It sounds like a fun project, but I’d just go out and buy the Bird-B-Gon if I were you. You’re not an electrician, and if you are successful in building something that is nasty enough to hurt the birds, it could be nasty enough to kill you by accident while you are rigging it up. Not worth the risk to save a few bucks, if you ask me.
Give up on the electricity and try what we have used for years.
Get a pellet gun and study the gaggle of the damn birds (hate em). Look for the dominate male, usually larger and can be spotted by his attitude. Employ pellet gun and the gaggle wil leave and won’t come back. The next year some more will show up but just stay current on target practice.
BOOKbump