A simple beating metal detector. Scheme, description

Free technical library

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

A simple beating 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 functions performed

This device helps to detect large metal objects at a depth of up to 0,8 m. It is often needed by builders, gas service and public utilities workers to search for pipes, manholes and well covers that are under a layer of asphalt, earth or snow.

Operating principle

The principle of operation of the device is based on measuring the beats of two frequencies obtained from the reference and search generators. When the frame with the coil of the search generator approaches metal objects, its inductance changes, and with it the frequency of the search generator also changes. As a result, the beat frequency in the headphones also changes.

The device is powered by the Krona battery, consuming a current of 5-8 mA.

Schematic diagram

Schematic diagram of the metal detector is shown in fig. 2.33 a.

A simple beating metal detector
Rice. 2.33. A simple metal detector: a - a circuit diagram; b - schematic diagram of the probe generator

The search generator is assembled according to the so-called "capacitive three-point" scheme on the elements D1.1 and D1.2. Its frequency is determined by the elements of the L1C2 contour. A buffer stage is assembled on element D1.3 of the microcircuit, element D1.4 serves as a mixer. The reference oscillator is built according to the scheme of an inductive three-point on a field-effect transistor V2 of the KP303 series. Its frequency depends on the ratings of the coil L2 and capacitor C9, as well as the capacitance of the varicap V1. The load of the device is the coil L2.

Coils

Coil L1 contains 100 turns of PEV-2 0,27 wire wound on a ring with a diameter of 250 mm, made of a vinyl plastic tube with a diameter of 16 mm. The winding is wrapped with a layer of aluminum foil with a gap between the beginning and end of 4-6 mm, so that a short-circuited coil does not form. The foil is connected to the "negative" terminal of the coil.

Coil L2 consists of 150 turns of PELSHO 0,14 wire wound on a K8 x 6 x 2 ring made of 1000NN grade ferrite. The tap is made by a third of the turns, counting from the grounded pin. Coil L3 is wound on the same ring, with the same wire until it is filled.

Coil L3 serves as the load of the device.

Device design

The device is mounted on a board made of one-sided foil fiberglass 1,5 mm thick, 55 x 65 mm in size (Fig. 2.34, a).

A simple beating metal detector
Rice. 2.34. A simple metal detector: a - printed circuit board; b - arrangement of elements

Element base and recommended replacement parts

The device uses resistors - MLT-0,25, MLT-0D25 with a deviation of ± 20%. Capacitors C2-C5, C8, C9 - KM6-4B, C12 - K50-6, the rest - K10-7V. Varicap V1 - any of the D901 series.

Instead of the KP303E transistor, you can use a similar one, with any other letter index.

Arrangement of elements

The location of the parts on the board is shown in fig. 2.34b.

Setting up a metal detector

Setting up the device consists in checking the performance of both generators using a wavemeter or an oscilloscope. If necessary, by selecting the capacitance C2, you can tune the L1C2 circuit to a frequency of 100 kHz. Using capacitor C9, the frequency of the reference oscillator can also be adjusted to 100 kHz with the middle position of the resistor R2 slider. At the same time, a whistle emitted by beats should be heard in the headphones.

If there is no wavemeter, the presence of high-frequency oscillations can also be verified using a simple probe (its diagram is shown in Fig. 2.33, b).

If the generators are working, then when the probe is connected to terminals 12 and 13 D1.4, the indicator arrow will deviate by a certain amount, depending on its sensitivity.

Author: Sketeris R.

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

black tomatoes 15.05.2009

English geneticists from the Center for Biotechnology in Norwich, having introduced the snapdragon gene to tomatoes, bred a variety of almost black color. It is rich in anthocyanins - dark plant pigments, which are abundant, for example, in blueberries, black grapes, blackberries, black currants.

These substances, which neutralize the destructive effect of free radicals, have anti-inflammatory properties, improve vision, significantly slow down the growth of certain tumors, and protect against cardiovascular diseases.

Experiments on mice of a special line, often suffering from cancer, showed that eating ordinary tomatoes extended the life of sick mice from 142 days to 146, and mice that ate black tomatoes lived an average of 182 days. Normal healthy laboratory mice live up to 211 days, and when consuming black tomatoes, up to 260.

Other interesting news:

▪ Lynx in the water

▪ A tomograph is more efficient than a polygraph

▪ 3D printer with voice control

▪ Caterpillars can eat plastic waste

▪ Cypress trees under the sand

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Lighting. Article selection

▪ article A parable by the town. Popular expression

▪ Article How do seeds germinate? Detailed answer

▪ article Footwear tourist. Travel Tips

▪ article Antenna design Double square. Encyclopedia of radio electronics and electrical engineering

▪ article First red, then white. Focus secret

Leave your comment on this article:

All languages of this page

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