With a single IC you can make a simple Non Contact AC tester. Just move in front of an AC wire, switch board etc that carrying AC, the LEDs in the circuit runs indicating the presence of AC in the wire.
IC CD 4017 is the Johnson Decade Counter with 10 outputs. Its input pin 14 receives pulses and accordingly, its outputs go high one by one. Here the 50 Hz AC hum present around the live wire acts as the pulses for the input of IC. So by receiving the pulses IC gives high out puts one by one and LED lights. It can detect the AC from a distance of 1 foot.Use 10 cm plastic wire as antenna.
Caution: Do not make the Antenna in contact with live points of AC switch board or Sockets. It can give fatal shock.