One thing I found annoying when experimenting yesterday was the need to walk to the dropper, release a drop, walk back to the camera to see the result, adjust the time delay, and repeat. Rummaging in my junk box I found a motor that seemed perfect for building an automatic dropper, and this is the result.

I'll set it up so that it's driven by the microcontroller so that it can shut off after each drop, and restart after a suitable delay. There is also potential for capturing multi-drop pictures, I suppose...