Petrosani Hobby Magazine - no. 4 - 2004

Petrosani Hobby Magazine - no. 4 - 2004 - What are coils?

Reading time: 2 minute

Author: Petrosani Children's Club
Quarterly magazine of the circle of electronic constructions and amateur radio
Coordinator: Prof. Kovacs Imre - YO2LTF

The structure of the magazine

1. Pitesti National Competition 2004

Pitesti County students won a number of 5 awards (1 place I, 1 place II, 1 place III and 2 mentions). The competition proved to be at a high level both through the numerous participation of the counties in the country and through the special quality of the works made…

2. Self-protected stabilized source

The presented source allows the supply of any consumer of 60 - 70 W having the maximum working voltage 30 V.

The advantages it presents are the following:

  • continuous stabilization of the stabilized voltage, between 2.5 and 30 V;
  • continuous adjustment of the absorbed current between 0.6 and 2.5 A;
  • very good stability of the reference voltage;
  • overcurrent limitation;
  • protection from transient processes;
  • analog display of the stabilized voltage and of the absorbed current;
  • very good filtering of fog and shocks from the network.

3. Tabs from cell phone history

From time immemorial, one of the desires of people has been to be able to communicate with anyone, wherever they are. Mobile communications have fulfilled this goal, but the industry has a rather brief history, which does not cover even half a century.

The mobile phone is a hybrid resulting from the fusion of two technologies: the phone invented by Alexander Graham Bell in 1876, and the radio, invented by Nicolai Tesla in 1880 and perfected by Guglielmo Marconi in 1894.

The first individual who can be credited with creating a mobile phone prototype is the talented English inventor David Hughes, in 1879. He found that turning on and off the current in a circuit causes a click in a receiver in a separate circuit (just as the switches in our apartments produce a click in the radios in the house).

4. Coil

a) Definition

By coil is meant an electrical conductor so wrapped as to form one or more turns, in order to create a magnetic field.

b) Classification

By field of use:

  • low current coils;
  • coils for strong currents;
  • induction coils.

After construction:

  • coils without housing, when the number of turns is small and the thickness of the conductor is sufficient to ensure the rigidity of the coil;
  • coils with housing made of laminated materials.

By form:

  • cylindrical coils;
  • parallelepiped coils;
  • toroidal coils.

By frequency of use:

  • low frequency coils;
  • high frequency coils;
  • audio frequency coils.

5. Curiosities

Holograms are special three-dimensional photos, taken with the help of the laser. The images on them look like reality, because different angles give you different perspectives.

Electromagnetic waves they are made up of alternative electric and magnetic fields. The first man to realize the connection between electricity and magnetism was James Clerk Maxwell in 1864.

And more..

6. Catalog tabs

  • Equivalence table for CIS diodes (Russian);
  • Table of equivalence CSI transistors type KT - silicon.

7. Stabilized source with integrated circuit

The realization of laboratory sources for experimenting with different electronic assemblies can be easily done with the help of specialized integrated circuits.

Unlike the stabilizing integrated circuits with 3 terminals in the series 78xx, fixed voltage stabilizing circuits, with integrated circuit LM 317T a minimum adjustable voltage source can be achieved 1A...

8. Installation for checking the crystals

The assembly allows checking the operation of quartz crystals, with a frequency between 50khz and 50Mhz, in an RC oscillator assembly in which the crystal is mounted between the base and the collector of a transistor…


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