Step 7: Layout of the new lamp
Tape the nice surface of the white board with masking tape to protect from scratches during all the handling required and to provide a surface to draw on. It also helps keep the cutting and drilling neat.
Remember to measure twice and cut once.
A large circle-drawing compass is most handy in laying out the project. Cut the white board piece to a round circle of a diameter just less than the diameter of the light head, my circle was 8.7 inches (221mm). Band saws work great for this, but a scroll saw will work as well.
Layout and draw the inner circle just larger than the lens; do not cut this out until the holes are drilled. I was able to insert my circle partway and used the open lens hole to trace a draft circle. Then I corrected the trace to make this circle a bit larger. My circle was 5.2 inches (132mm).
Ok, here is the tough part. You need to draw the four equally spaced circles that the LED's will be aligned on, then divide the circles evenly depending on how many LEDs you use. Since I decided to make my light strings 2 sets of 30 LEDs in series with each set of 30 consisting of 2 strings of 15 LEDs in series. I needed to divide each of my 4 circles into 15 equal sections. I found that my circles were too close to fit the jumbo LEDs perpendicular to the circles. I tried to get fancy with a spiral effect. Now go do it.
To make it easy to layout the 2 holes per LED I then used a small circle (same diameter as the LED legs are wide) to speed layout.