build and wire things on the fly, but we highly recommend completing all of the above steps.


Lets Get Started…

1. Prepare the LED mounting screws and slide them into the t-slots

  • The unique T-slot makes it easy to mount leds with standard 4-40 nuts and washersPrepare the screws by installing the nylon washers onto the #4 size LED screws. Install the nut so it is threaded flush with the bottom of the LED screw.
  • Install the LEDs into the slots of the heatsink. Use the screw map you drew up on the previous step. You may consider adding extra #4 nuts in the slots for future upgrades – this could save you some time when adding later.

2. Lay out your LEDs

  • Land the LEDs under the screws but don’t tighten them down yet
  • Use the LED map you drew up in the first step to assist layout


3. Apply a small amount of thermal grease (or paste) and mount your LEDs down firmly using the screws

    • Using less thermal grease is better than using too much. Always try to maximize the metal to metal contact. The thermal grease’s job is to fill in the minute imperfections of the two surfaces. Standing air is a bad thermal conductor. Aluminum to aluminum contact will almost always outperform thermal paste.
    • You will probably make a mess of the aluminum during mounting. Don’t worry, it will clean up later!

4. Cut wires to length and solder your LEDs in a series

  • Cut your wires to length, strip them, and tin them. Do not strip more than 1/16″ of an inch (about 1.5mm). If you strip too much, you may shorten the length of the stripped wire leads after they are tinned.
       
  • To Tin the wires: Applying a little of solder to your soldering iron tip, and then apply the solder to the wire.
    • Be careful – the wire can get hot if you hold the iron on it for too long!
    • Use “Rosin Core Solder” – yes, it contains lead. I picked up my solder at RadioShack. You can go with lead free solder but it will be 10x more difficult to work with. If you use lead solder, wash your hands when finished.
  • Tin the LED pads with a little solder
    • Solder only the pads you need to connect wires to. Use your worksheet showing the +/- LED orientations.
    • Be sure to apply enough heat to avoid “cold solder joints
    • Solder the LEDs in series. This means, connect the + on the first LED to the on the second LED, and so on. Yes, you have multiple pads on the LED to choose from. Since we have already applied solder to the wire and the LED, just get the pad of solder on the LED hot and place the wire onto it until your pre-tinned wire is smothered in smooth flowing solder.
    • Color Code the final wires coming from the plus - minus pads for easy IDAttach a long lead of wire to the first and last +/- LED solder pads so you have enough wire to fly back to the LED driver (power supply). You may consider color coding the positive and negative leads so they can be easily identified later. I used red wire for my LED + side.

5. Test each series of LEDs

  • Take some time to wire up one of your LED drivers to test each series of LEDs. We suggest not moving on until you know every series of LEDs works.

 

  • Note: In this case, I used 20 gauge (AWG) wire inside the fixture for all local LED wiring.

6. Drill holes in the fixture for wire management and power entry.

  • Size the hole so you can install vinyl or rubber grommets for a finished look. These are available at Lowes, ACE hardware, or Radioshack
    • The aluminum is soft, so even an inexpensive set of Black and Decker brand drill bits will work nicely.Drill the holes by locating the drill bit on the built-in indexing groove on the fixture
  • Connect up your LED drivers:
    Solder, wire nut, or use butt-splice crimps to connect your LED series to the LED+ and LED- side of your LED driver.
  • For this build, the LED drivers are mounted remotely under the tank. Upon exit of the fixture, we re-purposed 16 gauge AC extension cord wire to pass the DC current to power to the LEDs. If you don’t over size your cable for the resistance and voltage drop from long cable distances, your LED drivers will not be able to properly maintain the constant current needed to maintain the LED’s long life.

7. Install the Fan

  • Install the fan by installing the 10-24 screws and square nuts, and sliding the fan into the housing. Then, slide it between the upper 1/4" T-slots in the heatsink. Install the screws and square nuts into the fan cover, place the fan into the cover. Slide the fan+cover assembly into the upper t-slots, tighten the screws.
    •  For this build, we used a power adapter with a built-in 4-pin molex power connector to plug directly into the fan connector. For multi-fan builds, we suggest cutting the wires and soldering or wiring nutting the fans in groups of no more than 3 and running a 12v bus wire out to each group of fans.
    • Always confirm your power supply has enough amperage to power the fans. Each fan takes about 0.20A (200mA) of power at 12V.
      1. Note: We have found that the fans can be reliably start run at 9 volts for a lower speed

8. Install the endcaps and upper rubber plugs

  • Remember to Install the fan and nuts before installing the rubber plugs! Don’t forget to include any hanging hardware in the top slot also.
  • Use a small amount of dish soap to slide the rubber plugs into the slots. Be very careful not to slip and cut your hand on the heatsink! If you don’t think you can install them safely, don’t use them! See disclaimer.
  • Use the stainless self-tapping screws to attach the endcaps. These can be easily driven into the end of the extrusion by hand.

9. Fine Tuning

  • Finally, follow the instructions with your power supply to adjust the current (mA) to a safe operating range.
  • If you have a dimming kit or external controller, follow the included wiring instructions.

 


 …Even with the fan removed awhile it runs quite cool!


Last Notes:

Number of LEDs
Read the specs on your LEDs. Add up the forward voltage of all the LEDs in your series and confirm that they do not exceed the LED driver voltage. It is best to leave at least a few volts of headroom since the actual voltage of each LED may vary.  If you don’t know what this means, just check with your LED vendor.

Moving Screws Tip:
When sliding the screws around, it may be easier to use a small screw driver or narrow stick to push them around at the nut location instead of using your fingers. This comes in useful on the 4-6ft fixtures with hundreds of LEDs.

Soldering
In this build we attached the LEDs to the heatsink first and soldered the wires second. For many, this method may be easiest because your LEDs will be securely pinned down and it will leave both hands available for holding the soldering iron and solder. Since the LEDs are attached to the heatsink, the heatsink will quickly sink the heat away from your soldering iron. If you have an adjustable soldering iron and are using lead based solder, set your iron a little higher – to 325C (just over 600F). Note: If you don’t have a good soldering iron, you may consider soldering the LEDs before attaching them to the heatsink, as shown here.

Disclaimer
Bottom Line: You built it, so you are responsible for all aspects of safety. Improper use of tools, extremely bright lights, and electricity may cause damage to yourself or your property. Heatsinks are heavy and may have sharp ends. Use caution when handling.

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4 Comments

  1. How to order? May I have your wiring diagram of LEDs.(all connect in parallel,right) . Power supply for one LED up to …..(per your heat sink).

    • The heatsink can be purchased from LEDgroupbuy.com or LEDsupply.com. Typically, LEDs are connected in series. This simplifies the wiring and also avoids unbalanced LED strings, in the event one parallel LED strand goes down. Our heatsink is capable of sinking over 100 watts per foot. If you had a 48v power supply and each of your LEDs in series use 3v that would provide power for 16 LEDs (48v/3v). Your LEDs driver specifies the amount of current sent through the series of LEDs. To determine watts, multiply 3v by 1amp = 3 w. For 16 LEDs it would be 3v x 16 LEDs = 48w.

  2. Is there a way to add more leds on a different driver after you have installed the initial leds, or do you have to take all the leds off, add these, and resoder them all back on?

    • if you don’t have enough wire slack (or solderless LEDs) then yes, you would have to re-solder. I would recomend leaving some slack and adding some extra nuts in the t-slots if you think you may upgrade your fixture at a later time.

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