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Microcircuits of the K176 series. Radio - for beginners

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This series includes more than three dozen digital microcircuits of various degrees of integration, allowing you to create a variety of instruments and devices of digital technology. All of them are similar in design and principle of operation to the K155 series microcircuits. So, for example, the K176LA7 chip, like the K155LAZ chip, contains four 2I-NOT logic elements in its case. The K176TM2 chip, like the K155TM2 chip, is two D-flip-flops that can become countable if their inverse output is connected to the D input. In short, all those experiments and experiments and the devices and devices you previously designed can be repeated on the corresponding K176 series microcircuits.

But, and this "but" must always be remembered, the K176 and K155 series microcircuits similar in functionality are not interchangeable! It is impossible, for example, to simply replace the K155TV1 microcircuit with the K176TV1 microcircuit, although both of them are JK flip-flops, it is impossible to replace only one of the K155LAZ microcircuits with the K176LA7. The fact is that the K176 series microcircuits are designed for a nominal supply voltage of 9V ± 5%, although they remain operational at a voltage within 4,5 ... 12 V. And the voltage of their logical levels is not the same. At a voltage of 9 V, the low-level voltage corresponding to logic 0 is not more than 0,3 V (for K155 series microcircuits, not more than 0,4 V), and the high level is not less than 8,2 V (for K155 series microcircuits, not less than 2,4 V). All this and some other things do not allow you to directly connect the K176 series microcircuits to the K155 series microcircuits and, therefore, use them to work together in one design.

The main feature and advantage of the K176 series microcircuits is efficiency. Compared to the K155 series microcircuits, they consume many times less energy from the power source. For example, the K176IE2 pulse counter consumes a current of about 100 μA from the power source, and the current consumed by the K155IE2 counter reaches 50 mA. This is explained by the fact that the basis of the K176 series microcircuits are field-effect transistors of the MOS (metal-oxide-semiconductor) structure, and not bipolar transistors, as in TTL microcircuits. In this regard, the level of signals applied to the control inputs of the microcircuits also changes. So, for example, to set the K155TV2 D-flip-flop to a zero or a single state, you applied a low-level signal to its R or S input. A similar trigger of the K176TV2 microcircuit is set to the same states by applying a high-level signal to the R or S input.

We should not forget one more feature of the K176 series microcircuits: they are detrimental to electrostatic charges! Here are some tips to prevent these troubles. If the microcircuit is stored in a metal box or its leads are wrapped in foil, then before taking the microcircuit by hand, you should first touch the box or foil.

To exclude accidental breakdown of field-effect transistors of the microcircuit by static electricity during installation, the static potentials of the electric soldering iron, the soldered part and the body of the installer himself must be equalized and minimized. To do this, a plate of tin is strengthened on the handle of the soldering iron with several turns of bare wire and connected to the metal parts of the soldering iron through a resistor with a resistance of 100 ... 200 kOhm. When mounting, the fingers of the free hand touch the power conductor on the circuit board of the device.

The power of the electric soldering iron used for mounting structures on K176 series microcircuits should be 25 ... 40 W. It is advisable to connect the soldering iron to the network through an isolating transformer, and connect the plate on the handle with a flexible conductor to ground through a 1 MΩ resistor. The soldering time of each pin should not exceed 3 s, and the soldering of the adjacent pin should be started after 10 s.

It is recommended to start soldering the K176 series microcircuits from the power leads, after temporarily connecting a resistor with a resistance of 1 ... 2 kOhm between the power wires on the board. If a zener diode is already soldered into the power circuit, then there is no need for such a resistor.

And one more warning: the supply voltage of the device on the K176 series microcircuits must be turned on before control signals are applied to its input.

We advise you to start your acquaintance with the K176 series microcircuits with an experimental check of the operation of logic elements in generators. First of all, we believe that it is necessary to master the K176LA7 chip, as the most widely used in amateur radio designs.

The conventional graphic designation of the K176LA7 microcircuit is shown in fig. 1a.

Rice. 1 Microcircuits of the K176 series

It differs from the K155LAZ microcircuit only in the numbering of the outputs of two medium (according to the scheme) logical elements 2I-NOT. The positive wire of the power source is connected to pin 14, and the negative wire to pin 7. The power source can be two 3336 batteries connected in series, or a power supply with a stabilized output voltage of 9 V.

The same figure shows the circuits of two variants of a single vibrator that generates single pulses. The first of them (Fig. 1b) is triggered by a recession, and the second (Fig. 1c) by the front of a high-level pulse. In both versions of such a single vibrator, the duration of the generated pulse is determined by the capacitance of the capacitor C2.

The operation of the first version of the device is as follows. In the initial (standby) state, the capacitor C2 is discharged, therefore, a high level voltage is maintained at both inputs of the DD1.1 element (pins 1 and 2) and the output of the DD1.2 element. A short low-level signal, created by the decay of the input pulse, differentiates the C1R1 circuit, as a result of which the element DD1.1 switches to a single state, and DD1.2 to zero. In this case, the low-level signal that appears at the output of the second element is transmitted through the capacitor C2 to the input of the first element and maintains it in a single state. At the same time, the capacitor begins to charge from the supply voltage through the resistor P2. As soon as the voltage on the left (according to the scheme) plate of the capacitor reaches the threshold value, the element DD1.1 will immediately switch to the zero state. At this moment, a positive voltage drop will appear at the output of the DD1.2 element, which will be transmitted through the same capacitor C2 to the input of the first element and switch both elements of the one-shot to its original state. Diode VD1, shown in the diagram by dashed lines, is turned on in cases where it is required to switch the single vibrator to standby mode as quickly as possible.

Briefly about the single vibrator of the second variant (Fig. 1, c). Its right (according to the diagram) part, which includes elements DD1.3, DD1.4, capacitor C2 and resistor R2, works in exactly the same way as a single vibrator on the elements of the K155LAZ microcircuit. The duration of the low-level pulse generated at its output is about 3,5 s.

In order for the duration of the generated pulse to be stable, the pulse that triggers the single vibrator must also be fairly stable. Therefore, it is advisable to run such a device through a short pulse shaper, made in our example on elements DD1.1 and DD1.2. In the initial state, a low-level voltage acts at the input of the device, which is also applied to the lower input of the DD1.2 element, Capacitor C1 is discharged at this time. A high-level input pulse charges this capacitor.

But the state of the element DD1.2 does not change, since a low level voltage is stored at its upper input. And only after the termination of the input signal and the appearance of a high-level voltage at the upper input of the DD1.2 element, a very stable short low-level pulse is formed at the output of this element, which starts the single vibrator assembled on the logic elements DD1.3 and DD1.4.

The next example of the practical application of the K176LA7 microcircuit is pulsed voltage generators. In fig. 2 you see diagrams of three variants of the generator.

Rice. 2 Generators

They should remind you of similar generators on the elements of the K155LAZ chip. The pulse repetition rate of the first two generators (Fig. 2, a and b) is 1 ... 1,5 kHz.

The third option (Fig. 2c) is similar to a discontinuous signal generator. It is formed by two interconnected generators, one of which generates bursts of pulses at the output with a repetition rate of about 1 Hz, and the second generates filling pulses with a frequency of about 1 kHz. The duration of the bursts of pulses is 0,5 s. The generator is turned on by applying a high-level control voltage to the lower input of the DD1.1 element. The first generated pulse at the output of the generator occurs immediately after this enable signal.

One of the designs suggested to you earlier for repetition was a slot machine Red or green. The logical elements 2I-NOT and the JK-trigger of TTL microcircuits worked in it. The function of indicators was performed by incandescent lamps included in the collector circuits of transistor switches. Is it possible to repeat such a slot machine using K176 series chips for it? Yes, you certainly may. It is only necessary to replace the K155LAZ chip with K176LA7 (taking into account the difference in the pinout), and K155TV1 with K176TV1. Resistor R1 will need to be replaced with another one with a resistance of 300 ... 500 kOhm, and the capacitance of capacitor C1 should be 0,1 uF. The effect of the game will be the same as with that machine.

But you can also make a similar slot machine according to the scheme shown in Fig. 3.

Rice. 3 Slot machine "Red or green" on K176LA7 chips

It uses all four elements of the K176LA7 chip. Two of them (DD1.1 and DD1.2) operate in a pulse generator, the repetition rate of which is determined by the values ​​​​of the resistor R1 and capacitor C1, and the other two (DD1.3 and DD1.4) perform the function of matching stages. To the outputs of these elements through transistors VT1 and VT2, LEDs HL1 of red glow and HL2 of green are connected. When you press the SB1 button, the generator starts to work and the elements DD1.3 and DD1.4 alternately, with the frequency of the generator, switch from one logical state to another. The LEDs flash at the same frequency. But as soon as the button is released, its contacts are again closed by the time-setting capacitor C1 and the generator will stop working. In this case, a high level voltage will appear at the output of one of the matching elements, and a low level voltage will appear at the output of the other. The one of the LEDs that is connected to the element with a high output voltage will turn on.

Such a slot machine can also be considered as a random number generator: it is impossible to predict in advance which of its outputs will have a logical 1 or a logical 0.

You probably noticed that in the generators that we talked about here, the resistance of the timing resistors is much higher than in similar generators based on the K155 series microcircuits. Resistors are chosen such (but not less than 50 kOhm) so that the current flowing through them is as small as possible and does not load the microcircuits operating in the input signal source. The maximum resistance of such resistors is limited mainly by the possible current leakage in circuit boards, the leakage resistance of which reaches tens of megaohms. The capacitance of the capacitors of the time-setting circuit of the generators should not be less than 100 pF in order to significantly exceed the capacitance of the installation of the device.

The K176 series has a K176LP1 chip, which is called a universal logic element. Its versatility lies in the fact that it can be used both as three independent NOT elements, and as a ZILI-NE element, and as a ZI-NE element, and as a NOT element with a large branching factor (it allows you to connect a large number of other microcircuits to the output).

The diagram of the electronic "stuffing" of this microcircuit is shown in fig. 4a.

Rice. 4 Chip K176LP1

It is formed by six field-effect transistors, three of which (VT1-VT3) with an n-channel, the other three (VT4-VT6) with a p-channel. The total number of pins is 14. The supply voltage is applied to pins 14 (+9 V) and 7 (common). Conclusions 6, 3 and 10 are input, the rest are output. Logic elements of different functional purpose are obtained by appropriate connections of input and output terminals. So, if you connect conclusions 13 and 8, 1 and 5 to each other, you will get three inverters (Fig. 4, b). In order for the IC to become an inverter with a high output (with a large branching factor), all input pins and all output pins must be connected together, as shown in Fig. 4, c. Other pin connection combinations make it possible to turn the microcircuit into a 3OR-NOT element (Fig. 4, d), a ZI-NOT element (Fig. 4, e), a 176OR-AND-NOT element missing in the K2 series (Fig. 4, f) and multiplexer with two inputs (Fig. 4g).

The multiplexer according to the scheme of Fig. 56, three inputs - A, C and B and one output - D. At a high level voltage at input C, it passes a signal to output D from input A, and at a high level voltage, from input B. Moreover, at the same levels voltage at input C, the signal from output D can pass to input A or B.

We strongly recommend that you experimentally check the operation of the K176LP1 chip, and especially as a multiplexer, the transmitted signal of which can be both digital and analog.

With some other microcircuits of the K176 series, such as flip-flops, pulse counters, decoders, you will get to know more closely in the course of designing a digital frequency meter, electronic clocks and other devices of increased complexity, which are still to be discussed. Now we intend to talk a little about the K176IE5 microcircuit, one of the group of microcircuits of this series, specially designed for use in electronic time meters.

The conventional graphic designation of this microcircuit and a typical circuit for switching it on are shown in fig. 5, a and b.

Rice. 5 Chip K176IE5

The microcircuit consists of a pulse generator designed to work with an external quartz resonator at a frequency of 32 Hz, and two frequency dividers - nine-bit and six-bit, which together form a fifteen-bit binary frequency divider of the generator. The quartz resonator ZQ768, together with the time-setting elements of the generator, is connected to terminals 1 (input Z) and 9 (output Z). The generator signal with a frequency of 10 Hz, which can be controlled at the outputs K and K, is fed to the input of a nine-bit frequency divider. At output 32 (pin 768) of this divider, pulses with a repetition rate of 9 Hz are generated. This generator signal can be applied to input 1 (pin 64) of the second divider - six-bit. To do this, you just need to connect pins 10 and 2. Then, from output 1 (pin 2) of the fifth digit of this divider, it will be possible to remove a signal with a frequency of 14 Hz, and from output 4 (pin 2) of the sixth digit, with a frequency of 15 Hz, This stable signal with a frequency of 5 Hz in electronic watches is usually used as the initial second impulses. And if "that signal is applied to the input of an additional frequency divider with a division factor of 1, pulses with a repetition rate of 1/60 Hz will be generated at its output, that is, minute pulses of the time counter.

The R input (pin 3) of the microcircuit serves to set the initial phase of the oscillations generated at its outputs. When a high level voltage is applied to it, a low level voltage occurs at outputs 9, 10 and 15. After removing the setting level, the corresponding signals appear at these outputs, and the decay of the first high-level pulse at output 15 (1 Hz) occurs after 1 s. Capacitors C1 and C2 serve to fine-tune the frequency of the crystal oscillator. With a decrease in their capacity, the generation frequency increases, and vice versa. The frequency of the generator is set: roughly by selecting capacitor C1, exactly by trimming capacitor C2. The resistance of the resistor R2 can be in the range of 1,5 ... 20 MΩ.

Chip K176IE5 can work in a stopwatch, and similar to it, but more complex K176IE12 - in an electronic clock. Nevertheless, now, as they say, without postponing for tomorrow, you can test it in operation, as a source of exemplary frequency signals. The 64 Hz signal can be heard on high-impedance headphones. Signals with a frequency of 1 and 2 Hz can be observed visually by connecting transistor indicators with LEDs or incandescent lamps in collector circuits to pins 5 and 4 of the microcircuit.

However, the K176IE5 chip can be tested without a quartz resonator. In this case, the timing generator circuit, made up of capacitor C1 and variable resistor R2, is connected to the microcircuit, as shown in Fig. 57, in. Such a generator is set up by selecting a capacitor C2 and a variable resistor R2, achieving the appearance of a signal with a frequency of 15 Hz at the output 1. An hour or two spent in experiments with this microcircuit will not be in vain.

For experimental verification and power supply of structures on K176 series microcircuits, you can mount an independent network unit with a fixed output voltage of 9 V. For example, according to the circuit shown in fig. 6.

Rice. 6 AC adapter

In it, the output circuit protection system is formed by a germanium npn transistor VT1, a silicon diode VD2 and a resistor R1. Diode VD2 in this case performs the function of a stabistor-stabilizer of the forward voltage acting on it, equal to 0,6 ... 0,7 V. While there is no short circuit in the output circuit, the protection system transistor is closed, since at this time the voltage on its base is emitter is negative and has no effect on the operation of the block.

In the event of a short circuit, the emitter of the transistor VT1 is connected to a common wire through a small circuit resistance. Now the voltage at the base of this transistor with respect to the emitter becomes positive, which is why it opens and shunts the zener diode VD3. As a result, the regulating transistor VT2 of the voltage regulator almost closes and the current flowing through it is limited to a safe level.

As a network transformer T1, you can use a TV vertical scan transformer (for example, TVK-70L2, TVK-110L2 or TVK-110A). Any other transformer that lowers the mains voltage to 10 ... 12 V is also suitable. The KTs402E (VD1) rectifier unit can be replaced with four diodes of the KD105 or D226 series, turning them on in a bridge circuit. Transistor VT1 can be any of the series MP35 - MP38, with a coefficient h21E of at least 50.

The design of the power supply is arbitrary.

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