Universal metal detector. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Universal metal detector. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / metal detectors

Comments on the article

Purpose and opportunities

The universal metal detector is able to detect both small and large metal objects. It is equipped with several interchangeable coils with a diameter of 25 to 250 mm. This allows you to detect the location of small objects with an accuracy of millimeters at a distance of several centimeters, and large objects - at a distance of several tens of centimeters.

Schematic diagram

The schematic diagram is shown in fig. 2.23, a. The principle of its work is traditional. The metal detector contains a reference oscillator assembled from logic elements DD1.1 and DD1.3 with a generation frequency of approximately 100 kHz and a "metal-sensitive" generator on the DD1.2 element and one of the remote inductors connected to the generator via the XS1 connector.

The signals of both generators are fed to the mixer, assembled on the element DD1.4. Headphones are connected to the mixer output through the R4C4 filter, which "cuts off" the higher frequencies. To obtain a greater sound volume, the capsules of the phones are connected in series.

The metal detector is powered by a GB1 battery, but there is no power switch in its circuit - the supply voltage is supplied to the microcircuit through contacts 2, 4 when a replaceable coil is connected.

Rice. 2.23. Universal metal detector: a - schematic diagram; b - a simple charger; c - printed circuit board

Operating principle

As long as there is no metal near the remote (replaceable or search) coil, the phones will have a sound of a well-defined tonality, set by a variable resistor R2. When the coil approaches a metal object, the tone of the sound will change.

Element base and recommended replacements

In addition to that indicated in the diagram, you can use the K561LA7, K564LA7, K564LE5 microcircuits. Fixed resistors - MLT-0,125, variable R2 - SP5-2 or other small-sized. The oxide capacitor C5 can be K50-6, K53-1, the rest of the capacitors are KLS, KM. Headphones - TON-2A with volume control.

It is advisable to modify the head phones a little - install an XS2 jack from small phones on the volume control case (an XP2 plug from the same phones is inserted into this jack), after removing the wire with the plug. Then connect the capsules in series. Power source - GB1 battery is recommended to be composed of four D-0,1 or D-0,06 batteries connected in series. Since the batteries deplete over time, a simple charger is used to recharge the batteries (Fig. 2.23, b), plugged into the XS1 connector using a five-pin plug.

Metal detector design

Details of the metal detector, except for connectors, battery and variable resistor, are best mounted on a small printed circuit board (Fig. 2.23, c). This board, together with the battery 2, should be placed in a small case 3, for example, in a medicine box.

Connector 4 must be fixed on the cover of the box, and a two-wire cord should be passed through the hole in the bottom, the ends of the wires of which should be soldered to the XP2 connector. The variable resistor R2 must be fixed on the side wall of the box.

Winding replacement coils

For each of the replaceable coils, you need to wind the winding 5, which is wrapped with a layer of varnished cloth, and on top with tinned copper foil 6. The beginning and end of the foil winding should not touch each other, so a gap of several millimeters is left between them.

Then base 7 should be made from foil material in the form of a disk, on which connector 8 should be fixed by soldering. 2 and 4 connectors).

Solder the foil winding of the coil to the base so that the gaps of the winding and the annular strip of the base match. If necessary, place a capacitor C' on the base, the conclusions of which must be soldered to the terminals 3 and 1 of the connector, i.e., connected in parallel with the inductor.

After checking the coil (with an ohmmeter) and selecting the capacitor C' (when adjusting the metal detector), solder cover 9 made of foil material, made like a base with an open annular strip.

The winding must contain the following number of turns:

for a coil with a diameter of 25 mm - 150 turns of wire PEV-1 0,1;
for a coil with a diameter of 75 mm - 80 turns of PEV-1 0,18;
for a coil with a diameter of 200 mm - 50 turns of PEV-1 0,3.

Parts of the charger can be placed in the same housing that is used for generators. The appearance of the metal detector units is shown in fig. 2.23, c.

Setting up the metal detector

After making one of the replacement coils, for example, the smallest one, connect it to the XS1 connector. Set the slider of the resistor R2 to the middle position and, by connecting the headphones, select the capacitor C3 to achieve a low tone sound in them. When approaching the coil of a metal object, the tone of the sound should change. Then make a coil of a different diameter and, without soldering the cover, connect the coil to the XS1 connector. It is desirable that the inductance of the coil is 5-10% less than previously made.

By selecting capacitor C (if necessary), achieve a sound of approximately the same tone as in the first case. Similarly, coils of other sizes are made and adjusted.

Author: Nechaev I.

See other articles Section metal detectors.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive

Hemoglobin found in human skin 01.12.2023

A team of researchers from the RIKEN Center for Integrative Medical Sciences has made an important discovery by finding hemoglobin in the cells of the top layer of human skin. This protein, previously known only in the blood, is now attributed to the role of a protector, capable of protecting skin cells from the effects of ultraviolet radiation.

The discovery of hemoglobin in skin cells expands our understanding of the protective mechanisms of this organ and opens up new prospects for the development of means of protection against harmful environmental influences.

Researchers analyzed substances secreted by cells in different layers of the skin in humans and mice to understand how this organ protects itself from environmental influences. The study found that keratinocytes, which make up the top layer of skin, express hemoglobin genes in both humans and rodents.

Oxidative stress, caused by cell damage from reactive oxygen species, can lead to the formation of hemoglobin not only in the blood. Ultraviolet radiation, especially type A rays, which are responsible for 95% of solar radiation on Earth, activates the expression of hemoglobin genes in keratinocytes. This confirms the protective function of hemoglobin, presumably aimed at preventing exposure to ultraviolet rays.

A study in mice in which hemoglobin expression was blocked found markedly increased levels of reactive oxygen species in keratinocytes after irradiation, confirming the important protective role of this protein in the skin.

Other interesting news:

▪ Chickens talk about geographical discoveries

▪ Attosecond pulses of light - using a conventional industrial laser

▪ The sleep of babies

▪ Fast walking can help you live longer

▪ Blocking stolen gadgets

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Children's scientific laboratory. Article selection

▪ article Dirt-cleaning machine for a well. Drawing, description

▪ article How did the cities appear? Detailed answer

▪ article Stockrose vulgaris. Legends, cultivation, methods of application

▪ article Frequency dividers with a fractional division factor. Encyclopedia of radio electronics and electrical engineering

▪ article Improving the sound of 15GD-11A and 10GD-35. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

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