By keno | June 21, 2010
DIY CREE xp-g R5 LED Aquarium Light – Part II
A Word of Caution:
This project involves the use of electricity, power tools, and high power LEDs. Before you tinker with LEDs or any electrical materials, be sure you understand the risks involved. This series of articles was created simply to share what I’ve done. These are not verified instructions. I take no responsibility for any harm caused to you, others, or to your property as a result of the info contained in these articles.
In Part II of this series, I will explain the non-electrical part of this build. The internal parts of the Orbit fixture needed to be removed and there were a number of metal parts that needed to be fabricated to hold the heat sinks together and to hold the heat sinks to the the light fixture housing.
The deconstruction of the Orbit fixture was fairly easy. There were a few screws holding the reflective shield in place. The reflective shield is going to be reused, not to reflect light, but to provide two other purposes. First it will be put back in place to hide the wiring and Meanwell ELN-60-48D power supplies. Second since it will be right behind the fins on the heat sinks, it will provide a smooth path for the air to flow through the fixture for cooling. Once the reflective shield was removed you could see the ballasts and wiring for the fluorescent bulbs. The big plus and I mean big was the aluminum bracket on the left side of the image. The reflective shield was screwed to this bracket to hold it in place. Now the Orbit fixture unfortunately only had two of these brackets. When I placed one of the heat sinks on top of the bracket, it fit perfectly in place within the Orbit fixture. To make this project work I would need more of these brackets (easier said than done). The plastic left end cap, which is where the air comes into the Orbit fixture, would be the place where I would mount my 2 potentiometers and 2K resistors for my dimming control circuit.
The right side of the Orbit fixture is where the 120 volts, the wiring for the moon LED’s, the on/off switches and the 120 volt ac fan sits. It’s pretty busy on this side of the fixture, so that is why I decided to use the left side for the dimming control. You can also see the second aluminum bracket.
The removal of the ballasts and wiring was easy. There were several screws holding the ballasts and wiring in place. All parts were removed and saved.
The 2 aluminum brackets that are in the Orbit fixture fit into a series of channels that are part of the Orbit fixture and the brackets have to be bent slightly to either remove or insert them. Once they are in place it takes quite a bit of force to pry them loose. A number of these would definitely hold the weight of the heat sinks in place. Remember once the heat sinks are in place and the unit is turned over, gravity will be pulling down on the heat sinks. That is the one negative of this fixture the weight of the heat sinks. So I went to the internet to see if I could find the brackets as a replacement part from Current USA. No luck. I called Current USA about the brackets, they would not sell them to me. At the same time I also tried to purchase just the empty housing from them for future projects, again no luck. So I decided to call a metal fabricator in my area. I sent him some images of the aluminum bracket along with the dimensions. I felt that I needed 8 of the aluminum brackets. Price to fabricate the 8 brackets, a whopping $230.00 dollars! Forget that. So I went off to my local Lowes hardware store and picked up some aluminum flat stock (1/16 x 1-1/2 x 8′) for $12.00. I was hoping to find the flat stock in a 2″ width but had to settle for the 1-1/2″. The original bracket measured 1/16″ x 2″ x 6-1/4″, with the bends at 3/4″. As far as the angle of the bends, I decided to just bend the new pieces by eye and match them to the original piece. I would bend the new pieces by putting them in my vise and applying pressure with my hands. I took out my hacksaw with a diamond circle blade and started cutting. Since the widths on these were smaller I went ahead and made 12 of them. In the end I only needed 10 to make the fixture work.
Creating the Heat Sink Assembly
Well with the aluminum brackets made I was now on to figuring out how to mount the heat sinks to the brackets. For this fixture I went with heat sinks that were 5″ wide and 6 of them. The fixture is 48″ long. I figured I would leave 1.5″ on either end of the fixture for a total of 3″. This space was needed for the fan on the one side and the dimming control on the other. That would leave me with 45″ for my Heat Sink Assembly. Using 6 heat sinks at 5″ each (30″) that would leave me with 15″ of empty space. If I spaced the heat sinks 3″ apart that would cover the 15″ of empty space, perfect. I could have mounted each heat sink to 2 of the new brackets that I made, but that would mean a lot of alignment issues and drilling through the heat sinks and long screws to hold it all in place. Instead I decided to get 2 lengths of aluminum angle stock (1/16″ x 1/2″ x 8′). I would cut 4 pieces at 45″ each. I would put 2 pieces at the top (fin side) and 2 pieces at the bottom (non-finned) of the heat sinks to form one unit with all 6 heat sinks spaced 3″ apart. This way I could handle and position all the heat sinks as one unit. Plus I could drill through the aluminum angle stock into my brackets that I made. This would make for a strong secure bond between the heat sink unit and the brackets to the Orbit housing. On the finned side of the heat sinks, I decided to mount the angle stock on the inside part of the first fin. I did this to make it easier to drill the holes through the angle stock into the aluminum brackets I made. Going back to the reflective shield I saved, the shield would be placed between the heat sink unit and the brackets, which would hide all the brackets and the wiring and the power supplies. Plus provide for the air flow through the heat sink fins. Also before I assembled the Heat Sink Assembly I marked, drilled and tapped all the holes in the Heat Sinks for the LED stars on my drill press.
With the Heat Sink Assembly built and mounted in the Orbit Fixture, it was now time to put together the LED’s, Power Supplies and the Dimming Control Circuit. That brings us to the next part of this series Part III. In Part III of this series, I will explain the how I put together the LED circuits, the dimming circuits, the testing and current adjustments I made to the Meanwell ELN-60-48D power supplies, re-installation of the moon LED’s and reassembly of the Orbit fixture.