I have a project for school and could use some advice on where to start - I must build or develop device that will operate for exactly 14 sec after being started. At the end of 14 sec, the device must either turn on a small light bulb or ring a bell. After the initial run, I will have to change the time interval by plus or minus 3 seconds. What's allowed: homemade electrical devices stored potential energy in form of springs, rubber bands gravitational potential energy batteries for lighting bulb or ringing bell windup toys not initially designed for specific time intervals pendulums of our own design What's not allowed: commercial electronic timing devices commercial clocks any 110volt operated devices any device that will not sit on top of tables no chemical reactions any device that has no circuitry used to light bulb/ring bell I have no problem creating a circuit to light a light bulb, but wondering on how to achieve time delay without timing device. Thoughts??? Thank you!