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Sign-synthesizing indicators and blocks of digital indication. Radio - for beginners
Directory / Radio - for beginners We conventionally call the most important parts and assemblies of measuring and controlling instruments, electronic clocks and many other instruments and devices with visually observable digital information as digital indication blocks. They are formed by decoders - special microcircuits that convert (decode) the logical code state of the pulse counters preceding them into signals of the decimal system, and sign-synthesizing indicators - electronic devices that display information. One decoder and one character-synthesizing indicator corresponding to it form a single-digit digital indication block. What are sign-synthesizing indicators and how do they work? Of all the variety of indicators that display the logical states of the pulse counters, the most popular among radio amateur designers are gas-discharge digital indicators, each element of which is an independent number, and seven-element indicators, the numbers in which are formed by various combinations of luminous strip elements. The appearance, pinout and symbolic graphic designation of one of the gas-discharge indicators of the IN series - the indicator IN8 - are shown in fig. one.
In a glass container filled with neon (filling is indicated by a black dot), on thin metal racks, wire electrodes in the form of numbers from 0 to 9 are placed one after the other (package). These electrodes are indicator cathodes, which are indicated on the diagram by small circles with leads from them . The shape and size of the figures are made such that those of them. which are in front, perhaps overlapped those located behind them less. The function of the anode is performed by a thin grid placed in front of the package of numbers, through which the glow of all the cathodes of the numbers is clearly visible. From all the cathodes and the anode, flexible wire leads are made, the numbering of which goes in the clockwise direction (when viewed from the side of the bottom of the cylinder), as shown in Fig. 1b. Another variant of the circuit designation of the indicator is shown in fig. 1, in. The principle of operation of such an indicator is as follows. A rather large voltage (about 200 V) is applied to the anode from the positive terminal of the DC source. When connected to the negative output of the source of one of the cathodes, a glowing electric discharge occurs near this cathode, the orange-red glow of which repeats the shape of the switched on sign of the digital indicator. In the digital indication unit, the connection of cathodes-digits to the common (negative) conductor of the power source of the device is performed by a decoder. An example is a block assembled according to the scheme in Fig. 2. It is formed by the decoder DD1 and the gas discharge indicator HG1.
The K155ID1 microcircuit is a BCD decoder with a "high-voltage" output, i.e., designed to work together with a digital gas-discharge indicator. The decoder has four addressable inputs that are connected directly to the outputs of the counter operating in the 1-2-4-8 weight code, and ten outputs that are connected to the digital indicator cathodes. The decoder converts the output signals of the counter into the signals of the code of the decimal number system, which include the glow of the corresponding cathode-digits of the indicator. Mount and test the parts and the device as a whole in the following sequence. First, fix only the IN8 gas-discharge indicator on the breadboard, having previously put insulating PVC tubes on its wire leads. Nearby, mount the diode VD1, which acts in the block as a half-wave rectifier that feeds the anode circuit of the indicator, and the resistor R1, which limits the current in this circuit. The source of alternating voltage can be directly the electric lighting network, but it is better, from the point of view of electrical safety, to use for this purpose the secondary winding of the network transformer of the power supply of the lamp broadcasting receiver. Connect one of the winding leads to the anode of the VD1 diode, and solder a piece of wire in rubber or PVC insulation to the other. Strip the free end of the wire from insulation and, having connected the transformer to the mains, touch it in turn with terminals 10, 1, 2, 3, etc. until terminal 9 of the indicator. At the same time, the numbers 0, 1, 2, .... should light up in the same sequence. 9. Carry out the check with extreme caution so as not to get under high voltage. Then, on the breadboard, mount the K155ID1 decoder and connect its output terminals to the corresponding indicator input terminals. You will get a single-digit block of digital indication. Turn on the power supplies (AC and DC) and, being careful, apply low voltage to all four inputs of the decoder connected together. The number 0 should be lit in the indicator. Next, apply a low-level signal alternately to the interconnected terminals 4, 7 and 6; 4, 7 and 3; 4 and 7; 4, 6 and 3; 4 and 6; 4 and 3; four; 4, 7 and 6; 3 and 7. Leave the unnamed outputs free, which is equivalent to applying a high level voltage to them. The indicator should indicate sequentially the numbers from 6 to 1. Experimental verification of the digital display unit can be continued. For example, place another counter K155IE2 on the board and connect its outputs to the corresponding address inputs of the decoder. After that, it is necessary to apply to the input C1 of the counter from the generator a series of pulses following with a frequency of 1 ... 3 Hz. How should the indicator react to this? Cyclically indicate numbers from 9 to 9. Yes, a single-digit pulse counter counts up to 0, overflows and immediately starts counting the next ten input pulses from XNUMX. Is it possible to use other gas-discharge indicators of the IN series in such a unit? Of course you can. For example, IN8-2 or IN14. But they have a slightly different pinout. In the IN8-2 indicator, in addition to the numbers known to us, there is a separating comma sign, and in the IN14 indicator there are two such signs. However, you can recognize the pinout of these indicators without resorting to reference literature. The fact is that through the glass cylinder of the indicator it is not difficult to examine the internal racks and leads of the cathodes-digits and thus find the anode lead. If now a positive voltage is applied to the output of this indicator electrode, and the other outputs alternately touch the negative conductor of the same source of constant (or pulsating) voltage, then the luminous numbers or other signs will point you to the corresponding indicator outputs. This is also a learning experience. Seven-element indicators, which can be vacuum or semiconductor, are united by the principle of synthesizing signs of digital or alphabetic information. These signs in each category form seven luminous elements-stripes arranged in the form of a straight or slightly inclined figure eight to the right. The standard designation of the elements of such indicators and the numbers they indicate from 0 to 9 are shown in fig. 3.
As a rule, the indication of one or another sign occurs by suppressing elements that are unnecessary for this sign. So, for example, to indicate the number 0, only the element g is extinguished, for the number 4, the elements a, d and e. Seven-element indicators also allow you to indicate some uppercase (capital) letters of the Russian or Latin alphabet. To indicate the letter A, for example, it is necessary to extinguish the element d, to indicate the letter B - to extinguish the element b, etc. The appearance and variants of the conventional graphic designation of one of the vacuum luminescent indicators of the IV-indicator series IV6 (or IVZA) are shown in fig. four.
The indicator is an electronic lamp containing a cathode - a direct filament, a control grid, seven anodes - sign elements located in the same plane, and one more anode - a separating point. A constant or pulsating voltage of 7 ... ... 8 V is applied to the filament (pins 0,8 and 1,5) (depending on the type of indicator), to the grid (pin 9) and anodes-elements (pins 1-6 , 10) - constant voltage 20 ... 25 V. A hot filament emits electrons that rush to a positively charged grid, for the most part fly through it and, bombarding the anode elements, make the phosphor layer deposited on them glow. The anode-separating point (pin 11) is supplied with the same voltage as the other indicator electrodes, but not through the decoder, but from the pulse generator. In an electronic watch, for example, such a dot, flashing at a frequency of 1 Hz, separates the minutes of the current time from the hours. The indicator IV6 (or IVZA) has 12 flexible wire leads, which are counted clockwise (when viewed from below). The shortened free terminal 12 serves as the reference key. Practice shows that the signs of the IV6 and IVZA indicators shine quite brightly even at a lower voltage on the grid and anode elements. Therefore, radio amateurs often use them in designs based on the K176 series microcircuits. An example of this can be a digital indication unit, the diagram of which is shown in Fig. 5.
In it, the filament of the HG1 indicator is powered by a single G1 element with a voltage of 1,5 V, and its grid, anode elements and the DD1 microcircuit are powered by a GB1 battery with a voltage of 9 V. The anode point of the indicator is not used, therefore, the node diagram is not shown . The K176IE4 microcircuit (DD1) is a ten-day pulse counter (symbol CT2) and a converter (i.e., decoder) of its states in binary code into control signals of a seven-element indicator (symbol DC) combined in one housing. Counting pulses are fed to input C. On the right - outputs a - g, corresponding to the address inputs a - g of the indicator. The counter triggers are set to zero when a high level voltage is applied to input R, which is equivalent to breaking the circuit (using the SB1 button) between pin 5 and the common wire. The triggers are switched by the decay of positive pulses at input C. During operation of the device, signals are generated at the outputs ag of the counter-decoder, which ensure that the numbers on the indicator glow corresponding to the logical state of the counter. Output P (pin 2) of the microcircuit is a transfer output, on which a high-level pulse decay is formed at the moment the counter transitions from state 9 to state 0. Then, on the breadboard, mount the K176IE4 chip, connect its outputs to the corresponding indicator terminals, input S (pin 6) with a common wire and apply pulses from the generator to input C (pin 4) with a frequency of 1 ... 2 Hz. Now the indicator will sequentially cycle through the numbers from 0 to 9. To transfer the indicator readings to zero, it is necessary to apply a high-level voltage to the input R (pin 5) of the microcircuit or break the circuit between pin 5 and the common wire. Semiconductor seven-element alphanumeric indicator is formed by 7 light-emitting diodes having the form of strips, which, as in vacuum fluorescent indicators, are located in the same plane as a "figure eight" (Fig. 6).
By passing a direct current through one or a group of corresponding LED elements, a luminous image of a number or letter is obtained. According to the method of connecting the electrodes of the LEDs and the polarity of turning on the power, indicators of two groups are distinguished: with a common cathode and with a common anode. For the indicators of the first group, the cathodes of all LEDs are interconnected (Fig. 6, a), and for the indicators of the second group, the anodes of all LEDs (Fig. 6, b). To control indicators with a common cathode, a voltage of positive polarity is applied to the input (anode) terminals, and to control indicators with a common anode - negative polarity with respect to the common wire. The designs of semiconductor seven-element indicators are very diverse. For an example in fig. 7, a and b show the appearance and symbolic graphic designation of the AL304 series indicator. Indicators of this series with letter indices A, B and C-with a common cathode, and with letter indices G and G-with a common anode.
The dimensions of the case of such an indicator are 5,3x6,3 mm, the dimensions of the sign are 2x3 mm, the length of the leads is about 6 mm. Through the transparent body, it is easy to see the entire "stuffing" of the indicator and recognize its pinout. Some other single-digit semiconductor seven-element indicators, for example, the ALS312, ALS320 series, have a similar design. And in fig. 7, c shows a diagram of a digital indication unit, in which the AL304B indicator with a common cathode is used. The K514ID1 (DD1) microcircuit is a decoder designed to work together with a seven-element indicator with disconnected LED anodes. When signals are received at its inputs from the pulse counter operating in the code 1-2-4-8, the indicator displays the logical state of the counter. Such a digital indication unit can work in a design based on K 155 series microcircuits. If an indicator with a common anode, for example, AL304G, is used in it, then the decoder should be K514ID2, designed to work with just such an indicator. However, if the decoder of this series is replaced by the K176IE4 microcircuit, then such a digital indication unit can be used to work in devices without an additional decoder. Now, briefly about multi-digit indicators, the most widely used in microcalculators, electronic watches and many other devices and devices of digital technology of increased complexity. These include, for example, indicators of the ALS311, ALS339, ALS348 series. Each of them consists of five LED indicators, similar to the indicators of the ALS304 series already familiar to you (Fig. 7, a), located in a "line" case. The anode elements do not have any electrical connections with each other, therefore any discharge included in such a sign-synthesizing device can work as an independent single-digit seven-element indicator. Another example of a multi-digit character-synthesizing device is the IVL 1-7/5 vacuum luminescent indicator, the appearance of which is shown in fig. 8, a.
In its glass case with dimensions of 130X45 mm, with sixteen flexible plate leads, four seven-element luminescent indicators, four digits and two dividing points, forming one more digit, are located "in a row". In the designation, the number 7 indicates the number of elements in a full digit, and the number 5 indicates the number of digits. The cathode is three filaments connected in parallel (pins 1 and 16). According to the principle of operation, the device is similar to the indicator of the IV series (see Fig. 4), but the elements of the indicators of the 1st, 2nd, 4th and 5th digits of the same name are interconnected into groups, and each group has a separate output. Grids of all digits and separating points K and L of the 3rd digit of the indicator also have separate conclusions. IVL indicators 1-7/5 are most widely used in industrial and amateur electronic watches. But to control the sign-synthesizing elements of such or similar multi-digit indicators, a so-called dynamic display system is required. In the schematic diagrams, the indicator IVL 1-7/5 is depicted in the form of a table shown in fig. 8,b Considering it, it is not difficult to figure out which of the indicator's conclusions is related to one or another of its elements. The extreme conclusions 1 and 16 are the conclusions of the common direct-heated cathode, 2 and 10 are the conclusions of the separating points K and L of the third category, and 3, 6, 9, 11 and 14 are independent conclusions of the grids of five digits of the indicator. Pin 4 is the common output of interconnected d elements, pin 5 is the output of f elements, the output of 7-elements, etc.
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Comments on the article: Alexey Is it possible to connect the IN-2 lamp to the K176ID1 chip instead of the K155ID1? Petrovich Pinout indicator IVL1-7/5 in fig. 8 is not true. Oleg If only IVL 2-7/5 were painted like that!..
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