Circuit diagram
After the successes and failures of the original Sphere of Power, I decided it was time for a definitive upgrade. The Evil Twin is the Sphere of Power's meaner sibling. It uses a digital 3d accelerometer (Hitachi H48C 3-Axis Accelerometer) connected to a BASIC2 stamp to recognize freefall, and then sends out a pulse through transistors to a transformer to deliver a longer shock and have superior sensitivity to acceleration.
The H48C accelerometer is only used to test for freefall, so all that is necessary is to have pin 3 connected to ground (Vss on the basic stamp homework board I believe) and pin 6 to +5V (Vdd). Then pin 4 on the accelerometer is connected to input pin 1 on the basic stamp (this is arbitrary but the program code below expects it also). Then the pin 0 on the basic stamp is connected to gate of an NPN transistor, which is also connected to ground (Vss), and has a high voltage transformer (not necessary to be designated as high voltage but makes a better shock, in either case this should be primary winding) in series connection to +9V which is Vin on the BS2 homework board. I used two NPN transistors in parallel to handle the current. The diagram below should outline the principle, sorry about the bad quality.
Circuit diagram
A really bad photo of the actual circuit
The program file for the BS2 can be downloaded here. It assumes the pin configuration described above so edit that if you changed stuff.
The Evil Twin completed
The Evil Twin worked very well but succumbed to wear. The digital controls clearly set it apart from the original Sphere of Power. Even though the outside of the styrofoam was painstakingly hardened with a plastic coating, it took a few hits and eventually the two halves could not stay together very well. To add to the problem, foil was used as the outer metal through which the shock was sent, and it was next to impossible to connect a wire to the aluminum foil in a way that it would stay attached during regular use. The electrical side worked very well and gave a good shock but due to mechanical wear the project had to be discontinued.