Simple hidden wiring finder without power supply. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Electrician

Simple hidden wiring finder without power supply. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Electrician's Handbook

Sometimes in everyday life it becomes necessary to determine the location of electrical wiring in the walls or ceilings of buildings. The journal "Radio" published many articles describing such devices, both stand-alone [1-6] and in the form of prefixes to the multimeter [7, 8]. However, they all require a power source or are powered by a multimeter, which, however, also has its own source.

Is it possible to make a seeker that does not require a power source? It is clear that such a device should at least have an indicator. It is also intuitively clear that this indicator should be micro-powerful and preferably optical. From the whole variety, you can choose gas discharge lamps (neon), LEDs and LCDs. In neon lamps, the current is tenths of a milliamp, but the ignition voltage is very high - tens of volts. Among the LEDs, you can find devices with a current of tenths of a milliamp and a voltage of 1,5 ... 2 V. However, according to the author, the most economical are LCDs. They consume current from units to tens (sometimes hundreds) of microamperes at a voltage of one volt. In addition, unlike LEDs, they do not need a constant voltage, which means that there is no need for a rectifier.

So, the indicator is selected. What's next? How to make it indicate the presence of an alternating electric field, given that the seeker should not have a galvanic connection with the wiring?

Recall that usually electrical wiring is made with a cable with two or three insulated wires with a diameter of 1 ... 2 mm in common insulation. One of the wires is zero or neutral, the second is phase with an effective (rms, effective) voltage of 230 V relative to zero, the third is grounding (it is not in a two-wire cable). Sometimes, extremely rarely, there are situations when the voltage in the network is formed by two phase wires. In any case, we can assume that at some distance from the wires, exceeding their diameter and the distance between them, an alternating electric field is created by two wires with a voltage of 230 V between them.

Simple hidden wire finder without power supply
Rice. 1. Diagram of the device

Considering that the LCD, as an element of the electrical circuit, is similar to a capacitor [9], consider the circuit in Fig. 1. On it SZhKI - the capacity of the LCD (one element relative to the total output); 1 and 2 - network wires; 3 and 4 - points to which LCD outputs are connected; C1-C4 - capacitors formed by network wires and connection points of LCD outputs. Taking into account the fact that, in the first approximation, at a great distance, exceeding the distance between the network wires, the capacitance of capacitors C1-C4 can be considered the same, we get

C=C_LCD (U_LCD/(U_c- OR_LCD)),

where C is the capacitance of capacitors C1 -C4; U_LCD - LCD voltage; U_c - mains voltage.

A single-digit seven-element LCD FP-056P was chosen as an indicator. Measurements showed that the capacitance of its element g relative to the common output is slightly less than 80 pF, and the "ignition" voltage of the element does not exceed 3 V. Substituting these values into the formula, we find that the capacitance of capacitors C1-C4 must be at least 1 pF. Such a capacitance can be provided, for example, by a piece of cable with two cores with a diameter of 1 mm in common insulation, approximately 150 ... 200 mm long, at a distance of 20 mm from the mains wires. However, it should be taken into account that such a cable has its own linear capacitance, which should be added to the capacitance of the LCD, since they are connected in parallel.

For example, the measured linear capacitance of a cable with two cores with a diameter of 1 mm, a distance between them of 2 mm and in PVC insulation is about 70 pF / m. This means that a piece of such a wire 150 mm long has a capacitance of about 10 ... 15 pF. The conducted experiments showed that in real situations, to search for hidden wiring, the length of the searcher wires must be at least 350 ... 400 mm. It is extremely inconvenient to work with such a finder, in addition, the electrical wiring must have straight sections of such a length, which is far from always done in practice. It is possible, of course, to separate the wires from each other at a greater distance, thereby reducing their own capacitance, but as experiments show, without reducing the sensitivity, the length of the wires cannot be significantly reduced.

Is it possible to replace the wires with something else? From the course of the theoretical foundations of electrical engineering, it is known that the capacitance of a wire over an infinite conducting plane is twice that of two wires spaced at the same distance. It can be assumed that the capacitance of a wire located above a plate of finite width will have some intermediate value between these extreme cases. Therefore, the wires can be replaced by plates, which should provide the necessary capacitance.

The problem of calculating the capacitance between two plates of the same width lying in the same plane was solved in [10]. There is also a graph of the dependence of the linear capacity on the ratio of the distance between the plates to the width of the plate (Fig. 9.4 on p. 227). Please note that to get linear capacity in picofarads per meter, you need to multiply the capacitance value from this graph by 8,86. Preliminary calculations showed that to indicate the presence of an alternating electric field at a distance of about 20 mm from the wires, plates with a width of 15 ... cable) with a gap of 20...2 mm between them and a length of 3...200 mm. An increase in the length of the plates also leads to an increase in the sensitivity of the device.

Simple hidden wire finder without power supply
Rice. 2. PCB drawing of the finder

Based on this, it was decided to assemble the seeker on a printed circuit board. Its drawing is shown in Fig. 2, it is made of fiberglass with a thickness of 1,5 mm foiled on one side. In the middle of the board, parallel to the wide sides, the foil is removed to a width of 2 mm. The resulting two areas are points 3 and 4 in Fig. 1. Measurements showed that the capacitance between two pads 205 mm long and 16,5 mm wide is about 6 pF, respectively, the linear capacitance is about 30 pF / m, which is more than half the linear capacitance of two wires in common insulation, which was speech above. A common output of the LCD is soldered to one site on the board, and the output of the g element is soldered to the other. This is done in order for the g element to indicate the direction of the electrical wires. Such a finder confidently "recognizes" the presence of electrical wiring at a distance of 15 ... 20 mm, which is quite enough for practice.

If one “lit” element is not enough for someone, you can connect two located at the edges - elements a and d (pins 7 and 2 of the FP-056P LCD), leaving the common pin unconnected. In this case, the "ignition" voltage will double, but the total capacitance of the LCD will decrease by half, since its elements will be connected in series. Experiments with such inclusion of two elements showed that the sensitivity of the seeker did not change noticeably, but an "unpleasant" effect appeared associated with the chaotic and unpredictable inclusion of unconnected elements, although it can be considered positive, since there is an additional indication of the presence of an alternating electric field.

It is very simple to use the finder: you need to attach the board to the wall and move it, turning it at small angles in opposite directions. According to the maximum "glow" of the element or elements, the location of the "occurrence" of the electrical wiring is determined (Fig. 3).

Simple hidden wire finder without power supply
Rice. 3. Using the finder

You can increase the sensitivity (increase the distance at which the finder "feels" the wiring) by touching one of the board pads with your finger. In this case, one of the terminals of the LCD is connected to the ground through the human capacitance.

Since in most cases the neutral wire of the electrical wiring is also connected to ground, theoretically the capacitance of capacitors C1 and C3 (or C2 and C4, depending on which LCD terminal is touched) for normal operation of the finder may be less. True, this is possible only if the capacity of a person is greater than the capacity of C1 and C3 (or C2 and C4), which is far from always true. First of all, it depends on the environment, on the location of a person relative to grounded structures, mainly heating pipes and plumbing or reinforcement of reinforced concrete structures, as well as on the location of the electrical wiring itself. In any case, it's worth a try!

Literature

Gordeev V., Pavlov L. How to detect hidden wiring? - Radio, 1981, No. 4, p. 54, 55.
Ognev V. A simple hidden wiring finder. - Radio, 1991, No. 8, p. 85.
Voronenkov V. A simple hidden wiring finder. - Radio, 2002, No. 1, p. 56.
Makeev D. Small-sized concealed wiring finder. - Radio, 2004, No. 3, p. 56, 57.
Potapchuk M. Microcontroller wiring finder. - Radio, 2006, No. 2, p. 44, 45.
Nechaev I. Finder of hidden electrical wiring based on a lawn lamp. - Radio, 2014, No. 4, p. 48, 49.
Nechaev I. Hidden wiring finder based on digital multimeter. - Radio, 1998, No. 5, p. 41, 42.
Podushkin I. A simple hidden wiring finder - an attachment to a multimeter. - Radio, 2013, No. 6, p. 33, 34.
Yushin A. LCD digital sign indicators. - Radio, 1985, No. 6, p. 59, 60.
Bins K., Laurenson P. Analysis and calculation of electric and magnetic fields. Per. from English. - M.: Energy, 1970.

Author: I. Podushkin

See other articles Section Electrician's Handbook.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Wireless speaker Samsung Music Frame HW-LS60D 06.05.2024

In the world of modern audio technology, manufacturers strive not only for impeccable sound quality, but also for combining functionality with aesthetics. One of the latest innovative steps in this direction is the new Samsung Music Frame HW-LS60D wireless speaker system, presented at the 2024 World of Samsung event. The Samsung HW-LS60D is more than just a speaker system, it's the art of frame-style sound. The combination of a 6-speaker system with Dolby Atmos support and a stylish photo frame design makes this product the perfect addition to any interior. The new Samsung Music Frame features advanced technologies including Adaptive Audio that delivers clear dialogue at any volume level, and automatic room optimization for rich audio reproduction. With support for Spotify, Tidal Hi-Fi and Bluetooth 5.2 connections, as well as smart assistant integration, this speaker is ready to satisfy your ... >>

A New Way to Control and Manipulate Optical Signals 05.05.2024

The modern world of science and technology is developing rapidly, and every day new methods and technologies appear that open up new prospects for us in various fields. One such innovation is the development by German scientists of a new way to control optical signals, which could lead to significant progress in the field of photonics. Recent research has allowed German scientists to create a tunable waveplate inside a fused silica waveguide. This method, based on the use of a liquid crystal layer, allows one to effectively change the polarization of light passing through a waveguide. This technological breakthrough opens up new prospects for the development of compact and efficient photonic devices capable of processing large volumes of data. The electro-optical control of polarization provided by the new method could provide the basis for a new class of integrated photonic devices. This opens up great opportunities for ... >>

Random news from the Archive

DNA and premature aging 09.05.2015

All people age differently, some faster, some slower, but, taken as a whole, signs of old age appear in everyone at about the same age. With one exception: in the event that a person is sick with progeria, he begins to age extremely early. This disease has two variants, children's and adults, children's is called Hutchinson-Gilford syndrome, adult - Werner's syndrome.

Children with progeria suffer from diseases characteristic of old age: thinning and wrinkling of the skin, baldness, cardiovascular diseases, lipid metabolism disorders, atherosclerosis, joint problems, etc. They have a sharp slowdown in growth and develop a characteristic appearance: large head, small pointed face, underdeveloped lower jaw. On average, patients with a childhood form of progeria live no longer than 12-13 years.

People with adult progeria live longer, but they also experience age-related changes much earlier than usual - in their 20s, hair begins to gray and fall out, by the age of 30, cataracts, osteoporosis, and other diseases, such as diabetes, develop, and usually a person with Werner's syndrome does not live past 60 years of age. It is known that, at least in the severe form, much of the same molecular changes occur in the cells as during normal aging, so if we find a way to slow down progeria, it may give us a tool against aging in general.

The secrets of the disease could be understood by observing the stem cells that were obtained from sick people. Some time ago, researchers from the Salk Institute for Biological Research were able to turn the skin cells of children with Hutchinson-Gilford syndrome into an analogue of embryonic stem cells, the so-called induced pluripotent stem cells. Further, it was possible to experiment with them, finding out what was wrong in the stem processes in patients with progeria. But when they tried to do the same with the cells of patients with Werner's syndrome, nothing came of it - their cells were too damaged by the disease to withstand a return to the stem, undifferentiated state. Then Juan Carlos Izpisua Belmonte (Juan Carlos Izpisua Belmonte), along with colleagues from the Chinese Academy of Science and Peking University, took a different path - they modeled progeria in initially healthy cells.

It is known that Werner's syndrome is accompanied by mutations in the WRN gene, which is involved in the processes of DNA copying and repair. And so, in order to create a model of the disease, the researchers simply broke this gene in stem cells from a human embryo. Embryonic cells in the course of development turn into more specialized varieties, which in the future can give rise to one or another tissue - for example, into mesenchymal stem cells, the "ancestors" of adipose tissue, cartilage and bones. In an article in Science, the authors write that when stem cells with a non-functioning WRN gene turned into mesenchymal ones, they immediately began to age dramatically: a lot of damage accumulated in their DNA, they stopped dividing, and, finally, their telomeres were greatly shortened. This is the name of the ends of chromosomes, which, when copying DNA, protect genes from damage associated with the peculiarities of the work of the protein copier. Telomeres shorten with each cell division, and therefore they are considered something like a molecular clock that measures the lifespan.

However, cells with Werner's syndrome had another feature that most of all attracted the attention of the authors of the work. It is known that DNA in the cell nucleus is in complex with proteins. Some of them perform some kind of ongoing work on certain genes (for example, they synthesize RNA), while others play a structural role, maintaining rather large fragments of chromosomes in a packed state. The packaged, structured portion of DNA is called heterochromatin. And it turned out that in sick cells there is very little heterochromatin - in other words, DNA with Werner's syndrome comes to a free, "disheveled" state.

The same can be observed during normal aging: when the state of chromosomes was compared in several people of different ages, they saw that the older a person is, the worse his DNA is packed in the nuclei. Obviously, with progeria, the same process occurs faster and begins earlier - perhaps already in the early stages of individual development. Why can a disordered, unpacked state of chromosomes lead to such consequences? If a gene is in a heterochromatic form, this means that it is inactive, turned off, is in a dormant state. If the packaging weakens, then our genes will start to turn on, which should be silent. Just such unnecessary activity can collectively lead to aging. On the other hand, it is known that in a heterochromatic, sealed form there are mobile genetic elements that jump from place to place in DNA, thereby causing unwanted mutations.

Whether the general unpacking and disorder in DNA really entails all those changes that are characteristic of aging cells, and whether this happens in all cases of progeria, both childhood and adult, will be shown by further experiments. But, if this is true, biologists could focus on DNA packaging as a potential drug target that could help delay aging, both premature and normal.

Other interesting news:

▪ The moth's eye will help create an anti-reflective coating

▪ DC-DC Converter EL7566

▪ Sony a42 II full frame 99MP camera

▪ Space amethyst in a dying star

▪ Alternative energy has fallen sharply

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Household electrical appliances. Selection of articles

▪ article The state of the biosphere and human health. Basics of safe life

▪ article What is the difference between a broker, a dealer, a broker? Detailed answer

▪ article Linear pipeline. Standard instruction on labor protection

▪ article Metronome-conductor. Encyclopedia of radio electronics and electrical engineering

▪ article Three cards (Find a lady). Focus Secret

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews