Around the power cables embedded in the walls and through which intense currents circulate a magnetic field is created that can be detected by sensitive devices. By the presence of the magnetic field we can easily locate wires embedded in plastic pipes or other hidden passages.
The detector described is based on an extremely sensitive CMOS integrated circuit which, upon detecting the signals, produces a warning sound on a transducer. The circuit is very simple because in addition to the integrated circuit and the battery we have only three additional passive components of low cost.
The sensitivity of the circuit is due to the very high input impedance of the CMOS integrated circuit. In figure 1 we have the complete diagram of the detector.
The printed circuit board for this assembly is shown in figure 2.
Together with the power supply, which consists of batteries or a 9 V battery, the circuit fits easily into a small plastic box. The sensor consists of a metal plate attached to the bottom of the housing. The piezoelectric transducer can be of any type, even a common microphone cap or piezoelectric tweeter (without the internal transformer).
A sensor probe can also be used, as shown in the figure, operating as a sort of antenna that should be approximated from where it is desired to check whether or not an electric field exists. To use the device, simply pass the sensor to the wall, avoiding direct contact and observe when there is sound from the BZ transducer.
Carefully moving the sensor through the wall can lift the trajectory of the built-in cables according to the sound emission pattern. The capacitor C1 must have a working voltage of 6V or more and S1 is optional since, when the device is out of use, simply remove the batteries or battery.
MATERIAL LIST
Semiconductors:
CI-1 - 4093B - CMOS integrated circuit
Capacitor:
C1 - 10 uF / 6V - electrolytic
Several:
PP - sensor - see text
BZ - piezoelectric transducer - see text
S1 – On/Off switch
B1 - 3, 6 or 9V - batteries or battery
Printed circuit board, battery holder or battery connector, mounting box, wires, solder, etc.
