For what its worth here is one of my early dippers.
It has 2 wires very close together that are both struck by each drip at the same timeThe drip falls directly between them
connecting them very briefly.

I found this dripper worked great when it worked but ...
1. It was very sensitive to being perfectly vertical
2. Every once in a while water would actually bead between the to wires leaving them connected.
3. It was tuff to get a good seal that looked good and was reliable.
4. I couldn't adjust the drip size
5. The wires corroded very quickly.

2013-10-30 22.34.12.jpg

2013-10-31 03.13.53.jpg