I've always wanted one of those flashflight discs; you know, the ones that light up so you can play at night. unfortunately, I really don't like the weighting of them; I can't for the life of me throw a flick with it, and they're a bit expensive. so I decided that I'd make an attachment for my current discraft ultra star that does a similar thing. it's removable, and the only modification you make to the disc is a small hole, which shouldn't make any difference to the aerodynamics. (you could glue a nut to the bottom of the disc, but it wouldn't be as secure.)
Step 1: Get stuff and things
a soldering iron
a CR2016 (or similar) coin cell
a small bolt with corresponding nut
plastic (not pictured)
hot glue (not pictured)
hacksaw (not pictured)
Step 2: Solder LEDs to perfboard
solder the LEDs as shown. make sure they're near the edge, and bend them to a 90 degree angle.
Step 3: Drill hole in board
this step probably should've preceded the soldering, but regardless, you need a hole in the board that's roughly the same diameter as the bolt. make it as centered as possible (I didn't do very good at this part).
Step 4: Tin the bolt head
the bolt is going to become the positive contact for the battery. as such, it needs stuff soldered to it. however, it's pretty hard to get solder to stick to a bolt with a soldering iron. a torch does it nicely, though, so we will coat the entire head of the bolt with solder so we can use the soldering iron to solder wires to it later. make sure to use plenty of flux.
Step 5: Solder bolt into the board
now that the bolt is coated in solder, we can use the soldering iron to connect it to the board. first, solder as much of the bolt as you can to the contacts on the board to lock it in place. after that, solder all the positive leads from the LEDs to the bolt head.