Step 1: Introduction
Step 2: Preparation
Searching on-line I found some "super bright" LEDs that were supposed to be balanced to 3400 degrees Kelvin. I ordered 40 LEDs, which seemed like plenty since most of the commercial ones had only about 18 or maybe 24.
To provide brightness control, I divided the LEDs into four circuits of ten each. The lamps use just 3 volts, so I bought four two-battery AA battery holders from Radio Shack, and four of their little toggle switches.
I had a decent piece of aluminum sheet -- it was left-over from a repair my son was doing to an Airstream trailer, but there are sheets at Home Depot that look about the same. It is a little flexible, but plenty strong enough to support all of the components.
I used 1/8" thick acrylic sheet material to build the body, and sprayed it with black paint at the end. Working with acrylic sheet is wonderfully easy -- it can be cut and drilled with woodworking tools, and is assembled with solvent cement that cures in just a few minutes. It is helpful to prepare edges for gluing with a jointer, but a "thickened" cement is also available that will take care of small imperfections in the glue jopints.
But since LEDs do not get hot, the body of this project could also be made of wood. Thin model-maker's plywood would be a good choice. Fiberglass could also be laid-up over a simple form.
It is unnecessary to make the beveled corners shown here, and this adds a lot of work to the project. A plain rectangle shape would work just fine.
Of course, like other LED projects you will need a small soldering iron, and in this case some red, black, and perhaps some uninsulated hook-up wire. Other basic tools will be needed, of course, depending on the materials you choose.
Step 3: Layout
The size of this one was based on the size of the camera sunshade, roughly 4 1/2" X 5 1/2". I added about 1/4" all the way around for clearance, and decided to make the aluminum reflector on which the LEDs are mounted 2" wide all around. The overall outside dimensions ended up being 9 5/8" by 10 3/8". With respect to the depth of the case, I figured on allowing about an inch behind the reflector for all of the components and wires, and about an inch in front of the reflector so that there would be a bit of spread to the individual lamp beams before they pass through the front diffuser. So the depth outside dimension ended up being 2 1/4' which includes the back and removable diffuser.
The lamps are arranged in two rows all around the reflector, and the rows are about 1/2" from the inside and outside edges. This leaves about one inch of space in the middle for the four battery holders, with one on each side. Spacing between the lamps ranges from about 1 1/4" and 1 3/4" with those on the outside row being further apart.
So my advice is to sit down with pencil and paper and and make your own plan. Google's software Sketchup is also great for projects like these if you are inclined to work with software.
Step 4: Construction
Whether you work with wood or acrylic, or some other material like fiberglass, will determine how the basic body is made. After it is finished you can measure and cut the aluminum sheet for the reflector / LED mounting plate. I glued four one-inch long posts near corners on the inside to carry the reflector. Being acrylic I drilled and tapped the posts for machine screws, but wood posts and wood screws would be fine.
After drilling the holes in the reflector plate for the LEDs, which are just large enough for the front part of the lamp, I used a fine sandpaper on a small orbital sander to give the whole front surface a nice, bright, soft reflective quality. I placed the LEDs in the holes making sure that the negative poles of the LEDs were toward the closest edge (either outside or inside of the ring). Then I put a drop of Gorilla Glue on each LED to keep them in place. I also glued each of the four battery holders in place.
On the outside, I also glued posts with tapped holes to use for mounting the diffuser. I finally also made a steel piece from 1/16" thick stock to mount the ring light on the camera shoe. It has four screws fastening it to the top rear side of the body, and the right angle protrusion needs to be made 18 mm wide to fit the standard camera shoe. I was able to attach a flat head machine screw by countersinking the hole and using a machine nut on the top, and made a tapped knob (with a countersink large enough to accept the nut) to clamp down on the camera shoe.
With respect to wiring it all together, it was a bit tedious, of course, but not really difficult.
I wired all of the negative poles (outside edge of outside row, inside edge if inside row) together with plain bare wire, and soldered the two ground circuits together as well. I then attached all of the black leads of all four battery holders to any convenient place on this negative circuit.
I had numbered the LED positions and divided them into four groups of ten, with each group scattered around the entire ring. This way, each circuit will provide shadowless illumination, and the illumination will remain even as more circuits are turned on. Obviously, each circuit must be wired through it's own switch, and I left enough wire on the switch leads so the switches could be installed on the rear of the case before the whole assembly is dropped into place. This is not rocket science.
Step 5: Closing Comments
I forgot to mention the chore of cutting the holes in the back of the case for access to the battery holders. Since the Radio Shack battery holders have slightly curved sides that hold the batteries snugly in position, I took an easy way out and just stuffed black foam into the open spaces.
The front sheet of 1/8" acrylic was also sanded with the fine paper on the orbital sander. This adds a softer quality that is also much easer on the eyes of the subject being photographed.
The LEDs turned-out to be much closer to daylight color temperature than advertised, which is both good and bad news. When shooting in daylight, the light quality looks great, and if even more output is needed, the diffuser can be removed. With the diffuser off, this baby puts out some 40 foot-candles at three feet with no other illumination being present.
For working in tungsten light, using trial and error I matched the color of a #85 color conversion filter on a plain Photoshop file, and printed the color on sheets of clear ink-jet transparency film. It took some fooling around to get the opacity set right. I did see another Instructable for printing color gels for luminaries at a later date.