When carrying out repairs or even when it is necessary to hang a clock or a picture on the wall, the work contractor has to deal with the problem of hidden cables. Of course, when laying wiring in a new house or apartment, it is advisable to draw up a diagram of its location. And such a problem will not arise in the future. However, if the repair was not major or the layout of the cables in the walls has long been lost, it is advisable to check the drilling location using a special device - a “finder”. “Finder” will help you check the drilling location
Classification of devices
There are three main types of hidden cable detectors:
- electrostatic, one of the simplest devices;
- electromagnetic, which do not react to all wires, but only to cables with a connected load;
- metal detectors that detect the presence of metal parts.
Another frequently encountered option is a combined wiring finder, which uses several methods for searching at once. Each type of these devices has its own advantages and disadvantages. And, if you have experience and desire, all of them can be made on your own.
Electrostatic finders
Devices of this type allow you to detect the electromagnetic field from live wiring. The design of these finders is the simplest. And the features of working with them include:
- the need for current in the wires. If the power is turned off, the cables cannot be detected;
- When working with the detector, you should first set the appropriate sensitivity. Otherwise, you may not detect wiring that is too deep or, conversely, constantly react to false alarms;
- Searching for wires in damp walls or inside structures with built-in fittings most often does not lead to a positive result.
The popularity of the devices is due to their low cost and acceptable efficiency. The list of devices of this type frequently purchased by consumers includes famous model Woodpecker E121, and a number of other inexpensive devices. However, you can also make them yourself - it will be even cheaper than buying a ready-made device, and will not take too much time. 
Electromagnetic devices
Signaling devices of this type allow you to locate wiring based on the electromagnetic radiation emanating from it. Like electrostatic equipment, they detect hidden cables only when energized. Moreover, for guaranteed detection it is required that some kind of electrical appliance with a power of at least 1000 W be connected to this line - which cannot be done if the hidden wire is not connected to the outlet.
Metal detectors
Metal detectors can be called one of the most effective detectors. With their help, you can detect wires even when the voltage is turned off. However, they also have a certain drawback - along with searching for metal cables, the devices also react to other metal that may be inside the wall, floor or ceiling. And by reducing the sensitivity of the equipment, you may simply not notice a sufficiently buried cable.
The principle of operation of the equipment is based on the creation of an electromagnetic field that causes disturbances inside the metal wire. The detector reacts to most metals and can be used to search not only wiring, but also other hidden parts - from screws and bolts to fittings. The cost of such a device is higher, and it is more difficult to make it at home.
Combination devices
Combined type equipment combines several (usually two) types of detectors. This significantly increases the efficiency of the search, making it possible to guarantee that there will definitely not be a single hidden cable at the drilling site. One of such devices is the TS-75 finder, the circuit of which combines a metal detector and an electrostatic version.
Equipment price
The cost of wiring detectors varies depending on models, brands and functionality. In addition, the amount that will be spent on purchasing such a finder depends on the purpose of the device, which can be domestic or industrial. It is also worth considering the country in which the device was released.
Chinese-made devices (especially of a little-known brand) will cost less - but will not necessarily serve their owner for at least several years. And European models with similar characteristics can be purchased at 3-4 times more expensive - but their sensitivity will be higher and their service life will be much longer. 
You should know: Some homemade detectors may be more effective than budget factory models.
DIY finder
For home use, a do-it-yourself hidden wiring finder is usually sufficient, the circuits of which can be called budget. And, although high accuracy cannot be achieved using such a device, its capabilities are sufficient to search for most cables inside walls and other structures. As a result, the owner of this device will receive certain savings on the purchase of an expensive detector, and will prevent damage to the electrical wire during repair work.
To assemble the easiest finder to make, you will need to prepare:
- a microcircuit that is sufficiently sensitive to electromagnetic or electrostatic radiation. For example, you can take the K561LA7 model, the purchase of which will not cause much damage to your budget;
- a piece of copper wire from 5 to 15 cm long, which will be used as a detector antenna. The best option for such a finder is an 8-centimeter segment;
3. Find a suitable housing in which the circuit will be placed, install it inside, leaving space on one side for the sound source;
4. Install a switch in the circuit, thanks to which the device can be turned on and off without removing the battery.
A properly assembled device quite effectively detects hidden wiring. When brought close to the walls, inside of which there are hidden cables, the hand-assembled device makes a slight cracking noise.
Other search methods
You can find wires hidden in enclosing structures without assembling the detector, which may require some experience in the manufacture of radio devices. To do this, use the following methods:
- visual identification of wires (tearing off wallpaper);
- using a radio receiver to search. The device is tuned to a frequency of 100 kHz, after which it is carried out near the wall. Where the hidden wire is laid, the receiver begins to make noise;
- identifying cables using sockets located on the walls. As a rule, wires run from electrical points in a straight line to the nearest corner.
Another scheme involves connecting a reel-to-reel electromagnetic microphone to a computer or tape recorder. The device may make a buzzing sound where the cable is laid. And owners of smartphones with Android OS have one more additional way - download the special Metal Sniffer program and try to use the phone as a metal detector. The operating principle of such a smartphone detector is based on the presence of a built-in compass for navigation in most models.
Summing up
Having a hidden cable detector in your apartment or house will increase the safety of repairs. And, if it is not possible to purchase an expensive finder, it can be replaced by a home-made device. Although its efficiency will be lower, and it will most likely not be possible to find the cable inside a reinforced concrete wall.
Most modern detectors are capable of operating at different frequencies. Dampers in devices are usually of the resonant type. However, oscillatory modifications can also be found in hidden wiring detectors. In this case, expanders are used with a certain throughput. On average, this parameter fluctuates around 6 microns. Thus, the sensitivity of the tester changes. The device is directly powered through batteries. They differ quite a lot in capacity.
If we consider lithium-ion analogues, then the above parameter fluctuates around 2000 mAh. To understand hidden wiring detectors in more detail, it is necessary to consider the most well-known configurations. To make your own device, you need to follow the diagrams.
Models with vibration dampers
Making a hidden wiring detector with an oscillatory damper with your own hands is quite simple. First of all, the body is selected for the model. Some people make it themselves. However, it is more advisable to use it from a broken device. The next step is to install the damper itself. To secure it to the panel you will have to use a blowtorch. Next, it is important to install the expander. The capacitors of this element are most often used of the open type.
At the same time, the models differ quite significantly in sensitivity. If we consider low-frequency modifications, then the negative resistance parameter in the circuit should not exceed 5 Ohms. In this case, the batteries are selected for 1500 mAh. Additionally, for better signal conductivity, it is necessary to install an amplifier. The regulator can be used in a rotary type detector. It is connected to the device only through a modulator.
Devices with resonant dampers
You can make a simple detector of hidden wiring with a resonant damper only using feed-through capacitors. They must be installed near amplifiers. For this purpose, threshold type resistors are used. Magnetic amplifiers are suitable for this model. However, mesh modifications are also common today. In this case, expanders can be installed even of low-frequency type. The signal conductivity parameter in the detector also depends on the power of the batteries. In this situation, many experts advise installing them of the lithium-ion type.
Reviews about low-frequency devices
The low-frequency hidden wiring detector usually receives good reviews. These devices are most suitable for home use. They are used quite rarely by construction professionals. However, during repairs they can be of great help. If you believe consumer reviews, many models can detect not only metal, but also wooden objects.
In order to independently manufacture a low-frequency detector of hidden wiring, the damper, as a rule, is selected of the resonant type. In this case, expanders are used with low throughput. In this case, the regulators are selected individually. It is best to use them from a broken tester. In this case, it is not necessary to install amplifiers.
High frequency device circuit
This type of hidden wiring detector (diagram shown below) involves the use of only oscillatory dampers. In this case, expanders are often used with high sensitivity. The minimum conductivity parameter for models should be 7 microns. In this case, negative resistance in the circuit is allowed at a level of 5 ohms. Additionally, it should be noted that devices often use wired modulators.
All this is necessary in order to connect frequency regulators to the model. Thus, the sensitivity of the device can be adjusted. Many experts recommend installing regulators directly on diodes. Amplifiers are used of frequency type. To install them, resistors are selected with low capacity. All this helps reduce fluctuations in electromagnetic interference in the circuit.
Diaphragm expander model
It is quite difficult to assemble a metal and hidden wiring detector on a membrane amplifier, but this can be done if you select high-quality capacitors. First of all, it is important to prepare a modulator for the device. In this case, the amplifier should be installed only after the damper. The capacitors on the hidden wiring detector are directly soldered low bandwidth. For adjustment, controllers that are installed in conventional testers are often used. To ensure that the signal is continuous, only open resistors are used. In this case, batteries can be used for a lithium-ion type detector. Their capacity is on average 2000 mAh.
Using Electrode Expanders
Hidden wiring detectors with electrode extenders are quite common these days. Most often, models are distinguished by increased accuracy of readings. Thus, they are well suited for builders. However, when renovating an apartment, they can also be useful. Capacitors are used directly in the models closed type. To increase the limiting frequency parameter, grid amplifiers are soldered onto the hidden wiring detector. Regulators in models are used only on conductors. They are installed exclusively through modulators. For stable operation of the detector, many experts recommend using batteries with a capacity of at least 1500 mAh.
During renovation work, quite often it is necessary to drill and break the walls in which there are passages under the plaster. electrical cables. It is not always possible to use a wiring diagram, but if it is, there may be little benefit from this - you cannot be sure that the previous owners of the premises or builders did not change the location of the wires without making changes to the diagram.
It turns out Wiring detection is an integral part of not only repair work, but also everyday life, because when driving a nail for a new painting, you can easily damage the cable.
Many unfortunate builders do not think about wiring at all when carrying out repair work, thereby violating safety regulations. The consequences of such negligence can be the most dire, so it is advisable to first identify old wiring in order to protect yourself and your loved ones from unjustified risk.
Here are the main reasons for searching for hidden wiring:
And now - consequences of neglecting safety precautions:
- short circuit;
- improper functioning of the electrical network;
- electric shock;
- fire.
In the worst case, such carelessness will lead to death.
Finding hidden wiring with your own hands: a review of the most effective methods
Most in an efficient way Of course, you will contact a specialized company - using professional equipment and many years of experience, it will not only find all the wires, but will also provide an exact diagram of their route. But such companies are not available in all cities, and such services are quite expensive, so let’s look at how you can independently find an electrical cable in the wall.
Method one. Set the maximum load on the wiring. Next, take a regular compass and, guided by the deviations of the arrow, determine the place where the electrical wire goes.
Method two. You can also mount your own device, consisting of three transistors - one field-effect and two bipolar. The first transistor will be an electric switch, a couple of others will form a multi-vibration installation. Such homemade device will pick up electromagnetic waves emanating from the wires. If wires are detected, the light on the device will light up, and the device itself will begin to vibrate.
Method three. Another version of a homemade device can be made from a field-effect transistor, batteries and a head unit (telephone, that is). To search for wiring, you need to run the transistor along the wall - if the device makes a sound, it means the cable has been found.
Method four. It is only appropriate when major renovation. Note that it is not always effective and is more suitable for rooms with “old” finishes.
Its essence is as follows: you need to remove the wallpaper or any other finishing material from the walls. Under it, if you are lucky, you will find a strip that is a different color from the rest of the wall, or represents an unevenness. This is probably where the electrical wiring runs.
Method five. Classic version, which was used before the advent of wiring finders. The radio receiver must be tuned to a frequency of 100 kHz and moved along the surface of the wall. Where the wire runs, the receiver will emit a characteristic noise resembling interference. Due to the fact that this method was popular among professional electricians, there is no reason to doubt its effectiveness.
Pay attention! During the procedure special attention Pay attention to sockets and switches - it is near them that cables mainly pass.
Method six. In this case, the electrical wiring is identified through the usual hearing aid, which makes it possible to perfectly listen to frequencies up to 50 Hz.
Method seven. As an alternative to a radio receiver, you can use a microphone, preferably an electrodynamic coil one. It must be connected to any equipment capable of capturing and reproducing the signal. The search procedure itself is no different from that using a receiver.
Method seven. You can also tie a small magnet to a string and move it near the wall. It is characteristic that this method is ineffective in panel houses and on the ceilings.
Method eight. Don't be upset if none of the methods are successful. You can always resort to reliable technology for searching electrical wiring that demonstrates one hundred percent results. We are now talking about hidden wiring detectors.
Today, wiring finders are sold in all electrical stores. By running such a device along the walls, you can easily identify not only the location of the cables, but also determine the strength of the voltage in them.
Pay attention! Such devices react to both electrical wiring and metal fittings. Therefore, it is recommended to connect a more powerful device to the electrical point to enhance the radiation.
Live electrical wiring produces an electromagnetic field. Devices for its detection are aimed at identifying the sources of this field, and built-in amplifiers make it possible to more accurately determine the location where the wire runs. But in order for the finder to perform its functions, certain rules must be followed when laying cables.
- Cables should only be laid parallel to architectural lines.
- Horizontal wires should be located at a distance of 1.5 cm from the ceiling slabs.
- If the finishing layer is thicker than 1 cm, then the cables should be laid along the shortest route.
- If you do not follow these rules during installation, it will be quite difficult to detect the wiring.
Such devices may vary in detection method and design complexity. The price range is quite wide - from 100 to 3000 rubles.
Pay attention! When identifying wires, the finder can provide both light and sound signals.
Below is a classification of detectors by design complexity.
- Devices that, in their operating principle, vaguely resemble metal detectors. They are equipped with a special coil that generates a small electromagnetic field. If a foreign electrical or iron object gets into such a field, it will immediately change.
- Devices that detect electromagnetic waves emanating from live wires.
- A hybrid of previous devices, which is very expensive, therefore it is used mainly by professionals.
According to the type of design, finders are divided into:
- screwdrivers;
- testers.
The design of testers is much more complex than that of screwdrivers. Modern models are equipped with laser pointers and are capable of detecting not only electrical wiring, but also telephone cables. Moreover, the testers will allow you to detect even underground wiring. The devices are equipped with a screen backlight, a flashlight and fuses that protect against overvoltage.
An indicator screwdriver is a simpler and cheaper device for detecting wiring, but it is effective only in cases where the wires are located at a depth of no more than 2 cm.
This screwdriver can be used in two ways:
- non-contact search allows you to determine the location of the wiring;
- contact - makes it possible to measure the voltage.
More modern models screwdrivers are equipped with a display showing voltage data; As for other devices, they use sound signals for notification.
"Woodpecker" - the most popular wiring finder
In Russia, one of the most popular devices for searching electrical wiring is considered to be the “Woodpecker” (officially, then E121). It makes it possible to determine the location of cables under plaster up to 8 cm thick.
Wiring finder "Woodpecker"
The technical features of the Woodpecker are as follows:
- operation from voltage up to 380 Volts;
- weight – 250 grams;
- possibility of contactless search;
- the ability to search for wiring, phase cables, broken electrical appliances and breaks;
- monitoring the operation of the meter and fuses;
- four sensitivity modes.
Let's take a closer look at these modes. Below is indicated distance from the device antenna to the wire for each of them:
- 1 – 0-1.5 mm;
- 2 – 10 mm;
- 3 – 30 mm;
- 4 – 40 mm.
The set with the Woodpecker device includes a case, batteries and a registration certificate.
Manufacturing a hidden electrical wiring detector
If for one reason or another it is impossible to purchase a finder, you can always make such a device yourself.
Stage one. First you need to select the body of the future device. For example, a plastic box from a fluorescent lamp may be suitable for this.
Stage three. Then you need to install 5-volt batteries, then drill a small hole in the case and insert it there LED lamp.
Stage five. All that remains is to secure the lid and test the device. It will notify you that hidden electrical wiring has been detected by a lit lamp.
Pay attention! If the wiring was laid in accordance with all requirements, then it will run vertically or horizontally.
Detecting a broken hidden wiring
If one of the hidden cables has been damaged, you can use one of two existing methods to find it.
Method one. First you need to find out which cable is damaged - neutral or phase. Here you will need an indicator screwdriver, with which you need to check all the contacts of the failed electrical point (switch or socket).
In a switch that is turned off, only one of the contacts will be energized, but in a switch that is turned on, both contacts will be energized. Regarding the socket, there will only be one live contact in it in working condition. In a word, if there is definitely a phase, then you can be sure that the neutral wire has broken.
Pay attention! If the wiring is damaged in some inaccessible place, then it is better to seek the help of specialists, since it is unlikely that you will be able to find the damaged area on your own.
Method two. If you have full access to all sections of the wiring, the problem area can be identified with an ordinary tester. Here is an approximate scheme of work.
- First, the electricity supply is turned off at the electrical panel.
- Then you need to make two notches on the wire insulation, exposing the metal - one near the outlet from the distribution box, the second two meters from the first.
- Next, using a tester, you should determine the resistance in this section of the wiring. If it is low, then there are definitely no cliffs there.
- The following sections of electrical wiring are checked in the same way until a section without low resistance is found.
Conclusions
As a result, I would like to once again note the importance of determining the location of the electrical line before starting repair work. If this is not done, then the consequences of such frivolity can be the most dire, perhaps even fatal. Therefore, you need to use one of the described methods (it is advisable, of course, to look for electrical wiring using a sensor) even when you are just hanging an ordinary picture on the wall.
In the article we will talk about simple circuits indicators of hidden wiring on transistors and microcircuits.
A device such as a hidden wiring indicator becomes necessary when repairs are being carried out in a room, and where and how the electrical wiring is installed is unknown. The probability of breaking the wiring at this time becomes quite high and the law of meanness is triggered: the electric drill drill hits the wiring exactly, which in the best case leads to its breakage, and in the worst case – damage to the electric drill or electrical injury.
To detect hidden electrical wiring, in most cases, a simple device consisting of a field-effect transistor and a pointer ohmmeter is sufficient. The principle of operation of the device is based on the property of a field-effect transistor - to change its resistance under the influence of interference at the gate terminal. When searching for hidden wiring, the transistor body is moved along the wall and the location of the wiring is determined by the maximum deviation of the device arrow.
A more advanced option is to use a field-effect transistor, a headphone and one or three batteries (see figure). Transistor VT1 - type KP103, KP303 with any letter index (in the latter, the housing terminal is connected to the gate terminal). The BF1 telephone is high-impedance, with a resistance of 1600...2200 Ohms. The polarity of connecting the GB1 battery does not matter.
When searching for hidden wiring, the transistor body is moved along the wall and the maximum sound volume with a frequency of 50 Hz (if it is electrical wiring) or radio broadcasts (radio broadcast network) is used to determine the location of the wires.
Indicators of hidden wiring on transistors
Determine the location of the hidden electrical wiring a relatively simple device made with three transistors will help in the walls of the room (see figure). A multivibrator is assembled on two bipolar transistors (VT1, VT3), and on field effect transistor(VT2) - electronic key.
The operating principle of the hidden wiring indicator is based on what is around electric wire An electric field is formed, and the finder picks it up. If the SB1 switch button is pressed, but there is no electric field in the area of the WA1 antenna probe, or the hidden wiring indicator 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 of the hidden wiring indicator, 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 battery voltage 6...9 V, push-button switch SB1 - KM-1 or similar.
The body of the Hidden Wiring Indicator 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. A switch and LED are attached to the side wall of the upper compartment, and an antenna probe is attached to the top wall. It is a conical plastic cap, inside of which there is a metal rod with a thread. The rod is attached to the body with nuts; from inside the body, a metal petal is placed on the rod, which is connected with a flexible mounting conductor to resistor R1 on the board. The antenna probe can be of a different design, for example, in the form of a loop from a piece of thick (5 mm) high-voltage wire used in a TV. The length of the segment is 80... 100 mm, its ends are passed through the holes in the upper compartment of the case and soldered to the corresponding point on the board.
The desired oscillation frequency of the multivibrator, and therefore the LED flash frequency, can be set by selecting resistors R3, R5 or capacitors C1, 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.
The wiring indicator can also be assembled according to a slightly different scheme using bipolar transistors of different structures - a generator is made on them. 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.
Parts used: C1-5...10 µF, VT1-KT209 or KT361 with any index, VT2-KP103 any index, VT3-KT315, KT503, KT3102 with any index, R1 50K-1.2M, R2 150-560 Ohm. Antenna made of wire 80…100 mm.
Indicators of hidden wiring on microcircuits
The circuit of the simplest indicator on a CMOS chip is shown in the figure.
Element DD1.1 is an electromagnetic radiation detector, and element DD1.2 is a signal repeater. When wiring is detected, the piezo emitter HA1 will operate at a network frequency of 50 Hz. A piece of copper wire 5...10 cm long serves as an antenna. The sensitivity of the detector depends on its length. If the length is more than 15 cm, this can lead to self-excitation of the circuit, so its length should not be abused.
Four A316 type galvanic cells connected in series can be used as a power source.
The following figure shows a diagram of a more complex version of the indicator on a CMOS chip, which, in addition to sound, also has a light indication of the presence of electromagnetic radiation.
It is built on a DD1 chip of the K561LA7 type, and all its elements are used. The circuit consists of the detector electromagnetic radiation on element DD1.1, low-frequency generator (operating frequency about 1 kHz) on elements DD1.2, DD1.3 and inverter DD1.4, which controls the HL1 LED. The circuit does not need to be configured.
The following indicator circuit consists of two nodes - a voltage amplifier AC, which is based on a micropower operational amplifier DA1, and 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.
When the WA1 antenna is located close to the current-carrying wire of the power supply network, the pickup of the EMF at an industrial 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 - 6...7 mA. The power source can be a 7 D-0.125 battery, “Korund” or a similar one made abroad.
Sometimes, especially when hidden 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-38B type, capacitor C1 is K50-6. The WA1 antenna is a foil pad on a board measuring approximately 55x12 mm.
The circuit board of the hidden wiring indicator is placed in a housing made of dielectric material so that the antenna is in the head part and is as far as possible from the operator’s hand. On the front side of the case there is a power switch SA1, an LED HL1 and a sound emitter BF1. The initial sensitivity of the device is set with a trimming resistor R2. An error-free mounted device does not require adjustment.
There are also more complex hidden wiring indicators, but they are needed more by professionals rather than amateurs.
When executing construction work Often there is 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 internal structure 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 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.
Pay attention! 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 carried out 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 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 configured 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 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, depending on the preferred type of indication, a lamp lights up or a piezo emitter starts to crackle.
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 relates to an industrial device, the second to homemade device"Woodpecker".
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.