Copier with fluorescent lamps. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Copier with fluorescent lamps. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Lighting

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In some cases, it is required to light more than one fluorescent lamp (LDS), but several low-power lamps at once. Figure 1 shows the placement of 20-watt LDSs in a blueprint copy machine.

This device (negligent students call it "sdiroscope") allows you to copy to the light drawings the size of a large sheet of Whatman paper in format up to A0 (N44). The sides of the box of the apparatus are assembled from plywood or boards 12 ... 15 mm thick, and its bottom is made from 5-, 8- or 10-mm plywood. From above, the apparatus is covered with sheet plexiglass (plexiglass) 5 mm thick (glass is conventionally not shown in Fig. 1). For a better reflection of light from the inside, the box is lined with aluminum foil or white paper - the same Whatman paper).

Note that it is much more preferable to use not ordinary incandescent lamps in a copier, but LDS. On the one hand, the latter are noticeably more economical and are not afraid of shaking, on the other hand, they give significantly less heating of the Plexiglas cover sheet. This means that the LDS machine will not burn the draftsman's hands and will not require periodic shutdowns to cool down.

To ignite four 20-watt LDS, in the standard version, you will need either four 1UBI-20/220 chokes, or two 2UBI-20/220 chokes and four starters for them. If there are no such chokes, it is permissible to connect the lamps according to a non-standard scheme shown in Fig. 2.

Instead of current-limiting chokes, two transformers T1 and T2 are used, which can be used as vertical scan output transformers (TVK), kinescope incandescent transformers or audio frequency output transformers (TVZ) from an old tube TV. For example, such "personnel officers" as TVK70L2, TVK-110LM, TVK-110L-1, TVK-110-L2 are suitable. Their low-voltage secondary winding wound with the thickest wire (terminals 3 and 4 of the transformer) is connected as winding I, and the highest-voltage winding (terminals 1 and 2) is connected as winding II. At the "filament" winding I will be the winding (relatively low-resistance) of the kinescope filament power supply, and at the "output" the power winding of the dynamic head.

Excessive alternating voltage on winding I of transformers T1 and T2 is "quenched" by a high-voltage paper capacitor C1 with a capacity of 10 .... 25 microfarads. The most suitable capacitors are MBGCH-1 or MBGCH-2 with a rated voltage of 500 V or KBG-MN (KBG-MP), but with a rated voltage of 1000 V. Any other capacitors specially designed for operation in an AC voltage network of 220 V are also suitable. Thus, transformers T1 and T2 are actually connected as current transformers, not voltage ones.

Resistor R1 with a resistance of 200 ... 750 kOhm and a dissipation power of at least 0,5 W allows you to quickly discharge the capacitor C1 after disconnecting the device from the network, thereby almost instantly reducing the voltage on the plug to a safe level. Three-position switches SA1 and SA2 (toggle switches with a middle position, for example, type VTZ) can turn off any of the lamps: EL1 or EL2 and EL3 or EL4, if required by the conditions of work on the copier. Switches (ordinary toggle switches) SA3 and SA4 allow you to turn off (by closing the winding I of the transformer T1 or T2), respectively, a group of lamps EL1, EL2 or EL3, EL4. The brightness of the glow of burning lamps (from among EL1-EL4) practically does not change.

Temporarily turning off some lamps can facilitate the ignition of other lamps if they have partially lost their ability to light up easily over time (gas-filled lamp starters are not used in the same way as lamp filaments, which may be burnt out). It is interesting that, unlike the typical circuit, the ignition of the LDS with this method of switching on occurs almost instantly and silently. If it is not supposed to turn off certain lamps during operation on the device, the SA1-SA4 switches can be omitted.

The uniformity of illumination of the entire field of the drawing can be significantly improved by increasing the number of lamps from four to six. Then the dimensions of 150 and 300 mm (Fig. 1) are reduced to 100 and 200 mm, respectively. In addition, in this case, another transformer is needed, the I winding of which should be connected in series with the I winding of transformers T1 and T2. The total number of transformers can be five or six or even more.

If there are no "short" 20-watt (or 18-watt) lamps, two or three larger 40-watt (or 36-watt) lamps can be installed in the copier. Then each of them is connected to winding II of transformers T1 and T2 instead of series groups of lamps EL1, EL2 and EL3, EL4. More "long" 40-watt lamps are placed along the apparatus.

The required capacity of the quenching capacitor C1 (or a bank of capacitors connected in parallel) depends on the specific transformers that you have at hand. In any case, this capacity is chosen as the minimum necessary.

If you do not have high voltage capacitors, you can replace them with a 220-volt lamp (or lamps connected in parallel). Note that in terms of AC resistance, a 150-watt lamp is equivalent to a capacitance of 10 microfarads, a 200-watt lamp is equivalent to a capacitance of 13 microfarads, a 300-watt lamp is equivalent to a capacitance of 20 microfarads, and a 400-watt lamp is equivalent to a capacitance of 26 microfarads. It should be remembered that, unlike a capacitor (essentially a "wattless" resistance), an incandescent lamp will waste significant electricity. Discharge resistor R1 with an incandescent lamp, of course, is not needed.

Replacing the capacitor C1 with a suitable inductor is also suitable. So, two chokes 2UBI-20/220 connected in parallel are equivalent to a capacitance of 12 μF, one choke 1UBI-80/220 or two 1UBI40/220 connected in parallel is 14 μF, a parallel combination of 2UBI-20/220 and 1UBI-80 / 220 (or 1UBI40/220 and 1UBI-80/220) - about 20 microfarads, 2UBI-20/220 and 1UBI100/220 (or 1UBI-40/220 and 1UBI-100/220) - about 24 microfarads, and 1UBI-80 /220 (2 pieces in parallel) - 28 microfarads. Resistor R1 with a choke is also not needed, and the loss of electricity is noticeably less than with incandescent lamps.

Author: V. Bannikov

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