The first thing I did was draw up a general plan so I could figure out how everything would fit together. The outer diameter of the Arc Reactor is 4", so if you print the plan photo to that scale it will give you a good guide and help you get everything lined up correctly. All the measurements used in the drawings are in inches and they are really just to be used as a guide- I really just eyeballed everything as I was making it. By no means are they meant to be exact measurements. The most important thing is getting the proportions correct so everything will fit together during the final assembly.



The easiest way I found to cut out all the parts is to draw the patterns on paper and then glue the patterns to my sheet plastic or sheet metal using rubber cement and cut the patterns out with a jeweler's saw. Then file all the edges and smooth them with sandpaper.



So let's start by making the outer ring/backplate assembly. Begin by cutting a 4" diameter disc from PCB material. There are two copper traces cut (or etched) into this as well as a couple of solder pads on the center so you can solder down the LED's. There are 11 LED's- 10 for the clear ring and one for the center lens. The LED's I used are a surface mount type part# NTE 30027. Even though they are a surface mount component they are pretty easy to solder to the copper traces.The LED's sit directly under a clear acrylic ring and they are spaced 36 degrees apart- just make sure they are all facing the same direction! I simply connected the LED copper traces to the center solder pads and then drilled two small holes and soldered some wires from the back of the board to go to my 3v battery.



UPDATE!

Instead of having to make a circuit board and solder all the tiny LEDs you can just get some of these little guys and wire them in parallel-

http://www.sparkfun.com/commerce/product_info.php?products_id=8735



Just glue them down to a back plate and you're good to go!



The outer ring was cut from some thick plastic sheet- I used Delrin because it cuts well and is pretty durable. A good substitute would be 1/2" MDF sheet. I should have painted the ring silver but I ran out of time......maybe I'll make a machined aluminum ring in the future. There are 10 2.5mm allen head bolts evenly spaced at 36 degree intervals around the ring. I just drilled a pilot hole, then drilled a countersink for the bolt head so it would sit just below the surface of the ring. I actually threaded the holes for the bolts but you could probably just shove them in there with a bit of glue.



The outer ring is glued to the PCB backplate with a hot glue gun. Then run a bead of hot glue over the LED's and the copper traces. This will protect the LED's, help diffuse the light and keep the circuit from being shorted out when the remaining parts are installed.



Now you need a lens for the center. I made mine from acrylic sheet, but you could use just about any kind of lens or clear plastic part that would fit. The thing to remember is that if it is too tall then it will come into contact with other parts later on so watch the height. I used a scotchbrite pad on the lens to help diffuse the LED light.



Next an old heart rate monitor strap was glued and screwed to the backside of the backplate. The two screws went through the PCB and into the outer ring, helping to hold everything together.

