How to to build a rim detector??

[drumdhiver]

Hi all,

I try allkind of rim detection, and it don't gives a good result...
See this manufacturer :

http://www.682drums.com/DT2-PRO-drum-tr ... 16152.html

look this photo on bottom and left

http://www.682drums.com/images/P/DT2-Pro%20trigger.jpg

Have you got ideas about rim detection systems ? about electronic circuit shem which preconditioning a rim sensor?