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Electronic insect killer

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Electronic insect killer

Short description.
From early summer until late autumn, the rest or entertainment of many summer residents and tourists is hampered by nightlife - clouds of flying insects, moths, etc. Against them is suitable "electronic" protection. which, although not so effective. as pesticides, but more carefully treats the environment! Below is a description of such a trap for insects.
Our trap comes from that "psychology of insects," that the light of the incandescent lamp attracts them to itself. And here they are trying to get through the wire mesh to the lamp. The drawn wire mesh is connected to a high voltage. Separate wires are at such a distance from each other that the breakdown strength of the 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 this is a device where the electronics - because of 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 Fig. 1 and is offered in two versions.

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

Scheme 1

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

Wire "curtain" and mechanical design The most critical part of our design is the very precise manufacture of a wire "curtain". To obtain it from a good insulating material (for example, a textolite or plexiglass plate 4 mm thick), two 170 mm diameter discs and two 150 mm discs are cut out. On perimeters of each pair of disks through 10 ° are made by a jigsaw of cuts in depth of 5 mm (36 pieces). Then on the disks are marked through 120 ° and holes are drilled with a diameter of 5 mm. After that, support holders are manufactured. In the test sample, these were 3 brass rods 210 mm in length and 5 mm in diameter, with 50 mm threads at one end. and on the second - 30 mm long. The disks are assembled together so that the two smaller ones are inside and the two smaller are outside. On the threaded ends of the rods are installed discs with small and large diameters at a distance of about 15 mm from each other. It is advisable to set the slots of small and large disks so. 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 discs into which the ends of the rods with a longer thread are screwed, and with a shorter lid. If the frame is properly assembled. the upper discs are removed, and in the middle of their jigsaw holes are cut for the cartridge of the incandescent lamp.

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

Installation and operation

The shape of the board must match the shape and dimensions of the plastic box.
The high-voltage transformer is assembled like this. A primary winding is removed from the "core" of the high-voltage transformer core, and a new coil is manufactured in accordance with its dimensions. For a new primary winding, a winding wire with a diameter of 0.8 mm is used. The number of turns is 25. For any secondary winding, any defectless "millstone" is suitable for a black and white TV.
For a protective filter, high-frequency ferrite cores with approximately 20 turns of a winding wire with a diameter of 0.6 ... 0.8 mm are best suited. After the final installation of the electronics board, a network cable is connected, and the wire curtain is connected to the "mill mill". After turning on the light comes on, and the entire device silently "grumbles", signaling the presence of high voltage. Through a double wire mesh, sparks do not slip. If still skip, then either the voltage is too high. or the rows of wires are too close to each other. For fixed geometric dimensions of the "curtain" the required voltage is set by the adjustment of the electronic circuit. The test ends with a spark test using a screwdriver. Insert a screwdriver between two rows of wires - right now, sparks must flow from both sides of the screwdriver. The large internal resistance of the winding of the transformer itself protects against a dangerous amount of current when a discharge is generated.
But still, I strongly urge you to observe the rules related to working with high voltage, as in the manufacture. and during operation. Touching your hands with a wire "cage" will be very unpleasant. So, when you place it, you need to think about how to use the device only in the dry season. or place it where there is no chance of touching.