When building prototypes on breadboards I find it useful to have small pre-made components such as 3.5 stereo jack sockets configured to fit breadboards
The 3.5 stereo socket is attached to a small piece of board and the connectors from the socket attached to pins that fit in to a breadboard.
Red is VCC, black is ground, and white is the centre channel or data
I also create mini boards that have more than one component
These have female or male headers and can be connected using standard breadboard wires
In an early version of the camControl device (before the dropController) I used an interrupter/optoisolator to detect the water drops. The plan was to detect the water drop, wait a little bit and then activate the shutter.
There are various different kinds of photo interrupter, different shapes and different sizes but all do the same job.
A photo interrupter has a LED at one side (normally IR) and a photo transistor at the other. When the LED in emitting light the photo transistor allows a current to flow. Remove the light and the current stops.