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XEROX ON EACH TABLE

XEROX ON EACH TABLE


Judging by the ads in the newspapers, their choice is the richest, only prices are astronomical. Only a rich organization can afford it. And if you can still build the computer yourself, you only have to dream of a copier. However, there is a way out! Anyone who is familiar with radio technology and photography, in a day or two, can collect a copying device, though not so perfect, but workable.


Xerography appeared several decades ago at the junction between photographic and electrostatics. It turned out that when an exposed paper is exposed , the charge configuration accurately follows the contours of the image, and its density depends on the intensity of the halftones. Spatter on such a sheet of paint, it will stick to electrified areas, and you have an exact copy of the image.

Installation, working on this principle, we propose to do. You will need a high constant voltage source to electrify the photosensitive material, photosensitive paper and the developer with the paint.

Let's start with the preform of the photosensitive material. It is paper coated with a photoconductive emulsion. It is obtained by mixing 2 parts by weight of dry zinc white and one part of BF-2 glue. Thoroughly mix the mass by periodically adding alcohol. It should turn out to be similar in density to sour cream. Now the emulsion is slightly heated. It will become less viscous and it will fit well on the leaf. Paper should be better coated and coated with a thin layer of emulsion with a brush or roller. After letting the sheets dry for about 20 minutes, cover them with a second spoon. After drying at room temperature (about 2 hours), the paper is ready for photocopying. But while she is not susceptible to light.

The surface layer of the photo-semiconductor must be informed of the electric charge. They do this in the dark, using an electrifier-electrode in the form of a metal (copper, brass) disk with a dielectric handle. The appearance of the electrifier and the installation is shown in the figure.

It consists of a dielectric base made of getinax, textolite or vinplast 5-6 mm thick. It is fastened with a copper or brass plate thick 0.5 mm , the size of a typewritten sheet of paper. To avoid accidental contact and short-circuits between the paper and the plate, we lay a layer of dielectric thickness 0.5 mm from fluoroplastic film, thin getinax or textolite. For convenience, it can be fixed to the glue. Metal screws for assembly should not be used, since there is a risk of high voltage breakdown.

The electrode-electrifier is connected to the negative charge, and the plate on the base is connected to the positive pole of the converter. Pay special attention to the electrical insulation of current-carrying buses to the places of their attachment to the electrodes. MGHV wire for this purpose is not suitable, you need a wire type VMMA, MPI, and you can use a cable type RK-75, after removing the shielding from it. After switching on the high voltage source, swipe across the entire surface of the sheet. The paper is now ready for exposure. You can not bear it. Having prepared several sheets, start copying, otherwise the charge can "expire" and the material will lose photosensitivity.

To get a print on paper, you need to project the image. It is not difficult to do this with the help of a photo intensifier, or even better with an epidiaskcope. But remember that in xerography the process corresponds to the formula "positive-positive".

Exposure time at a light source with a power of 100-150 W from a distance 0.5 m from 0.5 to 5 seconds. The best results are given by mercury-quartz lamps, but you can use the usual ones for photos.

Now the line of manifestation has approached. You can apply dry or wet methods. But, of course, at home, the second is more convenient. Dilute thick ink for rotary machines in refined aviation or automotive gasoline in the proportion of 5 grams of paint on 1 l gasoline. It is enough to lower the exposed sheet of paper into this solution, and after a minute the imprint will appear. He does not require fastenings, gasoline will quickly evaporate, and the paint will be firmly held on the surface. So you can get an image not only on paper, but also on glass and even ceramics. The most difficult part of a homemade Xerox is a source of high voltage. Let us dwell on it in more detail.

The design of the converter must be capable of providing a voltage of 10-15 kV at a very low current. The simplest diagram of such a device is shown in the figure. The high-voltage source shown in the diagram consists of a step-down network transformer . with a diode bridge, a converter and a voltage multiplier.

The rectified voltage from the network transformer Tp 1 is fed to the input of the self-excited transducer, assembled in a push-pull circuit with P210 type transistors. Their collector terminals are connected to the winding I, and the terminals of the 6-phase are connected to the winding II . Resistor P 1 and capacitor C 2 provide the necessary mode of operation.

On the winding I leads, an alternating voltage of 3000-4000 Hz appears. It is raised hundreds of times by the secondary winding of the IRS and is fed to a multiplication circuit consisting of high-voltage diodes KC106G and capacitors of the filter type K73-13 with the capacity of 2200 pF and designed for a voltage of not less than 12 kV. The rectified voltage is applied to the photocopying unit.

The step-up transformer Tr 2 is wound on a ferrite core from a television line transformer (TVS-A, TVS-B, TVS-110) consisting of two halves (see Fig.). The high-voltage winding III is wound on a frame laminated of fiberglass, electrocardboard or Plexiglas thick 1 mm . The width of the frame must be at least 30 mm . The winding contains 8000 turns of PELSHO wire with a diameter of 0.08- 0.1 mm . You can use the cable LEL, SEW.

Winding make a turn to the turn, isolating with thin fluoroplastic film or lacotte each layer. Make sure that the coils of the upper layers do not touch the lower ones .

For primary windings, make a sleeve made of cardboard. Winding I contains 14 turns of PEL 0.6 wire, and winding II - 6 turns of the same wire with a tap from the middle. It is desirable to coat the windings with paraffin and wrap the tape .

In the frames, insert the core halves and tighten them with the fastener from the line transformer.

The step-up transformer can also be wound on a conventional iron core type Ш-20 with the thickness of the set 30 mm . The general framework is made of cardboard, getinax or textolite. First, the windings I and II are winded (respectively 20 turns of PEL 1.2 and 16 turns of PEL 0.5 - both with a branch from the middle) and covered with paraffin, and the top is covered with a layer of insulating tape with a thickness 1 mm . Then the winding III - 7000-8000 turns PELSHO 0.1 is wound. It is also impregnated with paraffin.

Transistors should preferably be installed on heat sinks with an area of ​​60-100 square meters. cm from sheet duralumin or brass with a thickness of 1.5-2.0 mm.

The details of the transducer are placed on a 3-5 mm thick getinax board and an insert of the case made of Plexiglas. When installing, pay special attention to the connection between the diodes and capacitors. The connecting wires must be short, and the soldering should be smooth and smooth. All sharp edges of the soldering and protruding ends of the conductors are carefully rounded with a nafile, otherwise they will become a source of corona discharges.

The rectifier is assembled on a bridge circuit using diodes of the type D3O3-D3O5 or similar. The rectified voltage is filtered by capacitor Ц 1 . The alternating voltage is removed from the secondary winding of the step-down transformer Tp1. The primary winding is rated at 220 V. The rectifier is turned on by the toggle switch B 1 .

Network transformer Tr 1 is wound on a core of iron Sh-20 at the thickness of the set 30 mm . The winding I for the 220 V network contains 2200 turns of the PEV-2 wire 0.25; The winding II is wound with a PEV-2 wire with a diameter 1.2 mm and contains 120 turns. For a more accurate selection of voltage, it is advisable to make bends from 90, 100 and 110 turns. Suitable and any ready-made transformer, providing a voltage of 10-12 V at a current of 2 A.

Rectifier and converter should be placed in a common housing. Pay special attention to the insulation of high-voltage terminals, from which high voltage is removed.

Verification and adjustment are reduced to several operations. First check the rectifier. Instead of a transducer, connect a 10 Ohm resistor with a power of 20-25 W of type PEV or C5-35. Plug into the network and measure the voltage on the resistor - it must be at least 10 V.

Then connect the converter to the rectifier. If its circuit is assembled correctly, and the parts are in good order, a thin squeak of the high-voltage transformer will be heard. No - swap out the end leads of winding I or II . If there is a sudden peep or clicks of the breakdown, lower the supply voltage by soldering the rectifier to the secondary winding of the transformer Tp 1 with a lower voltage.

Make sure there are no corona discharges. Turn off the light in the room and take a look at the high-voltage part of the device. If purple flashes appear on the parts' conclusions, this is a sign of coronation . Its indispensable companion is the smell of ozone. Switch off the installation, inspect the soldering points, round off or disintegrate again.

Work on a photocopying machine requires special attention. High voltage is not dangerous in itself. The strength of the current is decisive. As is known, a current exceeding 30 μA is hazardous to life. But this does not mean that you can even accidentally touch current-carrying conductors. You will get a tangible shot spark spark!

And so the advice - with any piping in the circuit, always short - circuit the high-voltage multiplier wire to grounded output of winding III . All re-soldering during installation, conduct with the rectifier turned off from the network.