Detector circuit for detecting hidden wiring. DIY hidden wiring detector, manufacturing diagram and design options. Sound and light indication

Sometimes the problem of finding hidden wiring during an apartment renovation becomes a real pain. To avoid this, it is necessary to have a hidden wall wiring detector in your home tool kit. Such devices are available for free sale, but if you like to create home-made devices and do not want to spend money on buying a factory product, you can assemble a device that will help you find out, if necessary, where the walled-up wiring is located yourself. From this material you will learn what a hidden wiring detector is, what types of these devices exist, and how you can make such a detector with your own hands.

Types of wiring finders

There are four types of these devices, differing from each other in their operating principles. Each of them detects hidden electrical wiring in the wall according to various physical parameters, and they are called accordingly:

Electrostatic. Their work is based on searching for the electric field that is created by voltage. This design is the simplest and can be easily done at home.
Electromagnetic. Such devices detect the magnetic field that is created by the flow of electrons in the wiring.

Inductive metal detectors. These devices create an electromagnetic field themselves, and by the changes that occur in it, they detect the metal of de-energized cables.
Combined factory instruments. These are the best, most sensitive and accurate devices used for professional work, but their price, compared to other types of wiring detectors, is the highest.

A detector for hidden wiring in the wall is often built into the circuit of multifunctional devices intended for servicing electrical networks. The most famous of them is "Woodpecker". This device combines several useful devices at the same time.

Types of devices for searching hidden wiring and testing them on video:

How to find electrical wiring in walls using a voltage indicator?

The easiest way to determine where hidden wiring is is to use an improved voltage indicator (sonic screwdriver). This device is self-powered; in addition, it contains a sound annunciator and a signal amplification device.

If you have such a tool, then you do not need to make a hidden wiring indicator yourself or make any changes to the device circuit. It is not difficult to detect hidden electrical wiring with its help.

Simply run the tip of this screwdriver, with your finger against it, along the wall. The instrument will respond to electromagnetic pulses emitted by electrical wiring and notify you with a sound about the location where they are present.

Assembling a wiring finder with a field-effect transistor

The easiest way is to assemble a hidden wiring detector yourself, the circuit of which contains a field-effect transistor. The operating principle of this device is based on recording an electric field.

To assemble such a determinant, you do not need to be a professional; it is enough to have minimal electrical knowledge.

This circuit connects the following elements:

Field effect transistor (KP103, KP303).
A speaker with a resistance value of 1.6-2.2 kOhm. A part from a landline telephone will do.
Battery (1.5-9 V).
Switch.
Connecting cables.

The circuit is assembled using the soldering method. As a housing for the mounted device, you can use a simple plastic container of small volume.

The video shows an example of assembling a homemade wiring finder:

It must be taken into account that the field-effect transistor is easily subject to electrostatic breakdown. Therefore, when connecting it to the circuit, you should not touch the terminals with your fingers.

In addition, the tweezers and soldering iron must be grounded.

Detector with field-effect transistor: operating procedure

The device operates according to the following principle. An electric field acting on an n-p junction leads to a change in the thickness of the latter, as a result of which its conductivity also changes. Since the change in the electric field coincides with the network frequency (50 Hz), when approaching the wiring, an increasing hum will be heard from the speaker. In order not to confuse the terminals of the field-effect transistor, it is necessary to check their markings.

It is desirable that the transistor body be metal, connected to a gate, which serves as the control output in this circuit. The housing part will play the role of a receiving antenna, capturing the signal emitted by the wiring.

Using this circuit to assemble a detector for hidden wiring in a wall is no more difficult than the simplest electrical circuit that schoolchildren make in physics lessons, so such work is unlikely to cause difficulties even for an inexperienced craftsman.

To visually display the process of identifying existing wiring in the wall, connect the pointer device in parallel to the source-drain electrical circuit. The indicator must have a ballast resistor. The value of the resistance element can vary from 1 to 10 kOhm.

As the transistor closes, which occurs when it approaches the electrical wiring, an increase in the indicator readings will be noticeable. This will indicate that there is voltage in the cables inside the wall, and therefore an electric field.

Detection of wiring in the wall by electromagnetic radiation

Another type of homemade electrical wiring finder is a milliammeter connected to a high-resistance inductor. The latter can be made independently in an arched shape. You can also use the primary transformer winding as it, removing part of the magnetic circuit.

This meter does not require a power supply - the inductor included in its composition will contribute to the appearance of alternating current, and the milliammeter will show its presence.

Often the role of a receiving antenna is played by a sound pickup head removed from an old tape recorder, which is connected using a shielded wire to facilitate searching. The frequency of sound vibrations in this case will also be equal to 50 Hz, and the intensity of the hum coming from the speaker will be influenced by the amount of current passing through the wires and the distance from the finder to the wire.

Improved homemade identifiers

Devices for searching wiring, assembled on the basis of bipolar transistors, as well as operational amplifiers, which include parts of logic chips, have high selectivity and sensitivity.

To manufacture a device using these schemes, you need to have at least a basic understanding of radio technology in order to understand how the elements used interact with each other.

There are two main principles by which these devices work:

Harnessing the strength of the magnetic field created by wiring. In accordance with it, the sound tone of the siren changes, as well as the frequency of the visible signal. The receiving element of such a device is a component of the frequency control circuit of a single-vibrator (multivibrator) generating electrical impulses. This detector can be assembled on the basis of an operational chip, a logic chip, or bipolar transistors.
Strengthening the sound annunciator signal while simultaneously deflecting the pointer arrow. In this case, the circuit, the basis of which is a field-effect transistor or receiving antenna, is improved. The role of the latter is played by an inductor with the addition of boost stages.

Although it is not very difficult to make such a determinant, its operation is associated with certain disadvantages. These include, firstly, the narrow range of detection of hidden electrical wiring, and secondly, the need for the presence of voltage in the cables.

Search for dead wires

To locate cables in walls that are thick or consist of very dense material (for example, reinforced concrete), if it is impossible to supply voltage to them, you should use an accurate detector that operates on the principle of a metal detector.

Such devices have a complex design, and making a good finder is only possible if you are professionally versed in radio engineering, and also have measuring equipment and all the elements necessary to assemble the circuit. In addition, such work is not justified from an economic point of view. If you do not have the proper experience and components, it is better to purchase one of the popular and proven devices in the store, for example, BOSCH or Woodpecker.

Finding Hidden Wires Using Android

Did you know that if you have a tablet computer or at least an Android smartphone, you can use it to detect wiring in the wall? To do this, you need to have the appropriate software installed on your device, which can be downloaded from the GooglePlay application.

These devices are equipped with a built-in module that functions as a navigation compass. Installing the necessary program allows you to use it as a metal detector. Of course, if you are looking for buried treasure, Android will be useless, but using it to find cables hidden in the wall is quite possible if they are not too deep in its thickness.

The principle of operation of the device is clearly shown in the video:

To search for wires in thick walls, as well as in reinforced concrete panels, it makes no sense to use an Android-based device. In this case, you won’t be able to do without a professional metal detector.

Conclusion

Now you know what an electrical wiring detector is, what types of these devices there are and on what principle they work, as well as how to make a finder for hidden wiring in the wall with your own hands. If you are interested in radio engineering and like to assemble electrical circuits yourself, you will probably be intrigued by the opportunity to make such an interesting device. If assembling electrical circuits is not your hobby, then you can purchase such a detector in a specialized store.

When performing construction work, there is often a need to check the wall for the presence of wiring in it. To conduct a search, you will need a detector that reacts to metal. You can purchase this device in a factory-made version or make a hidden wiring finder with your own hands. This article will discuss the nuances of the internal structure of detectors, as well as methods for their manufacture.

Factory detector circuits

There are several types of factory-made detectors:

Electrostatic. The advantages of such a device are the simplicity of the internal structure and the ability to find metal objects at a considerable distance. The disadvantage of the detector is that it can only search in a dry environment. Otherwise there will be false positives. In addition, only those wires that are energized can be detected.
Electromagnetic. Advantages include simple circuit design and highly accurate wiring detection. There is only one drawback, but a significant one: in addition to voltage, you need a fairly powerful load - at least 1 kilowatt.
Metal detector. This device is a standard metal detector. The main advantage is that there is no need for tension. Disadvantages: detects any metal (not just wiring), and is also structurally complex.

The simplest circuits of homemade devices

There are several schemes of such devices.

With sound indication

You can make a simple hidden wiring detector with your own hands using resistor R1. This resistor protects the circuit from induced voltage. Moreover, even if you install it, this most likely will not affect the operation of the device.

Hidden wiring detector circuit with sound indication

A copper conductor with a length of 5 to 15 centimeters is used as an antenna. When wiring is detected, a specific crackling sound is produced. The piezo element is connected according to the bridge circuit principle, which allows you to control the volume level.

Sound indication combined with light

This circuit is also simple - you only need one chip.

Hidden wiring finder circuit on a microcircuit

Features of the circuit: the value of resistor R1 must be equal to or greater than 50 MOhm. The LED is used without resistance limitation, since the microcircuit performs this task independently.

On a field-effect transistor (first circuit)

Transistors of this group are extremely responsive to an electric field. This feature is used in the diagram below.

Field-effect transistor wiring finder circuit

From the picture you can understand that the device is very simple; you can make it yourself, without using any special devices. The supply voltage indicator is from 3 to 5 V. The current required is so small that the detector can operate for 5-6 hours without shutting down. The antenna coil is fixed with a 0.3-0.5 mm wire to the core, which, in turn, has a diameter of 3 mm. The number of turns depends on the wire itself: 20 turns for a 0.3 mm wire and 50 turns for a 0.5 mm wire. The antenna can function both with and without a frame.

On a field-effect transistor (second circuit)

Another option for making a hidden wiring detector with your own hands using a field-effect transistor is to use the KP103 microcircuit. This field grass is characterized by high sensitivity. If its gate is in close proximity to the wiring, the resistance is reduced, which leads to the opening of other transistors. After this, the LED starts to glow.

Note! Polevik KP103 can be used with any letter, just like the AL307 light diode. The fact is that bipolar transistors with such conductivity have low power, and the transmission coefficient must be significant. Therefore, instead of KT203, it is recommended to choose KT361.

The device is small in size - assembly can be done even in a marker housing. The antenna extends through the hole in the marker. The antenna length is from 5 to 10 centimeters. However, if the wiring is not too deep in the wall (no deeper than 10 centimeters), you can get by with the length of the field-effect transistor leg.

Hidden wiring detector circuit using transistor KP103

The KP103 transistor is installed horizontally, and the gate must be bent so that it is located directly above the transistor body.

Metal detector

Schematic diagram of a metal detector

The metal detector circuit looks like this:

frequency generator (100 kHz) - VT1;
detector - VT2;
indication - VT3, VT4.

Generator coils are wound on a ferrite core. The rod diameter is 8 millimeters. The number of turns on the first coil is 120, on the second - 45. The wire is selected as PEVTL 0.35.

The metal detector should be adjusted away from metal products. The adjustment is made using trimming resistors R3 and R5 in such a way that the generation practically disappears (uneven glow of the diode and low brightness). Next, the R3 tincture occurs in order to extinguish the emitter.

The next step is to adjust the sensitivity. This is done using a piece of metal (you can use a coin) and a pair of resistors. Moreover, it is recommended to repeat the sensitivity adjustment periodically. To optimize the process and make it more convenient, regulators can be built into the body of the metal detector.

The tuned device turns on when the antenna is close to the metal - the light diode begins to blink.

Wiring alarm without batteries

This detector uses the network directly as a power source. This circuit is possible through the use of a high-capacity capacitor (indicated in the diagram as C1). The capacitor is charged from the network. In a charged state, the capacitor transmits a voltage of 6-10 V. In this case, only the brightness of the light diode depends on the voltage, but this indicator does not affect the sensitivity of the device.

Schematic diagram of a hidden wiring finder without batteries

Wiring detector on microcontroller

The diagram above shows a hidden wiring detector built on a PIC12F629 microcontroller. The operation of the device is based on responsiveness to a magnetic field. This field is formed by current flowing through a conductor located in the wall.

The circuit can use an LED lamp or a piezo emitter. When a magnetic field is detected, a lamp lights up or a piezo emitter begins to crackle, depending on the preferred type of indication.

The advantage of the device is its ability to respond only to a frequency of 50 Hz, which is the frequency of alternating current. Thus, false alarms of the finder are excluded, since the device will not respond to other frequencies.

Two-element indicator

Schematic diagram of a two-element detector

In this case, you need a microcircuit and a light diode. You can choose DD1 as the microcircuit, and it is recommended to take HL1 for the LED. The task is to connect the leads in such a way as to create three inverters in a circuit. As a result, the device will amplify the currents that flow to the device from the alternating current field in the wiring located in the wall. When wires are detected, the diode lamp begins to glow. When moving away from the wall or breaking the chain, the lamp goes out.

There are two options for implementing the circuit:

Connection of terminals: third to eighth, second to tenth, fourth to seventh and ninth, first to fifth, eleventh to fourteenth.
Connection of terminals: third with eighth, tenth with thirteenth, first with fifth and twelfth, second with eleventh and fourteenth, fourth with seventh and ninth.

Industrial circuits of professional detectors

You can assemble a professional-level device at home. However, such equipment has a rather complex design, and its manufacture will require a lot of effort. Below are two diagrams to choose from: the first refers to an industrial device, the second to a home-made Woodpecker device.

Scheme of an industrial signaling device for hidden wiring

Scheme of a homemade wiring detector “Woodpecker”

You can also make a device like YADITE 8848. Below are two options for such a device.

Schematic diagram of the detector on TC4069UBP

Wiring locator diagram for 74HC14AP

Checking homemade wiring finders

Before using a homemade device, it is recommended to test its performance. Checking will show correct assembly.

The test is performed as follows:

We find an area where there is definitely hidden wiring. For example, it is guaranteed that there are wires in the wall leading to switches and sockets.
We check the selected area. To do this, we bring the device to the wall and observe the indication.
If the signal is received only at the point where the cable passes, the device is working properly and can be used.
If the signal appears and disappears in different directions, it means the device is faulty.

Advice! Before starting the test, the wiring must be subjected to maximum stress. To provide such a load, we connect as many electrical appliances as possible to the network. As a result, the magnetic and electric fields to which the devices respond are enhanced.

So, it is not necessary to purchase a wiring detector in a store. This device can be made at home if you follow the above diagrams.

If the wires in the house are hidden in the thickness of the wall, then sometimes you have to look for their location. Let's look at how this can be done. A self-assembled device can be an assistant in this matter. You don’t even need to be a professional in the field of electronics or a radio amateur - the simplest circuit for a hidden wiring detector allows any home craftsman to make it.

In our article we will try to avoid complex scientific and technical terms. We will try to write it in a way that everyone can understand. We will not only provide schematic diagrams of hidden wiring finders, along with the names and brands of parts for assembly, but also show how the pinouts of the elements are located.

Although repairing damaged wiring is not very difficult, it is still advisable to avoid it. Therefore, it is necessary to determine the wiring diagram in the following cases.

When remodeling a house and moving partitions, moving door and window openings.
If we are going to carry out repair work related to the installation of various elements in the thickness of the wall or ceiling. Even when hanging a picture on the wall, you can accidentally touch a wire.
If we are going to install heating devices. Although they may not be mounted on the wall, pipes and radiators are not allowed to be adjacent to electrical wires; they must be located at a distance of at least half a meter to prevent damage to the insulation from overheating.
When repairing and upgrading the wiring itself (for example, installing additional lamps or sockets).

Of course, you can simply turn off the power to the house and connect the damaged wires, but this is inconvenient and dangerous for many reasons.

It is impossible to make modern repairs without power tools; if we turn off the power supply, we will not be able to use them.
When installing fasteners in the wall, we do not know how far away they are from the wires. It is possible that, without noticing, we did not break the wire, but damaged its insulation. Then the self-tapping screw and the metal shelf it secures will be energized.
There is a possibility that we will damage the ground wire. This is not noticeable, but the devices he was going to and the people using them will be without protection.

Why do you need a wire detector?

Of course, you can find the location of the wires in other ways:

According to drawings- they are not always there and no one is insured that there were no deviations from the project.
According to the location of electrical appliances, junction boxes, sockets, switches and lamps. They are connected by straight vertical or horizontal lines. As in the previous case, this may not be the case due to the “fantasies” of unqualified electricians.
Carefully opening up the wall trim (especially those with sheet metal trim)- a labor-intensive and costly method. But if you are going to make repairs, then after removing the wallpaper you can often see traces of sealed grooves or bulges in the plaster, under which wires are hidden.

For all the above reasons, it is clear that you cannot do without an indicator of the location of electrical wiring.

Why make an indicator yourself?

For the reason that it is pleasant to use something made with your own hands. At the same time, you can save money. You can also buy the device; its price ranges from 1000 rubles for Chinese models with little functionality to 10 thousand for professional equipment.

The price of parts for self-assembly is an order of magnitude lower. In addition, almost any device circuit for detecting hidden wiring intended for radio amateurs does not contain rare elements; everything can be extracted from broken household appliances.

How does a hidden wiring finder work?

The search for hidden wiring is based on two principles:

any conductor under current emits electromagnetic radiation;
metal, even non-magnetic (aluminum and copper) affects the external magnetic field.

To search, either a conductor under current is determined by its radiation, or a magnetic field is induced and its change is determined (like metal detectors). Devices can work on one of the principles or combine two, since each of them has its own pros and cons.

Advantages and disadvantages of searching by electromagnetic radiation

The advantages include:

the device does not respond to pipes and fittings in the wall;
you can find the location of the conductor break;
the scheme is simpler.

On the downside:

the wires must be live.
After the break the wire is not visible.

Sensitivity increases if current flows through the wires (load is connected). If there is no load, then the wire is detected anyway, since alternating current passes through a kind of capacitor (capacitance) between the device and the wiring. Therefore, you can also look for the location of other cables (television, digital) by connecting an alternating current generator to them. This is the method used by signalmen.

Advice. After a break, the wire can be found by connecting the generator on the load side.

Pros and cons of working on the principle of a metal detector

There is only one plus - you can search for unconnected wires and pipes.

More cons:

more complex scheme;
less sensitivity;
It is difficult to find wires in a reinforced concrete wall.

Now let’s look at the hidden wiring detector circuits and their implementation:

Advice. Sometimes, instead of a finder, you can use a simple phase indicator. Its neon light lights up even without contact with the phase wire, when approached.

The simplest scheme

This is the simplest scheme, so we’ll talk about it first, and explain all the little things in more detail (let those who understand not laugh). Anyone can collect it if they want.

field effect transistor type KP 103 or KP 303 (designated VT);
power supply 1.5-5 V (one or more batteries);
electromagnetic telephone (designated SP);
wires;
any switch or toggle switch;
an ohmmeter (designated Ω) or an avometer (tester), although you can do without it.

The only tools you need are a soldering iron and wire cutters. For soldering, naturally, you must have solder, flux or rosin. Now let's talk more about the unclear details.

Field-effect transistor

The most important detail, in the diagram it is indicated like this:

We look at the right side of the figure, the left is not important to us, its conclusions are indicated by letters:

“Z” - shutter (the direction of the arrow indicates type p or n; we also do not take this into account now;
“I” is the source;
"C" - drain.

If no voltage is applied to the gate of the transistor, then there is a large resistance between the source and drain, and almost no current flows. Having applied voltage, we open the gate and reduce the resistance (like opening a tap on a pipe), the current begins to flow. Moreover, field-effect transistors are very sensitive; the hidden wiring detector circuit is based on this feature.

This is what this part looks like in the photo.

Transistor KP 303 has the same appearance, but differs in markings. After the numbers there is also a letter designation, we do not take it into account. A second version is available in a plastic case in the form of a prism and three flat terminals at the bottom.

How the pins are located on the body should be clear from the figure below. On it, a transistor in a metal case is depicted with the terminals down; you need to navigate by the key.

Attention. Field-effect transistors can burn out from electrostatic interference. Therefore, when working, it is advisable to ground the soldering iron and your body (using a metal bracelet and wire).

This is not a telephone set, but only a part of it (the device got its name from here), it looks like this:

They come with a body made entirely of plastic. Suitable for old rotary phones. It is located in the tube in the part that is adjacent to the ear (from which we hear the interlocutor). In order to remove the phone, you need to unscrew the decorative cover and disconnect the wires at the terminals.

The marking is not important to us except the resistance, it should be in the range of 1600 - 2200 Ohms (can be designated Ω).

The phone works on the following principle - there is an electromagnet inside, which, when current flows through it, attracts a metal membrane. Vibrations of the membrane create the sound we hear.

This is a measuring device for determining resistance.

It looks like this:

If it’s difficult to find, then we’ll do without it, the scheme will work just like that. If necessary, you can draw conclusions for connection and use a “tester” (avometer or multimeter - the same thing) during the search in resistance measurement mode. Almost everyone has this device.

Advice. A simple field-effect transistor with clamped terminals (drain and source) in the crocodiles on the avometer probes can serve as an “ersatz finder” for hidden wiring. The Avometer naturally works in resistance measurement mode.

Assembling the circuit

We assemble all the parts using a canopy using wires according to the diagram. We solder a piece of single-core wire 5-10 centimeters long onto the transistor gate. It will act as an antenna.

After assembly, you can pack everything into any suitable case, such as a plastic soap dish.

Looking for wiring

We bring the device turned on to the wall and begin to move the antenna along it. In the place where the live wire is located, a humming noise grows from the phone (like a working transformer). The closer to the wire, the stronger the sound will be.

You can more accurately find the wiring using the ohmmeter readings; when approached, it shows the least resistance. To work with an ohmmeter, turn off the power to the device.

How the device works

The whole point (as we have already said) is the high sensitivity of the field-effect transistor. The electromagnetic field induced on its gate with the antenna opens the transistor. Current is applied to the phone, and it begins to emit sound signals at a frequency of 50 Hertz (alternating current frequency).

An ohmmeter measures the resistance between source and drain. It becomes smaller as the gate signal increases.

Now let's look at more complex devices, without going too deep into the details.

On the chip

A very common hidden wiring finder circuit is based on the K561LA7 microcircuit.

Attention. The microcircuit may be designated without the letter “K” in front - this means that it is not general purpose, but special - of higher quality.

This is a digital chip with the simplest logic, but it works great as an amplifier.

Here is the circuit diagram itself with the pinout of the microcircuit:

The numbers on the diagram indicate the pin numbers.

In addition to the microcircuit itself, we also need an LED. This can be AL307 or its analogs (AL336) with any letter designation and any color, as well as a 3-15 V power supply.

Attention. If we choose a power supply greater than 3-5V, then the current through the LED must be limited by a 1-1.5 kOhm resistor connected in series.

The principle of operation is simple - a signal from the antenna is supplied to the inputs, as in the previous case, it is amplified. The fact that there is voltage at the input is indicated by the lighting of the LED. Two logic elements (AND-NOT) are connected in series, because the outputs of the microcircuit are inverse, that is, if there is a signal at the input, then there is none at the output and vice versa.

The only disadvantage of this finder is that it does not determine the distance to the wire.

It can also be mounted with a canopy and placed in any convenient building.

Having examined simple circuits of hidden electrical wiring detectors, we will also describe the design for experienced radio amateurs.

Combined hidden wiring finder

This device is a two-in-one device that can operate both in electromagnetic radiation search mode and as a metal detector.

Here is his diagram:

The selection of modes is carried out by switch S 1, which can supply voltage to one or another unit; we will consider them in turn.

Metal detector unit

It is located in the upper part (currently disabled according to the diagram) and consists of the following nodes:

Magnetic antenna on a ferrite rod (WA 1);

A generator assembled on a KT315 transistor (VT 1) and a second magnetic antenna coil (L2);

Receiver unit on the first coil of the magnetic antenna (L1), capacitor C2 with a detector on the KD522 diode (VD1);

Amplifier on microcircuit 140UD12 (DA1);

Indicator in the form of a KIPMO1B LED (others can be used instead, for example AL 307);
A pulse generator lasting up to a second based on two logical elements of a digital microcircuit of the simplest logic 561LE5 (D1 1; D 1 2);
An audio frequency generator on the two remaining elements of the microcircuit;
Piezoceramic emitter ZP-1 (VA 1).

How does a metal detector circuit work?

The generator is tuned to a frequency close to the receiver's transmission threshold. Trimmer resistors R2 and R6 are used for this.

Advice. To adjust the device during operation, it is even better to select R2 not as an adjuster, but as a variable one, with a knob displayed on the control panel of the device.

If there is metal nearby, the settings of the generator and receiver circuits change, and the generator signal passes through the receiver's frequency filter.
Additionally, the operational amplifier - comparator DA 1 has a response threshold compared to the voltage supplied from the divider across resistors R9, R10 to its second input. If this value is exceeded it starts working. The signal is amplified by the operational amplifier to a level sufficient to be perceived by the generator at D1, D2 as a logical unit and start it. The HL 1 LED is also connected to the output of the amplifier, which, when illuminated, indicates that wiring has been detected.
The signal from the first generator periodically triggers the audio frequency generator on D3, D4. A piezoceramic emitter connected to the generator output emits an intermittent signal.

Magnetic field search block

To start it, you need to set switch S 1 to the second position. This knot is much simpler. It is assembled on a second operational amplifier DA 2.

An antenna is connected to its input, and a second HL 2 LED is installed at the output. If there is interference (signal) at the antenna, the amplifier will raise its level and light up the connected LED.

Device assembly

We won’t give advice here, as the assembly instructions are useless, the techniques are the same as for installing all radio-electronic devices. It is difficult to make it with a canopy; it is better to use a printed circuit board.

Radio amateurs themselves know how to do everything. But there is one caveat - for stable operation you need to separate the magnetic and conventional antennas as far as possible.

Sometimes, if you don’t have a hidden wiring finder or the time (desire) to assemble it, you can try to find it using other devices.

Let me give you a few examples:

Let's not forget about Oersted's experiment, which discovered the relationship between magnetism and electricity. The scheme for searching for hidden wiring is as follows - we connect the load and, based on the maximum deviation of the arrow, we find the position of the wires. The main thing is that the current is significant, for example, the iron or vacuum cleaner is turned on.

A radio tuned to the maximum wavelength can respond to the wiring. The method works especially effectively if there are sources of high-frequency interference in the network.

An electrodynamic microphone connected to an amplifier; the most common electret microphones today do not operate in this way. You can also use the pickup of an electric guitar by first removing the strings from it. It is better to search using a “single-coil” (narrower, in one row) than using a “humbucker”, which has protection from external interference.

If you still have a cassette, or even better, a reel-to-reel tape recorder or player, then you can remove their head by removing it and extending the wires and look for the wires, using it to turn on the device for playback.

Attention. The magnetic head must be connected with a shielded wire.

Some people also try to search for wires using applications on their smartphone. But from personal experience I will say that the method does not work. I used the “Metal Detector” program, so she did not see the closely held wire to which a three-kilowatt motor was connected. Although maybe I'm wrong.

I hope that our article not only gave you the answer to what a hidden wiring finder circuit looks like, but also helped you assemble this device yourself. We are also glad if you understand why you need to know the location of the hidden wires. Make home repairs quickly and safely.

I sometimes have to do electrical installations of both hidden and exposed wiring. Moreover, if wiring is already laid in the walls under the plaster, when laying open wiring in a cable channel there is a risk of breaking the wire when drilling holes for attaching the cable channel. Although this risk is small and it is usually enough to navigate by the location of sockets, switches and boxes. It is much more likely to cut the wires when laying hidden wiring, when on plastered walls with already installed wiring you need to work with a grinder and make a groove to lay the wire. In order not to take unnecessary risks and not to do unnecessary work when restoring the wiring, several years ago I assembled a simple device for myself.

Schematic diagram of the detector

I was just starting to study electronics at the time and made a probe board by cutting grooves. Since when making boards in this way it is not very convenient to route the board to the transistor terminals, I lengthened the terminals with wiring, and these wiring were already soldered into the board, and the wiring itself was simplified with this approach.

Detector operation

The detector works like this: we turn on the lighting (the load) if we are looking for the wiring going to this switch, or we plug in any equipment into a socket, bring it to the place from which the wiring route should pass, let’s say to the socket and by pressing the button we move the finder perpendicular to the route and focusing on When the LED lights up and goes out, we find the approximate route of the wiring. Sometimes, for example, we need to move a socket or switch to a new location, and it is impractical to pull wires from the old place where it was located or from the box. In this case, we find the wiring, carefully open the layer of plaster, remove the wire and bring it to a new place.

The wiring finder is powered by the element 2032 inserted into a holder soldered from the computer motherboard. In the article on which I made this device, it was written that it was necessary to connect the VT1 shutter with a probe 5 cm long, when I connected it to the probe, taking a screw 5 cm long, it began to give too much error and showed the presence of wires even at a distance of 15-20 cm. After I removed the probe screw, it began to show with open wiring at a distance of 5-10 cm from the wire, with hidden 5 cm. According to the advice of one of the users who assembled the device, in order to dampen the sensitivity of the finder, you need to make 3-5 turns of wire, coming from the power supply minus, around the holder, in the same plane as the holder.

For the body of the device I took a shoe sponge box, the button was used without fixing, the LED was Soviet AL307A. Here is a drawing of a printed circuit board that I have saved, made in the sprint layout program. The wiring detector circuit is very simple and, I think, anyone can wire a printed circuit board themselves, using this signet as a basis.

Since there is a lot of electromagnetic interference in a modern apartment, which will lead to false alarms, it is recommended to reduce the sensitivity of the device by connecting the gate of the field-effect transistor to the positive (common) power wire. A 1-500 kOhm resistor, the sensitivity will depend on it. And in parallel to it you can connect a capacitor of a couple of hundred picofarads. Good luck everyone, I was with you AKV.

Discuss the article DETECTION OF HIDDEN WIRING

This article will look at the circuit of a fairly simple hidden wiring detector. Making it yourself is not difficult, since all the parts are available and the circuit is not complicated; there is also a file with a printed circuit board. This detector will help you determine the location of electrical wiring that is hidden in the wall, thereby eliminating the possibility of damage to it during certain work.

Detector circuit:

The sensitive element of the circuit is a field-effect transistor, to the gate of which an antenna is connected. You can use a transistor in any package and with any letter index. The device reacts to wires under voltage of 220 V 50 Hz, regardless of whether current flows through them or not.

The circuit also uses a microcircuit, which consists of 4 2I-NOT logic elements. It can be replaced with an imported analogue, a microcircuit. The LED on the circuit lights up when the antenna is in close proximity to a live wire.

As an antenna, you can use a piece of ordinary thin wire, 5-10 cm long. The longer its length, the greater the sensitivity of the device. The circuit consumes approximately 10-15 mA and is powered by a voltage of 9 volts. A regular Krona battery is suitable for power supply. If necessary, any piezoceramic emitter, for example, ZP-3, can be connected to pin 10 of the microcircuit, then a sound will be heard when a wire is detected.

Detector assembly

The circuit is assembled on a miniature printed circuit board measuring 40 x 30 mm, which can be made using the LUT method. The printed circuit board is completely ready for printing; there is no need to mirror it. After etching, it is advisable to tin the tracks; this will simplify the soldering of parts, and the copper will not oxidize.

Once the printed circuit board is ready, you can begin to solder the parts. You should be careful when handling the microcircuit - it is sensitive to static electricity and can be easily damaged. Therefore, we solder the socket for the microcircuit onto the board and place the microcircuit in it only after the assembly is completed.

You also need to be careful when soldering the transistor - if it is in a plastic case, then only two legs are soldered onto the board - drain and source, and the antenna is soldered directly to the gate. If the case is metal, all three legs are soldered onto the board along with the antenna.

It is important not to mix up the pinout, otherwise the device will not work. For convenience, the power wires can be immediately soldered to the connector for Krona, as I did. After completing soldering, be sure to wash off any remaining flux from the board, otherwise sensitivity may be affected. It is also advisable to check the correct installation and adjacent tracks for short circuits.

Detector tests

After assembly is completed, testing can begin. We take the crown and connect it to the board, placing an ammeter in the gap of one of the wires. The circuit consumption should be 10-15 mA. If the current is normal, you can bring the detector antenna to any network wire and watch how the LED lights up and the piezo emitter beeps, if installed.

The wire detection range is approximately 3-5 cm, depending on the length of the antenna. In this case, you should not touch the antenna, as this will significantly reduce the sensitivity. The device does not require any setup and starts working immediately after power is applied. In addition to network wires, it also responds to twisted pair cable. Happy assembly.