I decided to add a watt-hour meter to track the power usage on the light head. This module has a current transformer that will be placed around one of the incoming power wires to monitor current draw.
The control panel parts are ready for installation...
The operation of the light will be pretty straightforward. There is a main power switch (to the left) and five diode bank switches that will control the five horizontal rows of LED chips.
At this point the two side panels and bottom panel were cut and fitted to the chassis rails with 8-32 hardware.
The next step was to set up the glass lens or crystal that will protect the COB chips from dirt and physical damage. This 10 x 10 x 3/16 borosilicate glass sheet is resistant to thermal shocks which will prevent uneven temperature changes from shattering the glass.
I set the glass on four COB chips to evenly space the glass off of the heat sink. I then cut out four pieces of 3/4 aluminum angle to be used as a lens bezel.
8-32 screws were used to attach the bezel pieces to the heat sink as seen below.
The next step was to lay out and attach the 25 COB chips to the heat sink. A even coat of Dykem was applied to help reveal the scribe marks in the aluminum.
I measured the chips mounting holes at 34mm square (1.3385) and then layed out the center rows...
To get the closest spacing of the chips I needed to trim a little of the power tabs that stick out of the sides. You can see a trimmed example below (bottom center).
After trimming the tabs on the chips I decided a 48mm spacing pattern would work best and scribed the rest of the heat sink for drilling. I then mounted the heat sink onto the mill table and squared it up for drilling.
I chose to use 4-40 stainless screws to attach the LEDs which required a #41 sized drill for the tap.
I drilled 50 holes on the one side and them flipped the heat sink around to get the bottom half of the 50 that the mill could not reach (not shown).
I now started tapping out the holes with a 4-40 HSS tap and some cutting fluid. It took a while but I managed to do it while only breaking one tap in the heat sink :O/ That was a fun one to remove (not shown).
Now that the hard part of tapping the holes was over I went back over to the mill to drill the 50 holes for the wires that will connect to the COB chips. These holes needed a custom layout which was centered into the flute spacing of the heat sink so the wires could pass through.
I now cleaned up the finished product with some Brakleen and prepared for assembly of the chip array.
I used a bead of thermal paste between the header blocks and the heat sink to help conduct heat better between the parts before assembly.
The COB chips could now be attached with a small dap of thermal paste to help waste heat to escape into the heat sink.
All of the chips were now secure and I had to wonder if this heat sink was going to be big enough to cool them efficiently?
To attach the drivers to the chips I used 22 gauge silicone wire which is excellent for high temperature use.
The wires were threaded through the heat sink and soldered to each LED chip.
Resin epoxy was then used to seal where the wires pass through the heat sink. This will keep cooling air from passing dust into the lens protected area of the light head.
Next I installed a set of five Molex connectors, one onto each of the five banks of diodes. Theses connectors will make the whole heat sink assembly removable from the light head for service.
Once the heat sink was reattached to the frame rails a foam rubber seal was added to the heat sink to help keep dirt out of the chip array.
The aluminum bezel was now reinstalled over the glass for a fit check.
