NOTE! Don't hit anyone with this and only aim for the foam target!
Step 1: Gather Materials and Tools
1. Foam Insulation - grab a sheet of 1/2" thick foam insulation at least 12" x 40".
2. Bare Paint - the pen works better but you could also use the bucket and brush.
3. 1 Paper clip - better if bare metal instead of the plastic covered kind like I used.
4. Roll of Gorilla Tape - nice and super sticky!
5. Length of 1/4" wood or metal rod - to add stiffness to the sword at least 38" long.
6. LED - any color LED you want.
7. Small jumper wire - you won't need this if you used a bare paper clip.
8. 4x 3V button cell batteries - CR2430 size. I had a box of these laying around.
9. String or Lanyard - to hang the target around your neck.
1. Trusty pocket knife.
2. Jigsaw. (Optional to speed up cutting out of the sword but could be all done with time and knife.)
3. Claw hammer - any hammer will do. Even a rubber mallet!
Step 2: Trace and Cut Out the Sword
I had already made a wooden sword before so I just laid that sword on the sheet of foam and traced it with a sharpee.
After you have a nice trace of a sword or just freehand drew one yourself about 38-39" long and about 8" wide at the fancy handle simply cut it out. I used a jigsaw with the foam clamped to a table and cut close to the line but not right on it. If you were more in practice with a jigsaw than me you could probably do it right on the line and save some time.
Then once the sword is out you can use your trusty pocket knife to trim it down to right on the line. Boom! A nice foam sword. Next we'll add some strength so it doesn't snap in half when we hit someone with it.
Step 3: Add Reinforcement
Use your trusty knife to trim out just enough of the foam to sink the rod but be SUPER CAREFUL not to cut all the way through and split the sword in half!!!!
Once the rod is sunk almost flush (I was afraid of splitting it in half so I didn't sink it all the way) take 7-8" long strips of Gorilla Tape and wrap it nice and tight around the the sword at the handle, near the bottom of the blade then near the tip of the blade. Pay extra attention to the handle to give yourself a nice grip.
Finally take the conductive paint and draw zig zags down the edges of the blade. This will make contact with the target "fingers" later and close the circuit connection on the target lighting up the LED.
Step 4: Make the Target
NOTE: "the battery" mentioned below is all four button cell batteries together stacked in the same order +, -, +, -, etc.
Cut a 7" x 3.5" rectangle from the leftover foam board for the target. Stab the legs of the LED into the foam at the opposite end from the target making sure to note the positive and negative leads by carving it in the foam with a sharp tip like a pencil. Use the Bare Paint conductive paint to draw out a target of interleaved "fingers" that are attached on the left and alternatively right sides where they are close (I left 1/8" of an inch between each) but do not touch at all! Then draw the circuit out with the paint so that one side of the target connects to the positive side of the coin cell battery and the other side of the target connects to the positive lead of the LED. Then paint more of the circuit from the negative lead of the LED close to but not too close to the battery since the positive part of the battery wraps all the way around it.
Place a battery on the foam and trace around the battery then use the pocket knife to carve out a shallow hole to place the four batteries. Then paint out the circuit for the positive side of the battery so that it dips down into the center of the shallow hole.
If you have a bare metal paper clip you can skip this step.
Take a small piece of wire such as a small jumper wire from a hobby wire kit used in prototyping on a breadboard and stab one side into the end of the painted circuit from the LED negative lead that stopped near the battery. Then bend it so that once the battery is placed inside the shallow hole you carved for the battery it will touch the negative side of the battery.
Straighten out the "large" end of the paper clip. Then stab the straight piece all the way through the foam making sure not to press too hard and snap the foam in half! If you have a bare metal paper clip then stab it through the end of the painted circuit that connects to the negative lead from the LED near the battery so that when rotated around it will touch the negative part of the battery and the circuit. If you have a plastic covered clip then stab it through another part of the foam away from the painted circuit. Then make sure the "small" side of the paper clip is sideways and even with the top of the battery hole. Bend the straightened part of the clip on the bottom of the target so that it tries to press back into the foam giving it a spring force to hold the battery in the shallow hole you carved out.
Place the battery into the hole you carved out with the positive side down then rotate the paper clip in place to hold the battery in place. If you had to add the jumper wire because you have a plastic covered paper clip you also need to rotate or bend the jumper wire to touch the negative side of the battery.
Step 5: Test and Play!
Attach a string or lanyard to the two corners of the target away from the drawn on target side by stabbing two more paper clips through the corners. Then you can tag the target with the sword and watch the LED light up to know you've been tagged!