Detection of hidden wiring. Methods for locating underground cables and pipes Searching for electromagnetic radiation from wiring

If the cable line is damaged, this is fraught with economic losses during the transmission of electric current; a short circuit may occur, which will lead to breakdown of powered devices or substations. If the insulating material is damaged, there may be a risk of electric shock.

Searching for damage to cable lines

Damage to the line can cause a disconnection from the power supply of residential buildings, business facilities, management and control systems of workshops and enterprises, and vehicles. Finding violations in the cable line is of primary importance.

What are the types of damage?

Underground and above-ground electrical transmission lines can be damaged for many reasons. The most common situations are:

1. Short circuit of one or more wires to ground;
2. Closing several cores simultaneously to each other;
3. Violation of the integrity of the cores and grounding them as if they were torn;
4. The break lived without grounding;
5. The occurrence of short circuits even with a slight increase in voltage (floating breakdown), which disappear when the voltage normalizes;
6. Violation of the integrity of the insulating material.

To establish the true type of power transmission disturbance, a special device is used - a megohmmeter.

The suspected damaged cable is disconnected from the power sources and the working device. The following indicators are measured at both ends of the wire:

• Phase insulation;
• Linear insulation
• There are no violations of the integrity of the conductors conducting electric current.

Stages of identifying locations of cable line damage

Finding problematic areas in a cable involves three main steps, thanks to which the non-working section can be quickly eliminated:

The first stage is carried out using special equipment. For these purposes, transformers, kenotronomes, or devices capable of generating high frequencies are used. When burning for 20 - 30 seconds, the resistance indicator drops significantly. If there is moisture in the conductor, then the necessary burning procedure takes much longer and the maximum resistance that can be achieved is 2-3 thousand Ohms.

This process takes much longer in the couplings, and the resistance indicators can change in waves, either increasing or falling back. The burning procedure is carried out until a linear decrease in resistance is observed.

The difficulty in determining the location of cable damage is that the length of the cable line can reach several tens of kilometers. Therefore, at the second stage it is necessary to determine the damage zone. To cope with the task, effective techniques are used:

• Method for measuring conductor capacitance;
• Probing pulse technique;
• Creating a loop between the cores;
• Creation of an oscillatory discharge in a conductor.

The choice of technique depends on the expected type of damage.

Capacitive method

Based on the conductor's capacitance, the length from the free end of the conductor to the core break zone is calculated.

Using alternating and direct current, the capacitance of the core that is damaged is measured. The distance is measured based on the fact that the capacitance of a conductor directly depends on its length.

с1/lx = c2/l – lx,

where c1 and c2 are the cable capacitance at both ends, l is the length of the conductor under study, lх is the required distance to the place of the supposed break.

From the presented formula it is not difficult to determine the length of the cable to the break zone, which is equal to:

lх = l * c1/(c1 + c2).

Pulse method

The technique is applicable in almost all cases of conductor damage, with the exception of floating breakdowns caused by high humidity. Since in such cases the resistance in the conductor is over 150 Ohms, which is unacceptable for the pulse method. It is based on applying, using alternating current, a probe pulse to the damaged area and capturing the response signal.

This procedure is carried out using special equipment. Since the pulse transmission speed is constant and amounts to 160 meters per microsecond, it is easy to calculate the distance to the damage zone.

The cable is checked using an IKL-5 or IKL-4 device.

The scanner screen displays pulses of different shapes. Based on the shape, you can roughly determine the type of damage. Also, the pulse method makes it possible to find the place where there is a violation in the transmission of electric current. This method works well if one or more wires are broken, but a bad result is obtained if there is a short circuit.

Loop method

This method uses a special AC bridge to measure changes in resistance. Creating a loop is possible if there is at least one working wire in the cable. If a situation arises where all the cores are broken, you should use the cable cores, which are located in parallel. When a broken core is connected to a working one, a loop is formed on one side of the conductor. A bridge is connected to the opposite side of the cores, which can adjust the resistance.

Finding damage to the power cable using this technique has a number of disadvantages, namely:

• Long preparation and measurement time;
• The measurements obtained are not entirely accurate.
• Short circuits are required.

For these reasons, the method is used extremely rarely.

Oscillatory DISCHARGE method

The method is used if the damage was caused by a floating breakdown. The method involves the use of a kenotron installation, from which voltage is supplied through the damaged core. If a breakdown occurs in the cable during operation, a discharge with a stable oscillation frequency is necessarily formed there.

Considering the fact that the electromagnetic wave has a constant speed, the location of the fault on the line can be easily determined. This can be done by comparing the frequency of oscillations and speed.

Having established the area of ​​damage, an operator is sent to the suspected area to find the point of damage to the power cable. To do this, they use completely different methods, such as:

• Acoustic capture of spark discharge;
• Induction method;
• Rotating frame method.

Acoustic method

This fault detection option is used for underground lines. In this case, the operator needs to create a spark discharge in order to prevent the cable from malfunctioning in the ground. The method works if at the point of damage it is possible to create a resistance of more than 40 ohms. The strength of the sound wave that a spark discharge can create depends on the depth at which the cable is placed, as well as on the structure of the soil.

A kenotron is used as a device capable of generating the required pulse, in the circuit of which it is necessary to additionally include a ball gap and a high-voltage capacitor. An electromagnetic sensor or a piezo sensor is used as an acoustic receiver. Additionally, sound wave amplifiers are used.

Induction method

This is a universal method for searching for all possible types of cable faults; in addition, it allows you to determine the damaged cable line and the depth at which it lies underground. Used to detect couplings connecting cables.

The basis of this method is the ability to detect changes in the electromagnetic field that occur when current moves along an electric line. To do this, a current is passed, which has a frequency of 850 - 1250 Hz. The current strength can be within a few fractions of an ampere up to 25 A.

Knowing how changes in the electromagnetic field under study occur, it will not be difficult to find the location where the integrity of the cable has been compromised. In order to accurately determine the location, you can use cable burning and converting a single-phase circuit into a two- or three-phase one.

In this case, you need to create a core-core circuit. The advantage of such a circuit is that the current is directed in opposite directions (one core forward, the other wire backward). Thus, the field concentration increases significantly and it is much easier to find the location of the damage.

Frame method

This is a good way to find out-of-service areas on the surface of a power line. The principle of operation is very similar to the induction method. The generator is connected to two wires or to one wire and sheath. Then a frame is placed on the damaged cable, which rotates around an axis.

Two signals should clearly appear at the location of the violation - minimum and maximum. Beyond the intended zone, the signal will not fluctuate without producing peaks (monotonic signal).

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There are ways to detect hidden wiring using “folk” methods, without special instruments. For example, you can turn on a large load at the end of this wiring and search by compass deviation or using a coil of wire with a resistance of about 500 Ohms with an open magnetic circuit connected to the microphone input of any amplifier (music center, tape recorder, etc.), turning the volume to maximum. In the latter case, the wire in the wall will be detected by the sound of the 50 Hz pickup.

Device No. 1. It can be used to detect hidden electrical wiring, find a wire break in a bundle or cable, or identify a burnt-out lamp in an electric garland. This is the simplest device consisting of a field-effect transistor, a headphone and batteries. The schematic diagram of the device is shown in Fig. 1. The scheme was developed by V. Ognev from Perm.

Rice. 1. Schematic diagram of a simple finder

The principle of operation of the device is based on the property of the field-effect transistor channel to change its resistance under the influence of interference to the gate output. Transistor VT1 - KP103, KPZOZ with any letter index (in the latter, the housing terminal is connected to the gate terminal). The BF1 phone is a high-resistance phone, with a resistance of 1600-2200 Ohms. The polarity of connecting the GB1 battery does not matter.

When searching for hidden wiring, the housing of the transistor is moved along the wall and the maximum volume of sound with a frequency of 50 Hz (if it is electrical wiring) or radio transmissions (radio broadcast network) is used to determine the location of the wires.

The location of a broken wire in an unshielded cable (for example, the power cord of any electrical or radio device), or a burnt-out lamp of an electric garland is found in this way. All wires, including the broken one, are grounded, the other end of the broken wire is connected through a resistor with a resistance of 1-2 MOhm to the phase wire of the electrical network and, starting with the resistor, move the transistor along the bundle (garland) until the sound stops - this is the place where the wire breaks or a faulty lamp.

The indicator can be not only a headset, but also an ohmmeter (shown as dashed lines) or an avometer included in this operating mode. Power supply GB1 and telephone BF1 are not needed in this case.

Device No. 2. Now consider a device made with three transistors (see Fig. 2). A multivibrator is assembled on two bipolar transistors (VT1, VT3), and an electronic switch is assembled on a field-effect transistor (VT2).

Rice. 2. Schematic diagram of a three-transistor finder

The principle of operation of this finder, developed by A. Borisov, is based on the fact that an electric field is formed around an electric wire - this is what the finder picks up. If the SB1 switch button is pressed, but there is no electric field in the area of ​​the WA1 antenna probe, or the finder is located far from the network wires, the VT2 transistor is open, the multivibrator does not work, and the HL1 LED is off.

It is enough to bring the antenna probe connected to the gate circuit of the field-effect transistor closer to the conductor with current or simply to the network wire, transistor VT2 will close, the shunting of the base circuit of transistor VT3 will stop and the multivibrator will start working.

The LED will start flashing. By moving the antenna probe near the wall, it is easy to trace the route of network wires in it.

The field-effect transistor can be any other from the series indicated in the diagram, and bipolar transistors can be any from the KT312, KT315 series. All resistors - MLT-0.125, oxide capacitors - K50-16 or other small ones, LED - any of the AL307 series, power source - Corundum battery or 6-9 V battery, push-button switch SB1 - KM-1 or similar.

The body of the finder can be a plastic pencil case for storing school counting sticks. The board is mounted in its upper compartment, and the battery is placed in the lower compartment.

You can regulate the oscillation frequency of the multivibrator, and therefore the frequency of LED flashes, by selecting resistors R3, R5, or capacitors CI, C2. To do this, you need to temporarily disconnect the source output of the field-effect transistor from resistors R3 and R4 and close the switch contacts.

Device No. 3. The finder can also be assembled using a generator using bipolar transistors of different structures (Fig. 3). The field-effect transistor (VT2) still controls the operation of the generator when the antenna probe WA1 enters the electric field of the network wire. The antenna must be made of wire 80-100 mm long.

Rice. 3. Schematic diagram of a finder with a generator on

Transistors of various structures

Device No. 4. This device for detecting damage to hidden electrical wiring is powered from an autonomous source with a voltage of 9 V. The circuit diagram of the finder is shown in Fig. 4.

Rice. 4. Schematic diagram of a finder with five transistors

The principle of operation is as follows: one of the wires of the hidden electrical wiring is supplied with an alternating voltage of 12 V from a step-down transformer. The remaining wires are grounded. The finder turns on and moves parallel to the wall surface at a distance of 5-40 mm. In places where the wire is broken or terminated, the LED goes out. The finder can also be used to detect core faults in flexible cables and hose cables.

Device No. 5. Hidden wiring detector, shown in Fig. 5, already made on the K561LA7 chip. The scheme is presented by G. Zhidovkin.

Fig.5. Schematic diagram of a hidden wiring finder on the K561LA7 chip

Note.

Resistor R1 is needed to protect it from increased voltage of static electricity, but, as practice has shown, it does not need to be installed.

The antenna is a piece of ordinary copper wire of any thickness. The main thing is that it does not bend under its own weight, that is, it is rigid enough. The length of the antenna determines the sensitivity of the device. The most optimal value is 5-15 cm.

This device is very convenient for determining the location of a burnt-out lamp in a Christmas tree garland - the crackling noise stops near it. And when the antenna approaches the electrical wiring, the detector emits a characteristic crackling sound.

Device No. 6. In Fig. 6 shows a more complex finder, which, in addition to sound, also has a light indication. The resistance of resistor R1 must be at least 50 MOhm.

Rice. 6. Schematic diagram of a finder with sound and light indication

Device No. 7. Finder, the diagram of which is shown in Fig. 7, consists of two nodes:

♦ an AC voltage amplifier, based on the micropower operational amplifier DA1;

♦ an audio frequency oscillation generator assembled on an inverting Schmitt trigger DD1.1 of the K561TL1 microcircuit, a frequency-setting circuit R7C2 and a piezo emitter BF1.

Rice. 7. Schematic diagram of the finder on the K561TL1 chip

The principle of operation of the finder is as follows. When the WA1 antenna is located close to the current-carrying wire of the power supply network, the EMF pickup at a frequency of 50 Hz is amplified by the DA1 microcircuit, as a result of which the HL1 LED lights up. This same op-amp output voltage, pulsating at 50 Hz, drives the audio frequency oscillator.

The current consumed by the device microcircuits when powered from a 9 V source does not exceed 2 mA, and when the HL1 LED is turned on, it is 6-7 mA.

When the required electrical wiring is located high, it is difficult to observe the glow of the HL1 indicator and an audible alarm is sufficient. In this case, the LED can be turned off, which will increase the efficiency of the device. All fixed resistors are MLT-0.125, adjusted resistor R2 is SPZ-E8B type, capacitor CI is K50-6.

Note.

For a smoother adjustment of sensitivity, the resistance of resistor R2 should be reduced to 22 kOhm, and its lower terminal in the diagram should be connected to the common wire through a resistor with a resistance of 200 kOhm.

The WA1 antenna is a foil pad on a board measuring approximately 55x12 mm. The initial sensitivity of the device is set by trimming resistor R2. The faultlessly installed device, developed by S. Stakhov (Kazan), does not need adjustment.

Device No. 8. This universal indicator device combines two indicators, allowing you not only to identify hidden wiring, but also to detect any metal object located in the wall or floor (fittings, old wires, etc.). The finder circuit is shown in Fig. 8.

Rice. 8. Schematic diagram of a universal finder

The hidden wiring indicator is based on the DA2 micropower operational amplifier. When a wire connected to the input of the amplifier is located near the electrical wiring, a pickup frequency of 50 Hz is perceived by the WA2 antenna, amplified by a sensitive amplifier assembled on DA2, and switches the HL2 LED with this frequency.

The device consists of two independent devices:

♦ metal detector;

♦ hidden electrical wiring indicator.

Let's look at the operation of the device according to its schematic diagram. An RF generator is assembled on transistor VT1, which is put into excitation mode by adjusting the voltage based on VT1 using potentiometer R6. The RF voltage is rectified by the diode VD1 and moves the comparator assembled on the DA1 op-amp to a position in which the HL1 LED goes out and the periodic sound signal generator assembled on the DA1 chip is turned off.

By rotating the sensitivity regulator R6, the operating mode of VT1 is set at the generation threshold, which is controlled by turning off the HL1 LED and the periodic signal generator. When a metal object enters the inductance field L1/L2, the generation is interrupted, the comparator switches to a position in which the HL1 LED lights up. A periodic voltage with a frequency of about 1000 Hz with a period of about 0.2 s is applied to the piezoceramic emitter.

Resistor R2 is designed to set the lasing threshold mode at the middle position of potentiometer R6.

Advice.

The receiving antennas WA 7 and WA2 should be as far away from hand as possible and located in the head of the device. The part of the housing in which the antennas are located should not have an internal foil coating.

Device No. 9. Small-sized metal detector. A small-sized metal detector can detect nails, screws, and metal fittings hidden in walls at a distance of several centimeters.

Operating principle. The metal detector uses a traditional detection method based on the operation of two generators, the frequency of one of which changes as the device approaches a metal object. A distinctive feature of the design is the absence of homemade winding parts. The winding of an electromagnetic relay is used as an inductor.

The schematic diagram of the device is shown in Fig. 9, a.

Rice. 9. Small-sized metal detector: a - circuit diagram;

b - printed circuit board

The metal detector contains:

♦ LC generator on element DDL 1;

♦ RC generator based on elements DD2.1 and DD2.2;

♦ buffer stage on DD 1.2;

♦ mixer on DDI.3;

♦ voltage comparator on DD1.4, DD2.3;

♦ output stage on DD2.4.

The device works like this. The frequency of the RC oscillator must be set close to the frequency of the LC oscillator. In this case, the output of the mixer will contain signals not only with the frequencies of both generators, but also with the difference frequency.

The R3C3 low-pass filter selects difference frequency signals that are fed to the input of the comparator. At its output, rectangular pulses of the same frequency are formed.

From the output of element DD2.4 they are supplied through capacitor C5 to connector XS1, into the socket of which a headphone plug with a resistance of about 100 Ohms is inserted.

The capacitor and the telephones form a differentiating chain, so clicks will be heard in the telephones with the appearance of each rising and falling pulse, i.e., with double the signal frequency. By changing the frequency of clicks, you can judge the appearance of metal objects near the device.

Element base. Instead of those indicated in the diagram, it is permissible to use the following microcircuits: K561LA7; K564LA7; K564LE5.

Polar capacitor - series K52, K53, others - K10-17, KLS. Variable resistor R1 - SP4, SPO, constant - MLT, S2-33. Connector - with contacts that close when the telephone plug is inserted into the socket.

The power source is a Krona, Corundum, Nika battery or a similar battery.

Preparing the coil. Coil L1 can be taken, for example, from an electromagnetic relay RES9, passport RS4.524.200 or RS4.524.201 with a winding resistance of about 500 Ohms. To do this, the relay needs to be disassembled and the moving elements with contacts removed.

Note.

The relay magnetic system contains two coils wound on separate magnetic circuits and connected in series.

The common terminals of the coils must be connected to capacitor C1, and the magnetic circuit, as well as the housing of the variable resistor, to the common wire of the metal detector.

Printed circuit board. The device parts, except for the connector, should be placed on a printed circuit board (Fig. 9, 6) made of double-sided fiberglass foil. One of its sides should be left metallized and connected to the common wire of the other side.

On the metallized side you need to attach the battery and the coil “extracted” from the relay.

The relay coil leads should be passed through the countersunk holes and connected to the corresponding printed conductors. The remaining parts are placed on the printing side.

Place the board in a case made of plastic or hard cardboard, and secure the connector to one of the walls.

Setting up a metal detector. Setting up the device should begin by setting the frequency of the LC generator within the range of 60-90 kHz by selecting capacitor C1.

Then you need to move the variable resistor slider to approximately the middle position and select capacitor C2 to make a sound signal appear in the phones. When moving the resistor slider in one direction or another, the frequency of the signal should change.

Note.

To detect metal objects with a variable resistor, you must first set the sound signal frequency as low as possible.

As you approach the object, the frequency will begin to change. Depending on the setting, above or below zero beats (equality of generator frequencies), or the type of metal, the frequency will change up or down.

Device No. 10. Indicator of metal objects.

When carrying out construction and repair work, it will be useful to have information about the presence and location of various metal objects (nails, pipes, fittings) in the wall, floor, etc. The device described in this section will help with this.

Detection parameters:

♦ large metal objects - 10 cm;

♦ pipe with a diameter of 15 mm - 8 cm;

♦ screw M5 x 25 - 4 cm;

♦ nut M5 - 3 cm;

♦ screw M2.5 x 10 -1.5 cm.

The operating principle of the metal detector is based on the property of metal objects to introduce attenuation into the frequency-setting LC circuit of a self-oscillator. The self-oscillator mode is set near the generation failure point, and the approach of metal objects (primarily ferromagnetic) to its contour significantly reduces the amplitude of oscillations or leads to generation failure.

If you indicate the presence or absence of generation, you can determine the location of these objects.

The schematic diagram of the device is shown in Fig. 10, a. It has sound and light indication of the detected object. An RF self-oscillator with inductive coupling is assembled on transistor VT1. The frequency-setting circuit L1C1 determines the generation frequency (about 100 kHz), and the coupling coil L2 provides the necessary conditions for self-excitation. Resistors R1 (RUB) and R2 (SOFT) can set the operating modes of the generator.

Fig. 10. Metal object indicator:

A - schematic diagram; b - design of the inductor;

B - printed circuit board and placement of elements

A source follower is assembled on transistor VT2, a rectifier is assembled on diodes VD1, VD2, a current amplifier is assembled on transistors VT3, VT5, and a sound alarm is assembled on transistor VT4 and piezo emitter BF1.

In the absence of generation, the current flowing through resistor R4 opens transistors VT3 and VT5, so LED HL1 will light and the piezo emitter will emit a tone at the resonant frequency of the piezo emitter (2-3 kHz).

If the RF self-oscillator is working, then its signal from the output of the source follower is rectified, and the negative voltage from the rectifier output will close transistors VT3, VT5. The LED will go out and the jamming alarm will stop sounding.

When the circuit approaches a metal object, the amplitude of vibrations in it will decrease, or the generation will fail. In this case, the negative voltage at the detector output will decrease and current will begin to flow through transistors VT3, VT5.

The LED will light up and a beep will sound, indicating the presence of a metal object near the circuit.

Note.

With an audible alarm, the sensitivity of the device is higher, since it starts working at a current of a fraction of a milliampere, while a LED requires much more current.

Element base and recommended replacements. Instead of those indicated in the diagram, the device can use transistors KPZOSA (VT1), KPZZV, KPZZG, KPZOSE (VT2), KT315B, KT315D, KT312B, KT312V (VT3 - VT5) with a current transfer coefficient of at least 50.

LED - any with an operating current of up to 20 mA, diodes VD1, VD2 - any of the KD503, KD522 series.

Capacitors - KLS, K10-17 series, variable resistor - SP4, SPO, tuning - SPZ-19, constant - MLT, S2-33, R1-4.

The device is powered by a battery with a total voltage of 9 V. The current consumption is 3-4 mA when the LED is not lit and increases to approximately 20 mA when it is lit.

If the device is not used often, then switch SA1 can be omitted, supplying voltage to the device by connecting the battery.

Design of inductors. The design of the inductor coil of the self-oscillator is shown in Fig. 10, b - it is similar to the magnetic antenna of a radio receiver. Paper sleeves 2 (2-3 layers of thick paper) are put on a round rod 1 made of ferrite with a diameter of 8-10 mm and a permeability of 400-600; coils L1 (60 turns) and L2 ( 20 turns) - 3.

Note.

In this case, winding must be carried out in one direction and the terminals of the coils must be correctly connected to the self-oscillator

In addition, coil L2 should move along the rod with little friction. The winding on the paper sleeve can be secured with tape.

Printed circuit board. Most of the parts are placed on a printed circuit board (Fig. 10, c) made of double-sided foil fiberglass. The second side is left metallized and is used as a common wire.

The piezo emitter is located on the back side of the board, but it must be isolated from metallization using electrical tape or tape.

The board and battery should be placed in a plastic case, and the coil should be installed as close to the side wall as possible.

Advice.

To increase the sensitivity of the device, the board and battery must be placed at a distance of several centimeters from the coil.

Maximum sensitivity will be on the side of the rod on which coil L1 is wound. It is more convenient to detect small metal objects from the end of the coil; this will allow you to more accurately determine their location.

♦ step 1 - select resistor R4 (to do this, temporarily unsolder one of the terminals of the diode VD2 and install resistor R4 of such a maximum possible resistance so that there is a voltage of 0.8-1 V at the collector of transistor VT5, while the LED should light up and the sound signal should sound.

♦ step 2 - set the resistor R3 slider to the bottom position according to the diagram and solder the VD2 diode, and unsolder the L2 coil, after which the transistors VT3, VT5 should close (the LED will go out);

♦ step 3 - carefully moving the slider of resistor R3 up the circuit, ensure that transistors VT3, VT5 open and the alarm turns on;

♦ step 4 - set the sliders of resistors Rl, R2 to the middle position and solder coil L2.

Note.

When L2 approaches close to L1, generation should occur and the alarm should turn off.

♦ step 5 - remove coil L2 from L1 and achieve the moment the generation fails, and use resistor R1 to restore it.

Advice.

When tuning, you should strive to ensure that coil L2 is removed to the maximum distance, and resistor R2 can be used to disrupt and restore generation.

♦ step 6 - set the generator to the brink of failure and check the sensitivity of the device.

At this point, setting up the metal detector is considered complete.

When you plan to hang a picture or wall clock, how do you choose the right place? You are probably thinking about how the painting will fit into the interior of the room, which wall is best to place it on and how. But have you ever thought that not everywhere you can hammer a nail into the wall and drill a hole for a dowel? It's not about what material your walls are made of, since there is a more significant circumstance - this is the electrical wiring. In order not to damage the wires walled up in the wall, you need to know where they are laid.

There are several ways to find out approximately where the electrical cable runs: you should look at the technical documentation of the apartment and look at the wiring diagram of the electrical network; if there is none, then pay attention to the location of the branch boxes, from which the wires go to sockets and switches. As a rule, smart electricians lay the cable at a right angle.

It’s good when you replaced the old electrical wiring and are aware of its placement, but what if the previous owner of the house was a self-taught electrician and did not follow the basic rules of wiring? There are cases when, in order to save money, the wires are routed along the shortest path: from the boxes diagonally and horizontally - in this case, you cannot do without special means for detecting it.

In stores and radio markets they sell special devices called “Hidden Wiring Detector”. They are cheap (low class) and expensive (high class). A low-class device detects the source of electromagnetic radiation - these are live wires and electrical appliances. High-class detectors are more accurate and functional: their work is aimed at identifying wires directly, even those that are without voltage.

For home use, a simple detector that you can make yourself will be enough for us. As you understand, the simple circuit we have assembled refers to budget devices - therefore, we will not be able to create a high-end device. But a homemade product will help you avoid getting into trouble when performing construction work and at the moment when you decide to decorate your room with a beautiful painting or wall clock. In order to quickly assemble a hidden wiring detector ourselves, we will need three non-scarce radio components, which will not be difficult for us to find.

The main element is the Soviet K561LA7 microcircuit (the detector itself is assembled on it). The microcircuit is sensitive to electromagnetic and static fields emanating from conductors of electrical energy and electronic devices. The microcircuit is protected from increased electrostatic fields by a resistor, which is an intermediate element between the antenna and the IC. The sensitivity of the detector is determined by the length of the antenna. As an antenna, you can use a single-core copper wire 5 to 15 centimeters long. For stable operation and without compromising sensitivity, I chose a length of 8 centimeters. There is one caveat: if the antenna length exceeds the threshold of 10 centimeters, there is a risk of the microcircuit going into self-excitation mode. In this case, the detector may not work correctly. Also, if the electrical cable is buried deep in the plaster, the detector may not make a single sound.

If your homemade detector does not work correctly, you should experiment with a long copper antenna. It can be either shorter or longer than the recommended length. When the detector stops responding to anything except the electrical cable, then you have found the desired length (if you have chosen the wrong length, the detector may respond to a simple touch from a person or any objects).

We have sorted out the nuances, now we move on to the third element of the circuit - this is the piezoelectric element. A piezo emitter (piezoelement) is necessary for auditory perception of the electromagnetic field; when this happens, the emitter makes a crackling sound. A piezoelectric element, or simply a “squeaker,” can be obtained from a non-working Tetris, Tamagotchi or watch. You can also replace the tweeter with a milliammeter from an old tape recorder. The milliammeter will show the level of the emitted field by deflecting the needle. If you decide to use a piezoelectric element and a milliammeter, the crackling noise produced will be a little quieter.

The circuit is powered by a voltage of 9 volts, so we will need a Krona battery. The circuit can be assembled on a printed circuit board or mounted. Wall-mounted installation for a simple circuit consisting of 5 elements would be preferable. Take cardboard, place the microcircuit with the legs down and pierce holes under each leg with a needle (14 pieces, 7 on each side). After preparing the place for the microcircuit, insert the legs into the holes made and bend them. This way we will securely fix the integrated circuit on the cardboard and make the work easier when soldering wires.

To avoid overheating the microcircuit, you should use a low-power soldering iron. Usually a 25 Watt soldering iron is used for soldering radio components. Let's start assembling the detector according to the diagram given in the article. If you have followed all the above recommendations, then the circuit should work instantly without any adjustments. Now we find a suitable case and integrate the circuit into it. Make holes under the tweeter and glue the piezo emitter on the back side. To prevent the detector from working constantly, solder a toggle switch into the power supply circuit break. Rebooting the detector by turning the toggle switch on and off will help you remove the microcircuit from self-excitation mode.

By tradition, I would like to end the article with a video report on the work done. The video tested the operation of a homemade and factory-made hidden wiring detector. As it turned out, the made detector more accurately showed the location of the electrical cable than a cheap commercial detector.

Having assembled a detector to search for hidden wiring, you should not be afraid of damage to the electrical network of your home, because you will always be able to find the electrical cable. Good luck in mastering simple circuits in radio electronics. If you have any questions, please contact me in the comments - we’ll sort it out!

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Greetings, dear readers! My name is Max. I am convinced that almost everything can be done at home with your own hands, I am sure that everyone can do it! In my free time I like to tinker and create something new for myself and my loved ones. You will learn about this and much more in my articles!

The device is designed to search for alternating current electrical networks underground and in the channels of concrete and brick buildings, their location and depth.

Before searching for the route, an audio frequency voltage of sufficient power should be applied to disconnected cable lines, and the end of the line should be temporarily closed; this should also be done in the event of possible mechanical damage; the electromagnetic field in the damaged area is always several times higher than in a healthy section of the line.

The principle of operation of the device is based on the conversion of the electromagnetic field of the electrical network with a frequency of 50 Hz into an electrical signal, the level of which depends on the voltage and current in the conductor, as well as on the distance to the radiation source and the shielding factors of soil or concrete.

The device circuit consists of an electromagnetic field sensor BF1, a pre-amplifier on a transistor VT1, a power amplifier DA1 and an output control device consisting of a sound analyzer on headphones BA1, a light peak indicator HL1 and a galvanic power indicating device - PA1. To reduce distortion of the electromagnetic field signal, negative feedback circuits are introduced into the amplifier circuits. The use of a powerful low-frequency amplifier at the output allows you to connect a load of any resistance and power.

Installation resistors and regulators are introduced into the circuit to optimize the operating mode of the device circuit. The device can estimate the depth of the electrical network from the surface of the earth.

To power the device circuit, a current source of the Krona type at 9 volts or a KBS at a voltage of 2 * 4.5 volts is sufficient.

To eliminate accidental discharge of batteries, the circuit uses double shutdown: by opening the positive power bus of the power bus when the BA1 headphones are turned off.

The BF1 electromagnetic sensor is used from high-impedance telephone headphones of the TON-1 type with the metal membrane removed. It is connected to the pre-amplifier on transistor VT1 through the coupling capacitor C2. Capacitor C3 reduces the level of high-frequency interference, especially radio interference. The amplifier on transistor VT1 has voltage feedback from the collector to the base through resistor R1; when the voltage on the collector increases, the voltage on the base increases, the transistor opens and the collector voltage decreases. Power is supplied to the amplifier through load resistor R2 from filter C1, R4. Resistor R3 in the emitter circuit of transistor VT1 mixes the characteristics of the transistor and, due to the negative voltage level, slightly reduces the gain at signal peaks. The pre-amplified electromagnetic field signal is supplied through galvanic isolation capacitor C4 to the gain regulator R5 and then through resistor R6 and capacitor C6 to input (1) of the analog power amplifier chip DA1. Capacitor C5 reduces frequencies above 8000 Hz for better signal perception.

The audio power amplifier on the DA1 chip with an internal device for protecting against short circuits in the load and overload allows you to amplify the input signal with good parameters to a value sufficient to operate a load of up to 1 watt.

The distortion in the signal introduced by the amplifier during operation depends on the value of the negative feedback. The OS circuit consists of resistors R7, R8 and capacitor C7. With resistor R7 it is possible to adjust the feedback coefficient based on the quality of the signal.
Capacitor C9 and resistor R8 eliminate self-excitation of the microcircuit at low frequencies.

Through the isolation capacitor C10, the amplified signal is supplied to the load BA1, the level indicator PA1 and the LED indicator HL1.
Electrodynamic headphones are connected to the output of the amplifier via connector XS1 and XS2, the jumper in XS1 closes the power supply circuit from battery GB1 to the circuit. The HL1 indicator light monitors the presence of output signal overload.

Galvanic device PA1 indicates the signal level depending on the depth of the electrical network and is connected to the output of the amplifier through an isolation capacitor C11 and a voltage multiplier on diodes VD1-VD2.

There are no scarce radio components in the power grid search device: the BF1 electromagnetic field receiver can be made from a small-sized matching transformer or an electromagnetic coil.
Resistors type C1-4 or MLT 0.12, capacitors type KM, K53.
Reverse conduction transistor KT 315 or KT312B. Pulse diodes for current up to 300 mA.
A foreign analogue of the DA1 chip is TDA2003.
The PA1 level device is used from the recording level indicator of tape recorders with a current of up to 100 μA.
HL1 LED of any type. Headphones BA1 - TON-2 or small-sized ones from players.

A correctly assembled device begins to work immediately, by placing the electromagnetic field sensor on the power cord of the switched-on soldering iron, set resistor R7 to the maximum volume of the signal in the headphones, when
middle position of the R5 “Gain” regulator.

All radio components of the circuit are located on the printed circuit board except for the BF1 sensor, which is installed in a separate metal box. The power battery - KBS is fixed outside the case with a bracket. All housings with radio components are mounted on an aluminum rod.

You can start testing the power grid search device without leaving your home; just turn on the light of one of the lamps and clarify the route in the wall and ceiling from the switch to the lamp, and then proceed to search for routes underground in the courtyard of the house.

Literature:
1. I. Semenov Measurement of high currents. "Radiomir" No. 7 / 2006 p. 32
2. Yu.A. Myachin 180 analog microcircuits. 1993
3. V.V. Mukoseev and I.N. Sidorov Marking and designation of radioelements. Directory. 2001
4. V. Konovalov. Device for searching electrical wires - Radio, 2007, No. 5, S41.
5. V. Konovalov. A. Vanteev Search for underground power networks, Radiomir No. 11, 2010, C16.

The importance of accurate information.

Information about the location and actual condition of underground pipelines and cable lines is the most important result of the survey of these communications.

The reliability and accuracy of survey results are the only characteristics that can be of real value. Inaccurate or distorted information can cause errors in the interpretation of the data obtained and cause unnecessary costs. It is even worse if people's lives and health are endangered as a result of incomplete or inaccurate survey data.

The final conclusion about the condition of an object or its individual element can be made on the basis of its visual inspection, however, this seems impossible for underground cables and pipes. Experience, knowledge of the work area being inspected, the use of drawings or diagrams, as well as the effective use of route finders can provide information that will make it possible to give an almost accurate conclusion about the condition of the elements of the object. In some cases, there may be areas where it is impossible to accurately determine the status of communications. These areas should always be localized to allow further investigation.

Locating underground pipelines and cables is a very responsible activity: all operations must be carried out methodically, accurately and with great attention. In this series of articles, I will try to provide structured and, if possible, complete information about the methods of using route finders to obtain accurate and reliable data.

Methods for locating underground cables and pipes

Currently, the most widespread methods for detecting and tracing underground cables and pipelines are:

1 Available documentation

Diagrams and drawings available from utility companies or city administration contain a wealth of information about the presence and position of underground pipes and cables. When conducting a site survey, it is first important to obtain any available information and available documentation. The information may be (and usually is) inaccurate or incomplete, but this information will provide the operator with a starting point when performing a site survey. In addition, it is much easier to confirm or supplement existing information than to start surveying the area “blindly.” Before work begins on site, any information can be very useful, even if it only gives an idea of ​​what to expect at the site.

Ground penetrating radar is a radar that, unlike the classic one, is used to probe the environment under study, rather than the airspace. The environment being studied can be land (hence the most common name - ground penetrating radar), water, building walls, etc.

Modern georadar is a complex geophysical device created using certain technologies. The main unit consists of electronic components that perform the following functions: generating pulses emitted by the transmitting antenna, processing signals coming from the receiving antenna, synchronizing the operation of the entire system. Thus, the georadar consists of three main parts: the antenna part, the recording unit and the control unit. The antenna part includes transmitting and receiving antennas. The recording unit is understood as a laptop or other recording device, and the role of the control unit is performed by a system of cables and optical-electrical converters (according to Wikipedia).

GPR

Methods for searching underground communications, based on the use of electromagnetic waves, have been developed to accurately detect, determine the dimensions and distance (depth) to underground objects. The location of underground communications, in particular plastic pipelines or fiber-optic communication cables, has become a reasonable and natural development of this method. Obviously, using radar it is quite difficult (in most cases, almost impossible) to distinguish plastic pipes with water from dense soil (for example, wet clay and earth). However, ground penetrating radars provide an approximate picture of the location of underground cables and pipes in various types of soil. At the same time, even in favorable conditions for the use of radars, it is necessary to have an appropriate understanding of what is or should be underground.

The high conductivity of fine-grained sedimentary rocks - clays and sediments - sharply reduces the capabilities of the device, and rocky and heterogeneous sedimentary rocks scatter its signal. High groundwater levels can also negatively affect survey results. It is also worth noting that the information obtained from the results of GPR operation is very complex and requires interpretation by a highly qualified specialist with extensive experience. Complexity, high cost and dependence on application conditions make it inappropriate to use this method for daily work. However, it is likely that in the very near future this method will become useful in drawing up underground utility diagrams.

Acoustic methods are most widely used when searching for water leaks in underground pipelines. However, a variation of this method has become quite widespread for routing underground water pipes, especially plastic pipelines. Currently, the use of this method is limited to the detection and location of water pipes, however, further development of such methods can expand the scope of their application, in particular, for use in tracing underground plastic gas pipes.

The temperature of underground cables and pipes may be different from the temperature of the surrounding soil. Determining this temperature difference can be a fairly effective method for locating underground pipes and cables. However, the effectiveness of this method is highly dependent on environmental conditions and is significantly reduced by factors such as sunlight or wind. In practice, these methods have a highly specialized application - searching for voids in sewer collectors, as well as locating breaks, cracks and places of damage to the insulating coating in certain sections of heating mains.

This is the oldest method of searching for water and underground pipelines. To search with dowsers, a tree branch or vine is used, as well as its numerous variants in the form of welding electrodes, etc. This interesting method requires specific skills and intuition. I personally have repeatedly observed the work of such “craftsmen” and I can say that the results of their work impressed me. One day, a specialist from one of the Vodokanals walked along the route of a power cable with two electrodes, showing the direction of the cable and coupling. The length of the route was about 130 meters, the cable often changed its direction, parallel examination using an electromagnetic locator completely confirmed the results obtained using electrodes. Of course, it is difficult to expect widespread use of this method, and the advantages include the low cost and light weight of the equipment;-)

This is a universal and most common method of locating and tracing underground communications. The advantage of this method is the ability to obtain “from underground” a large amount of information that cannot be obtained using any other technology. This method has the following distinctive features:

Searching for the boundaries of underground cables and pipes from the surface of the earth;
- Tracing and identification of certain lines;
- Tracing and identification of sewers or other non-metallic channels and pipes to which there is access; localization of blockages and damage (using a miniature pushable transmitter “probe”);
- Measurement of burial depth (distance from the soil surface to the center of the electromagnetic field around the communication) directly from the surface of the earth;
- Portability and light weight of the equipment (easily held in the hands) and the ability to be used effectively even by inexperienced operators;
- Possibility of using route finders with any type of soil and even under water;