You saw in project Light Dimmer how a capacitor can store and discharge electricity. You probably noticed that capacitors take a certain amount of time to charge and discharge. Some of you were probably thinking that this fact could be put to some good use in a timer circuit of some sort-and it happens you are right.
Before you finish the wiring, set the select switch up. When you finish the wiring, let the select switch remain at the up position for a few seconds. Then slide it down. The LED comes on for a few seconds and then goes off. Does it stay on longer if you let the select switch remain at the up position for more than a few seconds?
You should have no difficulty in figuring out how this circuit works. You might want to try replacing the 10µF capacitor with a 100µF one and see what happens (be sure to get the + connection right!). What do you think happens now?
You might try adding other capacitors in series and parallel and seeing what effect they have on circuit performance.
Be sure to keep notes of what happens do you see any patterns in the results?