Contactless AC Mains Voltage Detector

 This is a CMOS IC (CD4033) based circuit which can be used to detect presence of mains AC voltage without
 any electrical contact with the conductor carrying AC current/voltage. Thus it can be used to detect mains AC
 voltage without removing the insulation from the conductor. Just take it in the vicinity of the conductor and it
 would detect presence of AC voltage. If AC voltage is not present, the display would randomly show any digit
 (0 through 9) permanently. If mains supply is available in the conductor, the electric field would be induced into
 the sensing probe. Since IC used is CMOS type, its input impedance is extremely high and thus the induced
 voltage is sufficient to clock the counter IC. Thus display count advances rapidly from 0 to 9 and then repeats
 itself. This is the indication for presence of mains supply. Display stops advancing when the unit is taken away
 from the mains carrying conductor. For compactness, a 9-volt PP