The design of absolutely any device, especially if it (the device) includes both electronic and mechanical elements, may seem to an uninformed person to be a storehouse of secrets and mysteries, in which oh, how difficult it is to understand yourself. Flatbed scanners are just such an option. At first glance, the scanner device does not seem particularly complicated: a case with a few connectors and a couple of buttons, a removable tablet cover, and glass on which the originals are placed for scanning. But this is how the "economy" works, and what the numbers of its specification mean - this is, as they say, a completely different song. To learn how to navigate the numerous models of scanners on the computer market today, you need to imagine the real value of the characteristics indicated by manufacturers. But in order to make this article more informative, let us examine the design of the scanner, as they say, in the literal sense of the word “disassemble”.
Let's start with the most important element of any scanner - a light-sensitive matrix, which is, as it were, its "eyes".

The matrix

Yes. The matrix is \u200b\u200bthe most important part of any scanner. The matrix transforms changes in color and brightness of the received light flux into analog electrical signals that will be understandable only to its only electronic friend - an analog-to-digital converter (ADC). From this point of view, the ADC can be compared to a guide-translator, its constant companion. Only he, like no one else, understands the matrix, because no processors or controllers will parse its analog signals without preliminary interpretation by the converter. Only he is able to provide work for all his digital colleagues who perceive only one language - the language of zeros and ones. On the other hand, you can take any processor, converter or amplifier, illuminate them with the brightest light source and wait for any reaction until you get bored. The result is known in advance - it will be zero, because no other electronic components of the scanner are sensitive to it. If you like, they are all blind from birth. The matrix is \u200b\u200banother matter. The light flux, falling on its surface, literally knocks out electrons from its sensitive cells. And the brighter the light, the more electrons will be in the storage rings of the matrix, the greater their strength will be when they rush to the exit in a continuous stream. However, the current strength of electrons is so incommensurably small that even the most sensitive ADC is unlikely to "hear" them. That is why an amplifier awaits them at the exit from the matrix, which can be compared with a huge horn that turns, figuratively speaking, even a mosquito squeak into the howl of a loud siren. Amplified signal (still analog) will "weigh" the converter, and assign each electron a digital value, according to its current strength. And then ... Then the electrons will represent digital information, which will be processed by other specialists. Image reconstruction work no longer requires the help of a matrix.
But let's leave the general reasoning. Let's look at the practical side of things. Most modern home and office scanners are based on two types of matrices: CCD (Charge Coupled Device) or CIS (Contact Image Sensor). This fact gives rise to two questions in the minds of users: what is the difference and which is better? If the difference is noticeable even with the naked eye - the body of a CIS scanner is flat, in comparison with a similar CCD device (its height is usually about 40-50 mm), then it is much more difficult to answer the second question. The answer here needs to be reasoned in order to avoid an avalanche of generated questions like "why is it better?", "Why is it better?"
First, let's look at the main advantages and disadvantages of these two classes of scanners. For convenience, I have compiled them into a small table:


The CCD scanner has a greater depth of field than its CIS counterpart. This is achieved through the use of a lens and a system of mirrors in its construction.

In the figure, for ease of perception, only one mirror is drawn,
whereas a typical scanner has at least three or four

CCD scanners are much more common than CIS scanners. This can be explained by the fact that scanners in most cases are purchased not only for digitizing sheet text documentsbut also for scanning photographs and color images. In this regard, the user wants to get a scan with the most accurate and reliable color reproduction, and in terms of light sensitivity, the CCD scanner transmits color shades, highlights and halftones much more strictly than the CIS scanner. Note that the error in the spread of the levels of color shades, distinguished by standard CCD scanners, is about ± 20%, while in CIS devices this error is already ± 40%.

Schematic representation of a CIS sensor

The CIS-matrix consists of an LED bar that illuminates the surface of the scanned original, self-focusing microlenses and the sensors themselves. The sensor design is very compact, so a scanner that uses a contact sensor will always be much thinner than its CCD counterpart. Besides, such devices are famous for their low power consumption; they are practically insensitive to mechanical stress. However, CIS scanners are somewhat limited in their use: devices, as a rule, are not adapted to work with slide modules and automatic document feeders.
Due to the peculiarities of the technology, the CIS-matrix has a relatively small depth of field. For comparison, CCD scanners have a depth of field of ± 30 mm, and CIS - ± 3 mm. In other words, if you put a thick book on the flatbed of such a scanner, you will get a scan with a blurred line in the middle, i.e. where the original is not in contact with the glass. With a CCD, the whole picture will be sharp because it has a mirror system and a focusing lens. In turn, it is the rather bulky optical system that does not allow the CCD scanner to reach the same compact dimensions as the CIS counterpart. However, on the other hand, it is the optics that provide an obvious gain in quality. Note that the requirements for optics are very high, so the rumors that some models of scanners are used, de, "plastic mirrors" are greatly exaggerated, if not "fictional". ;)
In terms of resolution, CIS scanners are also not a competitor to CCDs. Already, some models of CCD scanners for home and office have an optical resolution of about 3200 dpi, while CIS devices have a limited optical resolution, if I am not mistaken, so far 1200 dpi. But, in general, it is not worth dumping CIS technology from shields. All technologies are developing rapidly. Scanners with a CIS-matrix have found their application where it is required to digitize not books, but sheet originals. The fact that these scanners are powered entirely via USB and do not need an additional power source came in handy for laptop owners. They can digitize the original and translate it into a text file anywhere, without being tied to the proximity of electrical networks, which allows them to close their eyes to a number of shortcomings of the contact sensor. Actually, therefore, the answer to the question "which scanner is better" can be based on your specific requests.

The most important element of the scanner is the CCD matrix

In the above photo, you see a CCD that appears to be a "large chip" with a glass window. This is where the light reflected from the original is focused. The matrix does not stop working all the time while the carriage with a scanning carriage, driven by a stepper motor, makes its way from the beginning of the tablet to its end. Note that the total distance the carriage moves in the "Y" direction is called the sampling rate or the mechanical resolution of the scanner (we'll talk about this a little later). In one step, the matrix completely captures the horizontal line of the tablet, which is called the raster line. After the expiration of time sufficient to process one such line, the carriage of the scanning unit moves a small step, and it is the turn to scan the next line, etc.

CCD side view

In the side view, you can see two ordinary screws that perform a "delicate" role. With their help, at the stage of assembling the scanner, the matrix was precisely aligned (also note the U-shaped slots in the printed circuit board in the top view) so that the reflected the light from the mirrors would fall evenly over its entire surface.By the way, if one of the elements of the optical system is skewed, the computer-generated image will turn out to be "striped".

An enlarged image of a part of the CCD (macro
produced by Canon EOS D60 digital camera)

The enlarged photo of the CCD-matrix clearly shows that the CCD-matrix is \u200b\u200bequipped with its own RGB filter. It is he who is the main element of the color separation system, which many people talk about, but few people know how it actually works. Typically, many reviewers confine themselves to the standard wording: "A standard flatbed scanner uses a light source, a color separation system, and a charge-coupled device (CCD) to collect optical information about the object being scanned." In fact, the light can be separated into its color components and then focused on the matrix filters. An equally important element of the color separation system is the scanner lens.

The scanner lens is actually not as large as it appears on
photos

Housing

The body of the scanner must be rigid enough to avoid possible distortions in the structure. It is certainly best if the base of the scanner is a metal chassis. However, most home and office scanners available today are entirely made of plastic to keep costs down. In this case, stiffening ribs, which can be compared with ribs and spars of an aircraft, give the required structural strength.

Location of the main functional units of the scanner

An important element of the body is a transport lock, the presence of which is designed to protect the scanning carriage from damage during transportation of the scanner. It must be remembered that before turning on any scanner equipped with such a lock, it must be unlocked. Otherwise, the mechanisms of the device can be damaged. In principle, manufacturers draw the attention of buyers to this small nuance with bright stickers with appropriate warnings.
Some people believe that the corpus has nothing to do with the quality of the scan. However, this is not the case. The fact is that the optical system of the scanner does not tolerate dust, so the body of the device must be sealed, without any cracks (even technological ones). More than once I came across models that did not meet such requirements. If you are about to buy a scanner, then I would recommend paying attention to this.
Also, when buying a scanner, pay attention to the possibility of separating the tablet cover. This feature of the machine is especially useful when scanning originals such as thick books or magazines.
The edges of the tablet should have a gentle slope - this makes it easier to quickly remove the original from the glass. In addition, there should be no gap between the glass and the document plate that would prevent the original from being removed. Also pay attention to the presence of markings around the perimeter of the tablet.

Control block

All scanners are controlled from the personal computer to which they are connected, and required settings before scanning are set in the user window of the control program. For this reason, home and office scanners do not need to have their own control box. However, many manufacturers go to meet the most unprepared users and install (usually on the front panel) several "quick scan" buttons.

Quick Scan Buttons - An Element You Can Do Without

In the photo above, you can see that each button has a specific icon. Typical quick start functions usually involve starting a standard scan operation, with output to a printer, and then sending to e-mail, by fax, etc. It is clear that specific parameters of the scan quality are set for this or that button. However, pressing this or that button first leads to the launch of the application on the computer (if there are several), which is responsible for the called operation. Note that not all SOHO scanners are equipped with their own control unit, and such elements are even absent in professional devices.
Some manufacturers “sin” by excluding a number of settings from the scanner driver, which, in their opinion, are not used by most ordinary users. For example, Hewlett-Packard SOHO scanners lack the ability to change gamma correction, load ICC profiles and much more. But it is Hewlett-Packard who, like no one else, likes to "pamper" users with a number of quick scan buttons.

About light sources

Absolutely every scanner uses its own illuminator. This is the name of a small and powerful module whose task is to turn on and off the scanner lamp (or whatever replaces this lamp). In CIS scanners, an LED line is used as light sources, due to which this class of devices consumes so little energy.
In CCD scanners, originals are normally illuminated by a cold cathode fluorescent lamp. Its light is thousands of times brighter than LEDs. But in order to cause the gas inside the lamp to glow, a very high voltage must be applied to its input. It is generated by a separate unit called an inverter.

A high voltage module is required to power the lamp

The inverter raises the voltage from five volts to several kilovolts, and also converts DC to AC.

In general, there are three main types of lamps used in scanners:

xenon gas discharge lamp (Xenon Gas Discharge);
hot cathode fluorescent lamp;
cold cathode fluorescent lamp

However, home and office scanners use only cold cathode lamps for a number of reasons.

Cold cathode lamp

The scanner lamp is mounted on the plastic chassis of the scanning carriage directly above the reflector. The reflector itself has the form of a reflector (effective "collector" and reflector of light) in the form of a magnifying mirror. The light from it is amplified to brighten the subject on the tablet. After reflecting from the original on the glass, the light passes through the slit of the chassis (in the photo I highlighted its contour in blue) and is received by the first, longest mirror of the optical system.
Among the obvious advantages of a cold cathode lamp is the long service life of 5,000 - 10,000 hours. For this reason, by the way, some scanners do not use switching off the lamp after the scan is complete. In addition, the lamps do not require any additional cooling and are very cheap to manufacture. Of the shortcomings, I note a very slow inclusion. Typical lamp warm-up times range from 30 seconds to several minutes.
The lamp has an important effect on the scan result. Even with a slight deviation of the characteristics of the light source, the luminous flux incident on the receiving matrix also changes. This is partly why it takes such a long time to warm up the lamp before scanning. Note that some drivers allow you to reduce the warm-up time if the quality of digitizing is not so important (for example, when scanning text information). I will add, in order to somehow compensate for the loss of lamp characteristics (and this inevitably happens during long-term operation of the device), scanners automatically perform a self-calibration procedure using a black and white target located inside the body.

The photo clearly shows how under the influence of light with the flow
time, the case plastic and the calibration target fade

The scanner under study is no exception. The above photo clearly shows the color target, according to which the scanner adjusts the colors before scanning, compensating for the "aging" of the lamp. It can also be seen here that with the passage of time, not only the inner plastic, which is permanently illuminated by the lamp, fades, but also the calibration target itself. This, in turn, leads to color drift and increased color distortion.

A cold cathode lamp is somewhat similar to a fluorescent lamp.
light ... just a little


If desired, from the inverter and the cold cathode lamp, you can
build a table lamp

In the photo you see the misuse of the scanner lamp. ;) The inverter module was connected to a standard computer power supply, for which wiring with an adapter was soldered to its board. In principle, if you fit a holder here, you will get a pretty good and bright table lamp.

ADC operation

Who helps the scanner processor "find common ground" with the matrix? Of course, an analog-to-digital converter, which converts analog signals into digital form. This interesting process can be represented as follows. First, the ADC "weighs" the input voltage, reminding a store clerk picking up a set of standard weights of the same weight as the product. Then, when the voltage is measured, the ADC presents the data to its "boss", that is, the processor, but already in the form of numbers. And as a result, everyone is happy.
You can imagine yourself in the role of a processor and ask what happens at the ADC output when the input voltage is changed? Let's supply, for example, 4 Volts to the input of the converter, then 9 Volts. At its output, the following variations of numbers will appear: first 00000100, then 00001001. In binary code, these are numbers 4 and 9. The number of zeros and ones with which the ADC expresses the measured value is its capacity, which is measured in bits. A parameter such as digit capacity of the converter is extremely important for the scanner, because it characterizes the accuracy of the measurement of the input signal.
Today, inexpensive scanners can be seen on store shelves, in which converters with a bit depth of 24 to 48 bits work. In theory, it is always better to choose a scanner that has more bit depth. In this case, one subtlety should be taken into account: sometimes manufacturers write "48 bit" in large letters on boxes, and somewhere in the corner they specify in small print: "software 48 bit, hardware 36 bit". This means that the big beautiful number has nothing to do with the accuracy of the ADC set in the scanner, and the real bit depth in this case is 36 bits. It is on her that you should be guided. It should be admitted that in home practice the differences between the results of 36- and 42-bit scanners are almost imperceptible (the human eye is able to distinguish about 24 bits of color shades, i.e. about 16.7 million). In our case, the bit depth of the converter and the color depth are one and the same. After all, the converter calculates nothing more than the colors of the points from which the image is composed. The greater the bit depth of the converter, the more faithfully the scanner can reproduce the color of each point in the image. Accordingly, the more the image will look like the original.

CPU

Modern scanners are equipped with specialized processors. The tasks of such a processor include coordinating the actions of all circuits and nodes, as well as generating image data for transmission to a personal computer. In some models of scanners, the processor is also assigned the functions of the interface controller.
List program instructions for the processor is stored in a read-only memory chip. The data is written to this microcircuit by the manufacturer of the scanner during the production phase. The contents of the microcircuit are called "firmware" or "firmware". Some professional scanners offer the option to upgrade, but inexpensive home and office scanners usually don't.
In addition to the read-only memory microcircuit, the scanners also use random access memory, which plays the role of a buffer (its typical values \u200b\u200bare 1 or 2 MB). The scanned information is sent here, which is almost immediately transferred to the PC. After sending the content from memory to the personal computer, the processor zeroes the buffer to form a new message. Note that instructions for the processor are also recorded in the cells of the RAM, but already the processor itself (for this, it is equipped with several kilobytes of its own "RAM"). The organization of his memory is built on the principle of a pipeline, i.e. after executing the first instruction in the queue, its place is taken by the second, and the place of the last - new instruction.
The amount of RAM of the scanner was previously indicated by the manufacturers in the technical specifications of the scanners. However, since this parameter practically does not affect the speed of the device; it is often silent on modern scanners. It is also kept silent if a particular scanner uses a certain area of \u200b\u200bthe computer's RAM, which is implemented by means of the driver.

Interface controller

The interface controller is responsible for the exchange of information and commands between the scanner and the computer. As I noted above, this microcircuit may be absent if the processor has an integrated controller module. In the era of "doubles" and "three-rugs" scanners were produced with SCSI, IEEE1284 (LPT) and even RS-232 interfaces. Today's range of SOHO scanners is limited to USB, FireWire and SCSI interfaces. At one time, there were rumors about the appearance of Bluetooth scanners, but so far it has not gone beyond rumors. It is quite obvious that in devices with different interfaces installed the same different controllers. They are not compatible with each other, because they "speak different languages."

In our case, the interface board combines SCSI and USB ports, as well as
has two slots for connecting additional modules

SCSI (Small Computer Systems Interface)

SCSI scanners were the most common a few years ago. It must be admitted that the era of SCSI scanners is coming (or has already come) to an end. The main reason is the emergence of high-speed uSB interfaces and FireWire, which require neither special delicacy when connecting, nor additional adapters. Among the advantages of the SCSI interface are its high bandwidth, as well as the ability to connect up to seven different devices on one bus. The main disadvantages of SCSI are the high cost of organizing the interface and the need to use an additional controller.

USB (Universal Serial Bus)

The USB interface is the most widespread due to its integration into all modern motherboards as the main connector for peripheral devices. Today, the vast majority of home scanners come with a USB interface. In addition, the group of CIS scanners receives the necessary power through the USB port, which attracts laptop owners. Agree, this quality cannot be realized through SCSI.

FireWire (IEEE1394)

When choosing a connection type, at least for me, the FireWire interface is preferable. FireWire is a high-speed serial I / O interface that differs from USB themesthat it does not require a host controller to provide connection. Its work is organized according to the peer-to-peer scheme. Actually due to this, a lower (in comparison with USB) load is achieved central processing unit.
Soon, peripheral devices with a new modification of this interface - FireWire 800 (IEEE1394b) will see the light. This is when it will become the fastest peripheral standard ever developed.

Broaching mechanism

The main movable module of the scanner is its scanning carriage. It includes an optical unit with a lens and mirror system, a photosensitive matrix, a cold cathode lamp (if it is a CCD scanner) and an inverter board. A toothed stretching belt is rigidly fixed to the scanning carriage, which drives the stepper motor of the apparatus.

Attachment of the belt to the scanning carriage



Elements of the broaching mechanism

A special tension spring is responsible for the tight contact of the belt with the gears, which is put directly on it. The carriage with a scanning carriage moves along the guide slide along the body of the apparatus (see photo).

Engine

Stepper motor

The Step Motor can turn the spindle in both directions in very small steps. Because of this feature, it is always possible to move the scanner carriage to a strictly defined distance. This engine is found in every flatbed scanner. It rotates the gearbox (the gears that you see in the photo) and drives the carriage, which contains the optical unit, lamp, and matrix. A special microcircuit is responsible for the choice of the direction and speed of rotation - the motor controller. The accuracy of the carriage movement is called the mechanical resolution in the "Y" (Y-direction).

The optical resolution of the scanner is the X direction, and its
mechanical resolution - Y direction

In general, optical resolution is determined by the number of elements of the matrix line divided by the width of the working area. Mechanical - the number of steps of the scanning carriage in the direction of movement Y. In the specifications for scanners, you can find designations such as "600x1200". Here the second number is the mechanical resolution, while the first characterizes the optical resolution of the scanner. There is also an interpolated resolution, which is sometimes several orders of magnitude greater than the optical resolution, but does not depend in any way on the physical equipment of the apparatus. I would call it "zoom resolution". The interpolation functions (enlarging the original image) are performed by the scanner software. The value of the manufacturer-specified interpolation values \u200b\u200bis questionable - any image can just as well be enlarged using Photoshop.

Engine insides



Reducer

The motor core is connected on the outside by a gear train, which is the simplest gearbox. Its large gear and stretches the strap to which the scanning carriage is attached.

Power Supply

Scanner power supply

Home or office scanners do not consume too much power from the mains, so there are no powerful elements in the power supplies of SOHO devices. The internal power supply unit of the device considered in this article produces voltages of 24 Volts / 0.69 A, 12 Volts / 0.15 A and 5 Volts / 1 A. for a light source - a lamp with a cold cathode, a high voltage of several kilovolts is required, a separate unit is responsible for its power supply, which I talked about a little higher.

Additional devices

Many flatbed scanners have an accompanying accessory, in most cases purchased separately. These include the automatic document feeder and the adapter for scanning transparent originals (slide adapter).

The ADF scanner is bulky
construction

An automatic paper feeder is required when you have to scan many standard-size print sheets. Making sure the ADF can be connected to your scanner is easy enough. To do this, you can simply look at the connections panel and make sure there is an ADF (Automatic Document Feeder) jack. It should be noted that the automatic document feeder is always "tied" to a specific scanner model or series of models. There is no multi-purpose feeder! The reason is that this device controlled from the scanner interface board. It is clear that the work of the feeder is impossible if there is no communication with the scanner, so when buying, be careful and make sure that your scanner supports work with a specific ADF.

View of the transparent window of the automatic document feeder from the other
glass sides

The ADF works as follows. After the auto-calibration and readiness check phase, the scanner positions the carriage in front of the ADF transparent window. Then, sheet originals are taken one by one from its input tray, and when they pass through the designated window, they are digitized.
The Slide Adapter is an optional accessory for digitizing transparent originals (transparencies, slides, and negatives). There are two types of such adapters: passive, which uses a scanner lamp, and active, translucent transparent original with its own lamp.
The active slide adapter has its own light source that shines through the transparent original. Some models of these slide adapters have a movable carriage with a light source, which is driven by a motor and a broaching mechanism. The light source moves along the rail according to the positioning of the scanner carriage. This turns off the scanner's own lamp. Today, the more common models of scanners for home and office are without moving parts in the slide adapter module. A typical example is EPSON Perfection 3200 Photo, recently tested by our test laboratory. Its light source is built into the scanner cover and occupies its entire usable surface. To match the adapter with the scanner, a wire with a connector comes out of the cover, which connects to a special socket on the back of the device (it is designated by the abbreviation XPA). The adapter lamp is activated automatically when changing the original type in management program, which is additionally signaled by an indicator in the scanner lid. Translucent originals fit into the included templates that support: 35mm film strip of 12 frames, four 35mm slides inserted into frames, 120/220 (6 x 9 cm) / 4 x 5 "" films. Well, the templates themselves are placed on the scanner glass. During scanning, a stream of light passes through a transparent original, and, entering the optical system of the scanner, is processed in the same way (as an opaque original). It is clear that such scanner properties as optical resolution and light depth do not change when using a slide adapter, which cannot be said about the range of optical densities. This parameter of the scanner directly depends on the brightness of the light source and the exposure time. You can imagine it like this: the darker the original, the less light it lets through, the longer it takes for the CCD drives to collect the required amount of charge. The darkest transparent originals are X-ray films (up to 3.6D). To get a high-quality scan from them, you need a bright light source. However, the range of reproducible optical densities of the scanner is by no means determined by the lamp brightness alone. It mainly depends on the bit depth (or accuracy) of the analog-to-digital converter, the quality of the optical system and the capabilities of the photosensitive matrix.
A passive slide module is simpler than an active one. This adapter uses the scanner lamp itself as the light source. In this case, the luminous flux intensity is significantly lower than in the case of an active adapter. Accordingly, the quality of scanned images is lower, which is quite acceptable, for example, for the Web. Passive slide adapters are also inexpensive.

Conclusion

In general, it is possible to talk about the scanner as a complex electronic device for a long time, but still it is impossible to convey all the interesting nuances within the framework of one article. Today we found out the following: for what reasons CCD-scanners digitize originals much better than devices with a contact sensor; why is the bit depth of the converter important, and how does the optical resolution differ from the mechanical one; what kind of light sources are and how they affect the quality of the scan; how the electronic and mechanical parts of the scanner interact, and why slide adapters are not suitable for all devices. In general, I tried to tell you about the features of modern SOHO scanners in the most accessible form possible, and I would be interested to know your opinion about this article.

From kind people I got into my hands such a rather aged scanner, Mustek 6000p, a device from the times of Windows 95 and large white plastic cases. As a rarity, it is not of great value, but it is a pity to throw it away without looking inside).

Actually, all of its electronic content, the body is sent to the trash heap.

The scanning carriage illuminator is a conventional cold cathode fluorescent lamp (CCFL), similar to those used in LCD backlights.

Board from the carriage. On the left side we see a high-voltage inverter, it's time to try to light the lamp.

In the left corner there is a 7812 integrated regulator, designated Q8, it is easy to understand from which paths the inverter receives power. At its input, when the scanner is turned on, about 14 volts, but the lamp does not light up, how to start it? There are not so many tracks leading to the section of the board with the inverter from the connector that connects the carriage board to the main board, so let's assume that a switch is assembled on the Q5 transistor that starts the lamp.

With tweezers, close the resistor R3, connected to the base of the transistor, to + power, and ... let there be light!

Having figured out what's what, cut off all unnecessary, solder the jumper resistor between R3 and the power supply ...

... and pins for the printer's native power connector.

We will get such a neat inverter board, check it again.

To illuminate the workplace, this, of course, is not enough, but you can make a backlight in some box like a lamp in a refrigerator. As a body donor, an equally elderly mouse, the same age as the scanner, came up well. The switch will be a reed switch with normally closed contacts.

Assembled. It is a pity that the buttons do not carry any functional load \u003d)

We attach the lamp and the body to double-sided tape. On the door there is a magnet from the hard drive on the same tape. Not very aesthetically pleasing, but it does the job.

More than enough to illuminate a small space

The attentive reader will notice that in the photo of the board in the mouse case there is already a jumper instead of a stabilizer - it is no longer needed, the inverter is powered by a home server, which is located on the same cabinet.

To begin with, a short introduction.

One day it was time to clean up at work, to clean up the rubble of old boxes from under monitors, printers, cases, etc. And sorting out these rubble, two old fairy scanners UMAX 1200S and, in my opinion, 600S caught my eye.
And the time has come to mock them, as they mocked me in their time.

Having quickly disassembled the first 1200, I took out everything more or less useful from there, namely: a red-hot pin on which the scanner complex with a lamp traveled, a microcircuit and the scanning sensor itself with a mirror system. Taking out all the giblets, I decided to figure out what was valuable there. I don’t know the technology of those years, but the scanning sensor turned out to be gilded in appearance both outside and inside. Gold did not seduce me, the analysis of the scanner continued.
In addition to the mirror systems in the main moving part of the scanner and the lens, there was a lamp very similar to a fluorescent lamp, but only a couple of millimeters thick.

A power circuit was connected to the lamp, from which two wires went off at the connector, which greatly seduced me to connect it to some DC source. Fortunately, in the previous box there were several power supplies from switches, monitors, and fig knows what else.

Having disassembled all the trash and throwing out the excess, I proceeded to the tests.

To begin with, a 5 volt and 2 ampere power supply was chosen. Plugging in the lamp, I saw that it lit up, but not completely. A few cm in the far part of the lamp were dark. It's time for a 9 volt power supply with 2.2 amperes. (the one above)
At the same time, the lamp lit up quite brightly and completely.

Knowing that the scanner was powered by a 12v 2a power supply and knowing the hot temper of the lamp, as well as the fact that it was not intended for permanent operation, I did not select a bp. more power, especially since the brightness was enough for me.

And so, when I came home, I found a use for these lamps - to illuminate the space under the table.

For a long time I was annoyed by the fact that under the table, crawling to the computer, I had to take a flashlight and at the same time there were several problems both with the batteries for it and with the fact that one hand was busy and I had to be distracted, watching where the flashlight was shining. It was decided to hang a lamp under the table, a place was marked and instruments were laid out.

It turned out to be very convenient that the standard lamp reflector from the scanner was removable and with its own mount.

It's time to create a box for the lamp power circuit, so as not to hang it naked and ugly. For this, a 6mm thick poster white plastic and a lower blank-blank from a reel with blanks were taken.

From the tools I needed: a Dremel with a cutting disc, a round file, two small drills (in my case for a hexagon), a paper knife with replaceable blades, a soldering iron and screwdrivers.

From the available one was: a connector for the desired power supply, double-sided tape, two small screws and a long screw with a nut.
Carefully cut off two approximately identical pieces of plastic with a knife and glue them with a small piece of double-sided tape to align them along the edges with Dremel.

Without forgetting to put on goggles and preferably a respirator, we get to work.

I will retreat a little, the glasses are clear for what, but I will explain the purpose of the respirator a little. The fact is that Dremel works with rotation up to 33 thousand revolutions per minute and the dust from working with it turns out to be quite fine. And in order not to inhale the dust, which is incomprehensible of what, you need a respirator

Dirty everything workplace and having made two pieces of plastic the same, proceed to cutting the hole for the power connector using a knife and a pencil.
It is enough to scratch the upper part of the power connector with a pencil, and attach it to the desired place on the plastic - we get an approximate stencil for cutting.
Cutting out, we apply both plastics to the circuit, having previously inserted the power connector. Next, we look at how the main fastening screw will pass through the entire structure, first mark the hole on one side, and, pushing it into the already drilled hole, mark and make the second hole.
Next we take the second plate, where the nut will be. We thread and tighten the screw with the nut on it. Then press the nut into the plastic with a little effort, using a hot soldering iron, until it stops protruding. Cool down and unscrew the screw.
We take both lids of our box and from the inside we make small belts of about a millimeter by millimeter, stiffeners will be inserted there, which are also decorative plugs that cover the edges of the power circuit.
By and large, almost everything is ready, it remains only to make mounts for the lamp itself.

To do this, we take the same white plastic and cut out two small rectangles, make holes with drills, first small, then larger, but the holes should not be exactly in the center. then the mounts will not allow the lamp to rotate; they need to be done with a slight downward displacement. Then we twist with screws and glue double-sided tape on the outer base of the resulting mounting planes.

We insert the lamp connector into its power supply circuit, and the circuit into our self-made box and slowly tighten it, but not completely.
Now we start making the side walls. To do this, mark the cutting place in the already prepared "blank gasket" and cut out the wall in advance of a slightly larger size. We put it on the box and see how it fits. When you like the size, you can make a second wall.
Having attached the finished first wall as a template, we adjust the second one in size.
When everything is ready and all burrs are removed, we proceed to assembly.
We take the power circuit, cut off the connector for external connection power supply and solder our connector for the power supply to it. We reassemble the whole box, having previously isolated all the bare contacts and cleaning all traces of fuss. We twist, and at the end, we insert stiffeners, and then we twist to such a state that the box does not fall apart. If not everything keeps well, you can glue the stiffeners along the edges with additional superglue so that it does not fall apart, neither from falling, nor from hands.

Not everything worked out well for me, namely: the screw was outside the cover, so that it had to be cut down.

Then, on the side of the nut, we glue four small pieces of double-sided tape, so that later you can quickly and easily remove it. I still didn't have a switch button, it will be soldered onto the bp cord. later.

If someone doesn't want to mess around like that (I just needed to understand Dremel's work with different materials), he can find any suitable box and fix the diagram in it.

Who wants to have a backlight in the case, I can advise that to connect to any 12v line with the required resistance.

You can also try to use a lamp without its reflector (besides, it is not really a reflector, but rather an extinguisher, since it is not mirrored, but white and black). But for this you need to be extremely careful about the ends of the lamp, since the wires soldered into the glass are thick enough and they can be broken off, or the glass can crack in these places. There are special rubberized holders on the edges of the lamp, on which I would recommend equipping some of your own fasteners. The lamp worked for about 40 minutes with my bp. practically did not heat up, neither the reflector, nor the elastic bands on the sides of it. If the voltage supplied to the lamp is greater than 9v, then the lamp will most likely overheat and possibly fail. If you decide to use it without a reflector, although it will illuminate everything around it, it will also shine into the eyes, which somehow did not seem enough to me.

I also want to warn about the transformer on the lamp power circuit. I do not know what current it gives out and what it is, but if you bring your finger or other part of the body close to its contacts, an electric arc arises, which, for example, burned out a pattern on my finger. The distance to the contacts can be up to two millimeters.
Shock, of course, will not kill, but you can get a small burn.

So, the finished version ..

Not inferior in efficiency to serious industrial analogues. Now let's move on to the device circuit itself, which is based on the AT89C52 microcontroller.

Explanations for the diagram:

• - JP1 - DMX.
• - JP2 - DMX / music switch.
• - JP3 - microphone (with respect to polarity).
• - JP4 - variable resistor 50-100 kOhm, microphone sensitivity regulator.
• - JP5 - food. I used ~ 10 V to get +14 V to the motors
• - JP6, JP7 - connection of optical sensors for zero position of gobo circles and color. A slot is made in the circles, along which the circle stops.

JP8 - strobo drive control. For me, this output goes to a transistor, which, through an optocoupler and a triac, controls the extinguishing of the lamp. That is, there is no signal - the lamp is off, there is a signal - the lamp is on). Here is the control diagram:

The triac controls the electronic power supply. It was 12V 200W.

I redid it to 15 V and used a lamp with a reflector from medical devices 15 V 150 W. There is a thermistor (NTC1) in series with the lamp so that the lamp lights up smoothly and does not burn out.In the mode from music, this unit does not work and the lamp is constantly on. This board is fixed on a piece of PCB and screwed right under the lamp:

• - JP9 - optical prism control. A slider is installed, which, when the signal at this output, turns and rotates the optical prism, which doubles or upsets the image).
• - JP10 - JP11 - stepper motor connection - 2 mirror controls, gobo circle and color circle.
• - JP12, JP13 - connector for in-circuit programming.

Firmware for MK and source code is possible. Other files are on the forum. Photos of the light scanner board on the microcontroller AT89C52:

The gobo circles and colors are stopped by an optical sensor. The circle spins in the optosensor slot. when the cut in the circle passes through the optocell, it stops. The motors for the position of the mirror, after switching on, deflect it to the extreme position, beat against the stop and stop. Then they turn at a certain angle in the opposite direction - this is the middle position of the mirror.

I bought a gobo circle without dichroic filters. However, I could not use the ready-made ones, since the angle of rotation did not converge. Therefore, I made circles from thin aluminum for my diameter and my angle of rotation. Drilled holes of the required diameter (slightly larger than the purchased gobos).

The problem of the inoperative scanning module in multifunctional machines Hewlett Packard LaserJet 3380 is one of the most widespread and causes many questions and discussions among specialists in all kinds of Internet forums. Probably only the laziest specialist, or the one who has never encountered these devices, did not speak on this issue. In all this discussion, the prevailing opinion is that the problem cannot be solved in any other way, except by replacing the entire scanning module. But, it is possible that the key to solving the problem of the not working scanner in the LJ3380, you will find in this publication.

There are several problems specific to the HP LJ3380 MFP and manifested in the form of errors in the scanning module:

- errors software apparatus;

- no movement of the scanning carriage when the scanning lamp is on;

- errors in carriage movement;

- lack of glow of the scanning lamp;

- the machine is not ready, although the scanning lamp turns on and the carriage moves.

We will try to give a brief description of each problem, but we will not mention such situations when the cause of the problem is a broken connection and defects in connecting cables - they are already on the surface.

Machine software errors

This problem is really related to errors made by the manufacturer when creating the control software of the device (Firmware). The solution to this problem is offered by HP itself, and it consists in the need to replace the old erroneous version of the Firmware with a new one in which all errors have been eliminated. HP posted this software patch on its official Internet site with all the necessary instructions. made it available to any user of the device. But "flashing" the device's software helps in rare cases and cannot be considered as a serious approach to solving a serious problem. Of course, replacing Firmware sometimes gives a result, and it can be considered as the first stage in the actions of a service specialist, but you should not place serious hopes on this. How to "flash" Firmware has already been discussed many times in various sources, and this information is easy to find on the Internet "e.

No movement of the scanning carriage

When the machine is turned on, the scanning lamp lights up, but the carriage remains stationary. Therefore, the carriage cannot find the initial scanning position, which naturally leads to an error after a certain period of time. This behavior of the apparatus is caused by a malfunction of the carriage drive system, which includes a stepper motor and a motor driver microcircuit. The probability of failure of these elements is quite high, which is confirmed by practical experience. How to diagnose this problem, as well as the principles of the carriage drive system and its circuitry, we will tell you in one of the next issues of our magazine.

Errors in carriage movement

Incorrect movement of the carriage, which consists in the fact that it starts to move in the wrong direction, stops in the wrong position, etc., can be caused both by a malfunction of the motor itself and its driver circuit, and by a malfunction of the CCD (CCD).

No lamp glow

This problem lies in the completely opposite behavior of the scanner, but in the end it produces the same result. The fact that when the device is turned on, the lamp does not light, although the carriage moves, can be caused by several reasons:

- malfunction of the lamp itself;

- malfunction of the lamp inverter;

- malfunction of the voltage regulator for the inverter.

To understand this situation, we hope, the information presented below will help.

Lack of readiness of the device

If the device generates an error of warming up the scanning lamp, although the lamp is on and the carriage is moving, then this can be perceived as a loss of power by the lamp, which requires its replacement. However, nevertheless, the solution to the problem, although temporary, may be to slightly increase the voltage applied to the lamp, which leads to an increase in its brightness. You can increase the brightness of the lamp by understanding the material below.

So, in some cases, a problem with the scanner's performance can be caused by a malfunction of the circuit that forms the supply voltage of the scanning lamp. In the HP LJ3380, the scanning lamp is a cold cathode fluorescent lamp (CCFL) to which an AC high frequency and high voltage voltage must be applied. To generate this voltage, there is a special circuit that converts low-voltage DC voltage into high-voltage AC. This circuit is called inverter. As part of the inverter, a pulse transformer and a pair of transistors can be distinguished as the main elements. The inverter is designed as a separate printed circuit boardlocated on the scanning carriage and located below (Fig. 1).

Fig. 1

The inverter is connected to the CCD board using the J1 connector (Fig. 2), through which a voltage of about 10.5V - 11.5V is applied to the inverter.

Fig. 2

But the CCD board is used only as a backplane, along which only the conductive tracks pass. The DC voltage source for the inverter itself is located on the formatter board. A diagram of the board-to-board connections related to the inverter power circuit is shown in Fig. 3.

Fig. 3

This circuit will help you control the supply voltage to the scan lamp starting from the Engine Controller board.

As we found out, the power supply that generates the voltage for the inverter is located on the formatter board (see Fig. 4).

Fig. 4

This source is a DC-DC converter that converts a DC voltage of + 24V to a voltage of approximately + 11V. The appearance of a DC-DC converter is due to the fact that a voltage of this rating is not generated by the power supply unit of the device, and, in addition, there is a need to control the supply of the supply voltage to the inverter so that the lamp can be turned on and off at appropriate times.

The DC-DC converter is a buck-type switching converter, and its circuit is shown in Fig. 5.

Fig. 5

The main element of the converter is the key regulator microcircuit - LM3578AM. The functional block diagram of this microcircuit is shown in Fig. 6.

Fig. 6

The purpose of its contacts is described in Table 1.

Table 1.

№	Designation	Description
	IN -	Internal comparator input inverted.
	IN +	Internal comparator input not inverted.
		Contact for connecting a frequency-setting capacitor.
		General.
		Emitter of the internal output transistor.
		Internal output transistor collector.
		Input for current comparators. The contact can be used to control and limit the current, both of the internal switch transistor, and the entire pulse converter controlled by the microcircuit.
		Supply voltage input (from 2V to 40V).

The LM3578AM microcircuit is a key regulator with the ability to adjust the output pulse width. In the voltage regulator circuit of the scanning lamp for the HP LJ3380, this microcircuit is used to build the so-called Buck-regulator. An internal transistor of the microcircuit is used as a power switch operating in a pulsed mode, and the pulses are removed from its emitter, which corresponds to pin 5. A voltage of + 24V is applied to the collector of the transistor (pin 6), and therefore pulses with an amplitude of + 24V are formed on its emitter. Further, these pulses are smoothed by the inductor L1 and the capacitor C139, as a result of which a constant voltage of about 11V is obtained. The CR5 diode maintains the load current during periods when the internal transistor of the microcircuit is closed.

Current protection of the internal transistor (after all, it is a powerful switch of the converter) is provided by the resistor R117. The voltage drop across this resistor (between pin 8 and pin 7) corresponds to the magnitude of the collector current of the transistor and is estimated by the internal current comparator. The maximum current of the transistor should not exceed 750 mA. Current limiting is triggered if a voltage drop of more than 110mV is created across the resistor R117.

This circuit uses + 24V as the supply voltage for the microcircuit. As soon as this voltage appears on pin 8, the internal clock generator of the microcircuit should start, which can be guessed by the presence of a sawtooth voltage on pin 3. The frequency of this saw is determined by the capacitance of the capacitor C133. The smaller the capacitance of the capacitor, the higher the conversion frequency. In general, the capacitance of the capacitor should be in the range from 1 nF (approximately 100 kHz) to 100 nF (approximately 1 kHz).

In addition, when the microcircuit is started, an offset of 1V should be established at its input contacts (pin 1 and pin 2). It is formed by the internal circuits of the microcircuit, and its presence also indicates the health of the microcircuit.

The converter is triggered by the formatter microcircuit (U14) by generating a high-level signal applied to the resistor R170. Since the formatter is a microcircuit in a BGA package, it was not possible to find out exactly on which pin this control signal is generated. Even if they knew for sure, it is all the same, it is not possible to monitor this signal on the microcircuit, and therefore it is best to use the resistor R170 to diagnose the signal. At the moment when the lamp should start to glow, the formatter sets the control signal to a high level, which can be checked using a tester or an oscilloscope.

Output voltage stabilization is provided by the circuit feedbackconsisting of resistors R179 and R178.

Diagnosing the circuit

Diagnostics of the regulator of the scanning lamp is carried out by checking the signals at the test points. These control points are outlined by the diagnostician himself, based on the problem that has arisen, and also taking into account schematic diagram the regulator and the above information. Nevertheless, we, nevertheless, will once again pay attention to those signals and points of their control, which will help to form the correct conclusion.

1) It is necessary to check the presence of + 24V voltage on pin 8 of the LM3578AM regulator microcircuit (U19). Lack of voltage indicates a malfunction of either the power supply of the device or the fuse FU4. However, with such a problem, other mechanisms of the apparatus will not work either. In addition, the lack of voltage can be caused by a malfunction of the U19 microcircuit itself (its internal short circuit to ground), but this problem will be accompanied by strong heating of the microcircuit case or its physical destruction.

2) The sawtooth voltage on pin 3 and the presence of a bias voltage of 1V on pin 1 are monitored. and pin 2. microcircuits LM3578AM (U19). The absence of these voltages indicates, most likely, a malfunction of the microcircuit. However, with such a problem, it does not hurt to check the capacitor C133 for the absence of breakdown.

3) The presence of + 24V voltage on pin 6 of the LM3578AM regulator microcircuit (U19) is monitored. The lack of voltage most likely indicates a malfunction (breakage) of the resistor R117.

4) It is necessary to control the appearance of a high-level signal (about + 3.3V) on the resistor R170 (from the side of the formatter microcircuit) after a certain period of time after turning on the device. The absence of a signal indicates a malfunction of the formatter. You should also make sure that the capacitors C134 and C132, as well as the resistors R170-R173, are in good condition.

5) The presence of rectangular pulses on pin 5 of the LM3578AM microcircuit is monitored. The lack of impulses indicates:

- microcircuit malfunctions;

- malfunction of the CR5 diode ("breakdown"), while the breakdown of the CR5 diode is usually accompanied by a strong heating of the microcircuit case;

- malfunction of the capacitor C139 (leakage), which is also accompanied by the heating of the microcircuit case.

6) The presence of a constant voltage across the capacitor C139 is monitored. It should be in the range of approximately 10.7 V to 11.7 V. Complete absence of voltage corresponds to an open circuit of the inductor L1. If this voltage does not match the specified range, it is necessary to check the capacitors C139 and C142, resistors R178 and R179, as well as the load circuit of the regulator (checked by disconnecting the loop from connector J2 on the formatter board). In addition, increasing the resistance of the resistor R117 can contribute to lowering the output voltage of the regulator.

Solving the Scan Lamp Problem

As we said at the beginning of the article, one of the problems of the device is that it does not enter the ready mode, although the lamp seems to glow normally. This problem is very often associated with a malfunction of the scanning lamp itself, the luminous flux of which decreases over time. Degradation of the CCFL lamp is a natural process and it is really impossible to avoid it. Another thing is that too fast wear of this lamp occurs, possibly due to an incorrectly selected operating mode, i.e. due to errors in calculations when creating a voltage regulator or using low-quality lamps. You can put up with this by replacing the entire scanning unit or decommissioning the device, or try to change the lamp mode by increasing its brightness. Of course, an increase in the brightness of the lamp will begin to lead to an even faster degradation of the lamp, but, on the other hand, there will be an opportunity to work with the device for some time. There are several ways to increase the brightness of the lamp:

- increasing the value of the resistor R179;

- reducing the value of the resistor R178.

Changing the values \u200b\u200bof the resistors R178 and R179 changes the value of the feedback signal downward, which automatically leads to an increase in the pulse duration, i.e. to increase the output voltage.