The main topics discussed
1. To build a wind rotor
Referring to the hydraulic power plant described in issues 2 and 3/2002 of the TEHNIUM magazine, it is mentioned that if the readers, amateurs of such a construction, do not have the power of water, but possibly have the power of the wind, they can make , instead of the hydraulic rotor, a wind rotor.
Of all the types of wind rotors in the world, the article proposes the realization of a rotor with vertical shaft type SAVONIUS optimized.
The rotor consists of a turbine, possibly two, the driven shaft (having on it the coupling pulley with the alternator) and the tetrapied support.
In order to achieve a simple and economical solution, it is proposed that this rotor be partially placed in the attic of the house, taking out only the turbine, on the roof cornice. In this way, it is avoided to make pyramidal towers from iron necklaces, which are very expensive.
The proposed installation is a useful device, easy to install both at home and at an institution, connecting offices, sections or access entrance. The number of remote stations that can be connected to the central unit is practically unlimited.
The advantage of this intercom is the use, at the connected stations, of the ordinary telephones (without modifications inside), both of the modern electronic ones and of the old ones with disk.
3. Economical refrigerator
Starting from a recommendation from an older issue of the "Tehnium" magazine, an automation was made that significantly improves the efficiency of any type of refrigerator.
The author of the recommendation states that the efficiency of a refrigerator is improved if a small fan is connected in parallel with the electric motor of its compressor. This external fan has the role of cooling the radiator of the refrigerator, by circulating more intense air around it.
In the summer of 2000, such an assembly was made, using the electric fan of a disused computer. The electric motor of the respective fan is asynchronous, single-phase and works at the mains voltage of 220 VC.a.
4. Speed variator for DC motors
In many practical applications it is necessary for electric motors to adjust their speed within wide limits. If the engine torque is as constant as possible, regardless of speed, it will be as good as possible.
The presented electrical diagram made with the help of an integrated circuit 555 allows the continuous adjustment of the speed of an electric motor with collector and permanent magnets in the excitation circuit, between zero and the maximum value supported by the motor.
5. Radio beacon
As it is known, radio beacons (radio beacons) are radio transmitters modulated in a certain code and have a very well stabilized frequency, which can be used for control or calibration.
Such low power (3-5 W) radio beacons are also used in amateur radiomyometry (RGA) as "foxes". The most sporty branch of amateur radio sports is the so-called "fox hunting".
6. Adjustable voltage source 0V - 27V
The proposed source is based on an integrated stabilizer of fixed voltage (+ 5V) and an operational amplifier LM 741. It was chosen to use the integrated circuit LM 309K with external control transistor.
The need for the external transistor is obvious for the case when a higher load current must be achieved (1A-4A) or when the power dissipated by the integrated circuit exceeds the allowed power.
7. Making coils with ferrite type magnetic core
Amateur builders have raised the issue of how to make coils practically, when only their inductance is given in the electrical diagram.
In order to obtain some coils with small size and superior performances, it is recommended to use ferrites in the magnetic circuit. Ferrites are magnetic materials made of metal oxides, formed at high temperatures by sintering.
Their shapes and sizes are different depending on the field of use and the required magnetic performance. Compared to the other materials intended for the realization of magnetic circuits, the ferrites present the following advantages:
- high magnetic permeability;
- very low specific remagnetization losses;
- particularly high resistivity, which automatically involves very low eddy currents, so good behavior at high frequencies;
- stability of electrical and mechanical parameters to temperature variations.
8. Temperature relay for vulcanizing and hot soldering devices with epoxy resins
For such equipment, the temperature of the platters (upper and lower) must be kept constant, at a value in the range 180-250C.
The power of both heating elements in the two platters of the press does not usually exceed 2-3 kW. A temperature regulating relay is required for each of these two resistors. The electrical diagram of such a relay is presented in the article.