Electronic insect exterminator. Scheme, description

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Electronic insect exterminator. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Home, household, hobby

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From early summer to late autumn, the rest or entertainment of many summer residents and tourists is hindered by nightlife - clouds of flying insects, moths, etc. "Electronic" protection is suitable against them. which is not as efficient though. like pesticides, but more environmentally friendly! Below is a description of such an insect trap. Our trap comes from the "psychology of insects" that the light of an incandescent lamp lures them to itself. And here they are trying to get to the lamp through the wire mesh.

The stretched wire mesh is connected to high voltage. The individual wires are at such a distance from each other that the breakdown strength of the air is at its limit. An insect flying through the mesh reduces this distance, so a high-voltage discharge electric current passes through its body, and the insect dies. The foregoing already suggests that we are talking about such a device, where electronics - due to its extreme simplicity - is a secondary problem in comparison with the mechanical design.

Despite this, we will 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 surge filter (noise filter); - electronic regulator: - high-voltage transformer.

(click to enlarge)

The circuit (Fig. 1a) works as follows. Capacitor C2 is charged from mains voltage through diode rectifier D1 and resistor R2 to the peak mains voltage (310 V). This voltage enters through the primary winding of the transformer T] to the anode of the thyristor Th. On the other branch (R1, D2, C1), the capacitor C1 is slowly charged. When, during charging C1, the breakdown voltage of the dinistor Di is reached (within 25 ... 35 V), the capacitor C1 is discharged through the control electrode of the thyristor Th and opens it. Through an open thyristor and the primary winding T1, C2 is discharged very quickly. The pulsed alternating current induces a high voltage in the secondary winding T1, the magnitude of which can exceed 10 kV. After the capacitor is discharged, the thyristor closes and the process repeats. Permissible voltages of the elements must correspond to the values \uXNUMXb\uXNUMXbspecified in 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 the secondary winding of a horizontal-scan transformer of a black-and-white TV (known as "millstones"). The operation of the transformer in quiet times is somewhat "grouchy". However, the accompanying sound phenomena are even useful - because they indicate the presence of high voltage. for example, when the incandescent lamp in the trap burned out. In general, a silently operating device could play a cruel joke on an unsuspecting inadvertently approaching passerby. The inlet filter 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 fabrication of the wire curtain. To obtain it from any good insulating material (for example, from a textolite or plexiglass plate 4 mm thick), two disks with a diameter of 170 mm and two disks with a diameter of 150 mm are cut. Along the perimeters of each pair of discs, cuts with a depth of 10 mm (5 pieces) are made with a jigsaw every 36 °. Then the disks are marked through 120 ° and holes with a diameter of 5 mm are drilled. After that, 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 thread 50 mm long. and on the second - 30 mm long. The disks are assembled together so that the two smaller ones are on the inside and the two large ones are on the outside. Disks with small and large diameters are mounted on the threaded ends of the rods at a distance of approximately 15 mm from each other.

It is advisable to set the slots of the small and large disks in this way. so that they do not fall on the same 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, and with a shorter one - a cover. If the frame is assembled properly. the upper disks are removed, and holes for the incandescent lamp cartridge are sawn in the middle with a jigsaw. The dimensions depend on the lamp used. I used a minion lamp socket. It is also necessary to take care of such a fastening of the cartridge (for example, removable from above) so that the lamp can be replaced without disassembling the grids. For the mesh, uninsulated copper wire with a diameter of 0.45...0.5 mm was used. It must first be immediately stretched into the slots along the perimeter of the disk. If you use wire with enamel insulation, the work will increase somewhat. From it you need to remove the insulation along the entire length with sandpaper. After installing the inner and outer parts of the curtain, the ends are taken from the large and small discs 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 shape of the board must match the shape and dimensions of the plastic box. The high voltage transformer is assembled like this. 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. For the new primary winding, winding wire with a diameter of 0.8 mm is used. The number of turns is 25. Any defect-free "millstones" for a black-and-white TV are suitable for the secondary winding. High-frequency ferrite cores with about 20 turns of winding 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 "millstones".

After switching on, the lamp lights up, and the whole device quietly "grumbles", signaling the presence of high voltage. Sparks do not jump through the double wire mesh. If they still 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. Insert a screwdriver between two rows of wires - now sparks should jump on both sides of the screwdriver. The high internal resistance of the transformer winding in itself protects against a dangerous amount of current in the event of a discharge. But still, I strongly remind you to follow the rules related to working with high voltage, as in manufacturing. as well as during operation.

Touching the wire "cage" with your hands will be very unpleasant. Therefore, when placing it, you need to think about how to use the device only in the dry season. or place it where accidental contact is impossible.

Author: C.NAGYMATE, Translation by A. Belsky; Publication: N. Bolshakov, rf.atnn.ru

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