I would like to make a "wake up machine" with my son. It would have a small solar panel with a small doorbell. Can I just hook up a 6V solar panel to the bell with a capacitor in between, once the cap is charged it rings the bell?
You should leave the solar charging to a professional circuit, and instead have a comparator with a potentiometer and a photoresistor, so the bell turns on when there is just the right amount of sunlight. (Bear in mind the fact that you will need a large enough battery and the sun doesn't start shining at the same time every day)