You can demonstrate the Piezoelectricity using this two component circuit. Just connect a high bright transparent LED to the Piezo element and gently tap on it. You can see the LED flashing without a battery power. Try and make a Fun.
Use this Automatic White LED Lamp in the Child’s study room to avoid the panic situation of a sudden power failure. It gives sufficient light to move away from the room. Make it and impress the child.If it is enclosed in Doll with White LED as the head light, the child will be happy.
Make this Tiny Locker guard and Thwart the attempt of Burglary. This tiny circuit beeps when the door of Locker or Almirah opens in daytime. It beeps a few minutes after the light enters into the locker as a trick to confuse the burglar. It uses LDR as the light sensor.
Make this simple Electronic Mail Box and impress your friends. It gives beeps when a letter is placed in the letter box and intimates the arrival of Mail. The circuit is too simple and uses an LDR as dark sensor and White LED as illuminator.