My husband built the zapper according to Hulda's specifications...he checked it about a week after we had been using it and discovered that he had made an error (I personally think it is not that easy to make...and my husband also soldered instead of using alligator clips for everything outside of the ones attached to the copper hand holds). He runs a construction company and knows a bit about electrical stuff. He then checked it another 3 times. Shortly after, I started passing some pretty big stuff (stones, small rice like parasites perhaps). However, I think I'd like to order the new one dr clark has because it lets you know if the battery is low, and has wrist bands and a timer (I think). If you bought it, or one like it I'd like to know what you think, and if it has brought you any success!