I need a circuit that switches the positive and negative between two separate terminals at a specific interval. This is for dispersing copper in water for a project that I am working on. I want to reverse the polarity of the conductors so they will be "self cleaning" and I want to prevent bridging. I have seen this done before on a device that put silver in water but I have no idea what the circuit is called in order to do a search for it. Can anybody tell me how this is done.