I have two cheap so called bite alarms. They are only good for shark fishing because normal size fish can't trigger the alarm. Even cat fish couldn't.

So, I'm think of creating a simple carp bite alarm. I stuck on the sensor part. What would you recommend? PC mice rotary encoder is not good for this. To use a reed sensor the cercuit needs to be modified, which I don't want to mess with. Any other ideas?  Thanks.

Discard all the parts in the diagram, and substitute your hand on the rod as the "sensor." Nothing is more sensitive than that.

What ever happened to little bells clipped to the rod tip?  I rarely fish bait, but when I do, for trout, I hang a bobber from the line in front of the reel and pull enough line off to almost touch the ground.  When the bobber begins to rise, I've got a bite!

My uncle taught me to put a small stick or a little ball of mud onto the line between the first guide and the reel. When it starts to rise, you know what to do. Some guys will double over their line and clip on a cheap bobber on just the bottom so it's only clipped on once. When a fish bites the bobber raises and you can set the hook and it will often pop off then or a quick pull removes it and you can fight the fish. 

How have/light should be the bobber to be sensitive enough to see a strike but not a wind or waves action?

Are you looking for this to be something to use while trolling or like is it just for carp and bass and stuff.

Are you looking for this to be something to use while trolling or like is it just for carp and bass and stuff.

Just for carp.

Take a blow in the dark bobber(if you are night fishing) and attach 1 or 2 brass bells to the bottom.

Fasten a clip to the top of the bobber. It works better if you actually put a larger clip of some sort on the bobber yourself rather than using the bobbers fixture it comes with. kind of like the same type of clip that comes on those ice fishing weights that slide down your line to find bottom depth. Open the clip and put it on your line in between the top guide and the guide below. When you get a bite, the bobber will jump and the bells will go off. Unclip the bobber and wait for the fish to take your bait before you set. 

if you had a bettter diagram i could help you . if you want to be really techincal you could build one using an arduino and a motion sensor like this http://www.adafruit.com/products/189?gclid=CJ6ksN_2n8UCFRNafgodLgMAvw but that requires too much electronics for the outdoors.  teh best thing is just get some fishing rod bells. http://www.psfishing.com/double-rod-bells.html you are overthinking it.  

if you had a bettter diagram i could help you . if you want to be really techincal you could build one using an arduino and a motion sensor like this http://www.adafruit.com/products/189?gclid=CJ6ksN_2n8UCFRNafgodLgMAvw but that requires too much electronics for the outdoors.  teh best thing is just get some fishing rod bells. http://www.psfishing.com/double-rod-bells.html you are overthinking it.  

I guess I will go with the bells. Hope it is sensitive enough for carp because sometimes they are to shy.

Carp can be very light biters.  I'd use your fingers like J Francho said.   It is what I use, that and watching the bend in my line.  I have had lots of carp bites that would never trigger a bell