* Two strips of white rags approximately 12 inches wide.
* One flexible plastic ball (approximately the size of a softball).
* A few strips of twine or string.
* One 1K (1,000) Ohm resistor.
* Two red LEDs each rated 3 volts with 20mA leads.
* One SPDT (single pole double throw) heavy-duty switch.
* One 9 volt battery.
* One 9 volt battery snap connector.
* One small eye hook.
The plastic ball was from an old ball pit. It worked well because it was flexible -- unlike a Wiffle ball that is a harder plastic. You also only need a small strip of twine, but I just threw the whole spool into the picture. Finally, the toggle switch is heavy-duty, and you could probably get by using a SPST (single pole single throw) push button switch.
Step 1: Cut Openings and Eye Slits in the Ball
The first step is to cut approximately 1/3 of the ball off at the base. You want to maintain a round shape, but leave enough room to place the components inside. I also cut two slits for the eyes and one hole on the opposite side for the switch. You can see a small opening on the top that I poked through so that I could attach the eye hook for hanging.
You'll find that it is best to do a rough estimate on how far apart you want the eyes spaced. You don't want them too close because you don't want the wires to cross when placed inside. However, you don't want them too far apart because you don't want to stress the solder joints. Also, instead of cutting holes for the eyes, use a utility knife to cut small crosses. Then poke the LEDs through. This provides grip.
Step 2: Solder the Electrical Components Together
I don't have a circuit diagram for this, but it is a fairly simple series circuit. You can't tell very well from the photograph, but you want:
1.) The negative lead from the battery snap to go into the center ground lead on the switch.
2.) The resistor to be soldered to the negative lead on the first LED.
3.) The positive lead on that same LED should be soldered to the negative lead on the second LED.
You should obtain full brightness since the resistor will impede 3 volts, while the LEDs in series will require 6 volts (3 each). That equals the capacity of the 9 volt battery.
Step 3: Place the Entire Circuit Inside the Ball Opening
If you didn't cut your eye slits the correct length apart, then this can be a frustrating step. It requires reaching in and bending the leads on the LEDs or resistor to get a good fit, ensuring the LEDs don't come loose. The benefit of this heavy-duty switch is that it has a washer and nut that you screw on the outside to secure it to the ball.
Before moving onto the next step, be sure you have a good connection, and attach the battery to the snap connector. The weight of the battery will offset the weight of the switch, and it should balance nicely. If you're happy with the fit, you may want to hot glue the battery inside the ball to the opposite side of the switch.
Step 4: Tie the Rags Around the Ball and Add Finishing Touches
The final step is the easiest. Put the rags over the top of the ball, and then mark with a pencil where to cut slits for the eyes and a hole for the switch to poke out of the back. Alternatively, the LEDs don't generate much heat, and you could simply cover the entire ball. The eyes glow brightly through the cloth (depending on the thickness).
Now attach the eye hook, and tie off around the base just tight enough so the loose battery doesn't fall out of the hole. Then attach a string to the eye hook and you're ready to scare the family or neighborhood kids!
Please note: This is not a waterproof instructable, so if you want to hang it outside from a tree, I strongly suggest you use a hot glue gun to seal around the eyes and the switch before placing the cloth over the ball.