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Electronic insect killer

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Electronic insect killer

Short description.
From early summer to late autumn, the nightlife is interfering with the recreation or entertainment of many summer residents and tourists — clouds of flying insects, moths, and so on. Electronic protection is suitable against them. which although not as effective. as toxic chemicals, but more respectful for the environment! Below is a description of such a trap for insects.
Our trap comes from the "insect psychology" that the incandescent light attracts them. And here they are trying to get to the lamp through the wire mesh. The tensioned wire mesh is connected to high voltage. Separate wires are at such a distance from each other that the breakdown strength of air is at the limit. An insect flying through a grid reduces this distance, therefore an electric current of a high-voltage discharge passes through its body, and the insect dies. What has been said above makes it possible to suspect that it is a question of such a device, where the electronics, due to its extreme simplicity, are a minor problem in comparison with the mechanical design. Despite this, we first consider the electrical circuit, which is shown in Figure 1 and is offered in two versions.

This scheme is divided into the following main blocks: - network barrier filter (interference filter); - electronic regulator: - high-voltage transformer.

Scheme 1

The scheme (Fig.1a) works as follows. Capacitor C2 is charged from the mains voltage through a diode rectifier D1 and a resistor R2 to the amplitude voltage of the network (310 V). This voltage passes through the primary winding of the transformer T] to the anode of the thyristor Th ,. On the other branch (Rl, D2, C1), capacitor C1 slowly charges. When, during charging C1, the breakdown voltage of the diistor Di is reached (within 25 ... 35 V), the capacitor C1 is discharged through the control electrode of the thyristor Th and opens it. Through the open thyristor and the primary winding T1 C2 is very quickly discharged. The pulsed variable current induces in the secondary winding T] a high voltage, the magnitude of which may exceed 10 kV.
After the discharge of the capacitor, the thyristor closes and the process repeats. The permissible stresses of the elements must correspond to the values ​​indicated on the diagram. The most important problem is the manufacture of high-voltage transformer.
You can use a ready-made high-voltage winding, which is nothing more than the secondary winding of a black-and-white horizontal television transformer (known "millstone").
The operation of the transformer in a quiet time is somewhat "grumbling." However, the accompanying sound phenomena are even useful - because they indicate the presence of high voltage. for example, when the incandescent lamp burned out in a trap. In general, a noise-free device could play a cruel joke with an unsuspecting carelessly approaching passerby. The barrier inlet filter is a necessary satellite of any thyristor controlled circuit. The device creates radio and TV interference, and the filter unit makes it easy to watch radio and television programs.

Wire "curtain" and mechanical design The most critical knot of our design is a very accurate manufacture of wire "curtain". To obtain it from any good insulating material (for example, from a textolite or Plexiglas plate with a thickness of 4 mm), two disks with a diameter of 170 mm and two disks with a diameter of 150 mm are cut out. Along the perimeters of each pair of discs, 10 ° jigsaws are made with a jigsaw, 5 mm deep (36 pieces). Then on the disks are marked through 120 ° and the holes with a diameter of 5 mm are drilled. After that, the support holders are made. In the prototype, these were 3 brass rods 210 mm long and 5 mm in diameter, at one end of which there was a 50 mm long thread. and on the second - a length of 30 mm. The disks come together so that the two smaller ones are inside, and the two larger ones are outside. On the threaded ends of the rods are mounted discs with small and large diameters at a distance of approximately 15 mm from each other. It is advisable to install small and large disk slots. so that they do not fall on one line, but are shifted to the middle of each other by about 15 mm. The bottom of the frame will be those disks into which the ends of the rods with a longer thread are screwed in, and with a shorter one - with a cover. If the frame is properly assembled. the upper discs are removed, and in their middle with a jigsaw sawn holes for the lamp holder bulbs.

Dimensions depend on the lamp used. I used a lamp holder for a minion lamp. It is also necessary to take care of such a fastening of the cartridge (for example, removable from above), so that you can replace the lamp without dismantling the grid. For the grid was used uninsulated copper wire with a diameter of 0.45 ... 0.5 mm. It must first immediately stretch into the gap along the perimeter of the disk. If you use a wire with enamel insulation, the work will increase somewhat. From it you need to remove the entire length of the insulation sandpaper. After installing the inner and outer parts of the curtain, the ends are taken from the large and small disks and connected to the ends of the high voltage winding.
The finished design is fixed on a suitable plastic box in which the electronics are placed.

Installation and operation

The form of the board must comply with the shape and size of the plastic box.
A high voltage transformer is assembled like that. The primary winding is removed from the core of the high-voltage transformer extracted from the TV, and a new coil is made in accordance with its dimensions. A winding wire with a diameter of 0.8 mm is used for the new primary winding. The number of turns is 25. Any defect-free “millstone” for a black and white TV is suitable for the secondary winding.
High-frequency ferrite cores with approximately 20 turns of magnet wire with a diameter of 0.6 ... 0.8 mm are best suited for a barrier filter. After the final installation of the electronics board, the network cable is connected and the wire curtain is connected to the millstone. After turning on the light comes on, and the whole device quietly "grumbles", indicating the presence of high voltage. Sparks do not slip through the double wire mesh. If, however, they slip, then either the voltage is too high. or the rows of wires are too close together. With fixed geometric dimensions of the curtain, the required voltage is set by adjusting the electronic circuit. The test ends with a spark test with a screwdriver. Slide a screwdriver between the two rows of wires - now sparks must slip on the screwdriver from both sides. The large internal resistance of the transformer winding itself protects against the dangerous magnitude of the current during the formation of a discharge.
But still, I strongly remind you of the observance of the rules associated with working with high voltage, as in the manufacture. and during operation. Touching the wire to the cage will be very unpleasant. Therefore, when placing it, it is necessary to think about using the device only during the dry season. or place it where it is impossible to random touch.