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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Electronic match. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Home, household, hobby So it is conditionally possible to call an electric lighter used to ignite gas in burners of gas stoves. A very convenient and safer fire-fighting device than household matches used for this purpose. In principle, you can buy an electric lighter - if, of course, it ends up in a hardware store. But it can be made with your own hands, which is more interesting from a technical point of view, and you will need a little radio components. Two variants of a home-made electronic "match" are described below - powered by an electric lighting network and powered by one small-sized D-0,25 battery. In both versions, reliable ignition of the gas is carried out by an electric spark created by a short current pulse of 8 ... 10 kV. This is achieved by appropriate conversion and increase in the voltage of the power source. The schematic diagram and design of the network lighter are shown in fig. 1.
The lighter consists of two nodes interconnected by a flexible two-wire cord: an adapter plug with capacitors C1, C2 and resistors R1 R2 inside and a voltage converter with a spark gap. Such a constructive solution provides it with electrical safety and a relatively small mass of that part of it, which is held in the hand when the gas is ignited. How does the device work in general? Capacitors C1 and C2 act as elements that limit the current consumed by the lighter to 3 ... 4 mA. While the SB1 button is not pressed, the lighter does not consume current. When the contacts of the button are closed, the diodes VD1, VD2 rectify the alternating voltage of the network, and the rectified current pulses charge the capacitor C3. For several periods of mains voltage, this capacitor is charged to the opening voltage of the VS1 dynistor (for KN102Zh - about 120 V). Now the capacitor is quickly discharged through the low resistance of the open dinistor and the primary winding of the step-up transformer T1. In this case, a short current pulse appears in the circuit, the value of which reaches several amperes. As a result, a high voltage pulse appears on the secondary winding of the transformer and an electric spark appears between the electrodes of the spark gap E1, which ignites the gas. And so - 5-10 times per second, i.e. with a frequency of 5 ... 10 Hz. Electrical safety is ensured by the fact that if the insulation is broken and one of the wires connecting the adapter plug to the converter is touched by hand, the current in this circuit will be limited by one of the capacitors C1 or C2 and will not exceed 7 mA. A short circuit between the connecting wires will also not lead to any dangerous consequences. In addition, the arrester is galvanically isolated from the network and is also safe in this sense. Capacitors C1, C2, the rated voltage of which must be at least 400 V, and the resistors R1, R2 shunting them, are mounted in the adapter plug housing, which can be made of sheet insulating material (polystyrene, plexiglass) or use a plastic box for this supply dimensions. The distance between the centers of the pins with which it is connected to a standard power outlet must be 20 mm. The rectifier diodes, capacitor C3, dynistor VS1 and transformer T1 are mounted on a printed circuit board measuring 120 x 18 mm, which, after checking, is placed in a plastic case-handle of the appropriate size. The step-up transformer T1 is made on a 400NN ferrite rod with a diameter of 8 and a length of about 60 mm (a segment of the rod intended for the magnetic antenna of the transistor receiver). The rod is wrapped with two layers of insulating tape, on top of which the secondary winding is wound - 1800 turns of wire PEV-2 0,05-0,08. Winding in bulk, smooth from edge to edge. It is necessary to strive so that the serial numbers of the overlapped turns in the wire layers would be from one hundred. The secondary winding is wrapped along its entire length with two layers of insulating tape and 10 turns of PEV-2 0,4-0,6 wire are wound on top of it with one layer - the primary winding. Diodes KD105B can be replaced by other small ones with a permissible reverse voltage of at least 300 V or diodes D226B, KD205B. Capacitors C1-C3 types BM, MBM; the first two of them must be for a rated voltage of at least 150 V, the third - at least 400 V. The structural basis of the spark gap E1 is a piece of metal tube 4 100 ... 150 long and 3 ... 5 mm in diameter, at one end of which rigidly fixed (mechanically or by soldering) metal thin-walled cup 1 with a diameter of 8...10 and a height of 15...20 mm. This glass, with slots in the walls, is one of the electrodes of the arrester E1. Inside the tube, together with a heat-resistant dielectric 3, for example, a fluoroplastic tube or tape, a thin steel knitting needle 2 is tightly inserted. Its pointed end protrudes from the insulation by 1 ... 1,5 mm and should be located in the middle of the glass. This is the second, central, spark gap electrode. The discharge gap of the lighter is formed by the end of the central electrode and the glass wall - it should be 3 ... 4 mm. On the other side of the tube, the central electrode in the insulation must protrude from it by at least 10 mm. The tube of the arrester is rigidly fixed in the plastic case of the converter, after which the electrodes of the arrester are connected to the terminals of the winding II of the transformer. Soldering points are securely insulated with pieces of PVC tube or insulating tape. If you do not have a KN102Zh dinistor at your disposal, you can replace it with two or three dinistors of the same series, but with a lower turn-on voltage. The total opening voltage of such a chain of dinistors should be 120 ... 150 V. In general, the dinistor can be replaced with its analogue, composed of a low-power trinistor (KU101D, KU101E) and a zener diode, as shown in fig. 2.
The stabilization voltage of a zener diode or several zener diodes connected in series should be 120 ... 150 V. The diagram of the second version of the electronic "match" is shown in fig. 3.
Due to the low voltage of the G1 battery (D-0,25), a two-stage power supply voltage conversion had to be applied. In the first such stage, a generator operates on transistors VT1, VT2, assembled according to the multivibrator circuit, loaded on the primary winding of the step-up transformer T1. In this case, an alternating voltage of 50 ... 60 V is induced on the secondary winding of the transformer, which is rectified by the VD3 diode and charges the capacitor C4. The second conversion stage, which includes the VS1 dinistor and the T2 step-up transformer with the E1 spark gap in the secondary winding circuit, works in the same way as a similar network lighter assembly. Diodes VD1, VD2 form a half-wave rectifier, periodically used to recharge the battery. Capacitor C1 dampens the excess voltage of the network. Plug X1 is mounted on the body of the lighter. The circuit board of this version of the lighter is shown in fig. 4.
The magnetic circuit of the high-voltage transformer T2 is a ferrite ring 2000 NM or 2000NN with an outer diameter of 32 mm. The ring is carefully broken in half, the parts are wrapped with two layers of insulating tape, and 1200 turns of wire PEV-2 0,05-0,08 are wound on each of them in bulk. Then the ring is glued with BF-2 or "Moment" glue, the halves of the secondary winding are connected in series, wrapped with two layers of insulating tape and the primary winding is wound over it - 8 turns of wire PEV-2 0,6-0,8 (Fig. 5).
Transformer T1 is made on a ring of the same ferrite as the magnetic circuit of transformer T2, but with an outer diameter of 15...20 mm. The manufacturing technology is the same. Its primary winding, which is wound second, contains 25 turns of wire PEV-2 0,2-0,3, the secondary - 500 turns of PEV-2 0,08-0,1. Transistor VT1 can be KT502A-KT502E, KT361A-KT361D; VT2 - KT503A - KT503E. Diodes VD1 and VD2 - any rectifier with a permissible reverse voltage of at least 300 V. Capacitor C1 - MBM or K73, C2 and C4 - K50-6 or K53-1, C3 - KLS, KM, KD. The turn-on voltage of the used dinistor must be 45 ... 50 V. The design of the arrester is exactly the same as that of a mains lighter. The establishment of this version of the electronic "match" comes down mainly to a thorough check of the installation, the design as a whole and the selection of the resistor R2. This resistor must be of such a value that the lighter works stably at a voltage of the battery supplying it from 0,9 to 1,3 V. It is convenient to control the degree of battery discharge by the frequency of sparking in the spark gap. As soon as it drops to 2 ... 3 Hz, this will be a signal that the battery needs to be recharged. In this case, the plug X1 of the lighter must be connected to the mains for 6...8 hours. When using a lighter, its spark gap must be removed from the flame immediately after the gas has ignited - this will extend the life of the spark gap.
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