You need to make a coil of wire about 10cm wide, you can do this by wrapping the wire around a circal object like a drink bottle. When winding go for thickness not whith, the thicker the coil the better. When finish wrapping slide it off the circal object and tape it up so it looks neat. Make shore to leave wire to connect it to your switch and power sorce. You should have a nice ring.
Step 2: The disposibul camera
Get a disposibul camera with a flash, take the charging circet out of the case. DON'T SHOCK YOUR SELF. The charging circet has a 330volt capasitor and if it's charged it will hurt. To discharge the capasitor touch the two wires conecting to a black cinider(the capasitor) with a screw driver, it should put out a shower of sparks. Make shore you take out the batteries.
Step 3: Assembly
Attach one of the wires coming off the coil to the switch and the other to one of the wires going into the capacitor. Get a wire going from the switch to the other wire going into the capasitor. When your done charge up the capasitor and when it's charged switch the switch and it will creat an EMP. It should be able to knock out calculators at close range. If not improve the coil with more layers of wire or attach extra capasitors onto the charging circet.