Simple devices for logic elements

    In amateur practice increasingly adopted digital integrated circuits. HAM attracts that device, collected on them, usually do not require building or they were very simple. Large popular K155 series of chips made on the basis of transistor-transistor logic (TTL). In this series there are elements of multi-AND-NOT, flip-flops, counters, decoders, storage devices and others.
When construction of the scheme should be remembered that the output circuits can be connected to ten inputs. If you want to connect a larger number of inputs, it is necessary to use elements with higher load capacity. Free admission (unused), preferably through a resistor of 1 kOhm connected to power supply 4.5 V (up to 10 through one resistor) to the generator or logic 1.
Power supply circuits K155 series 5 ± 0,25 V.
On the concept of logical elements do not show the connection of power supply to them. Many circuits K155 series of food served to the findings of 14 (+5) and 7 (common wire).
Fig. 1 shows a schematic diagram of a sound generator, which can be used as an electronic bell. The device is made of two logical elements of 2I-NOT D1.1 and D1.2 on the principle of the multivibrator. Frequency signal, which it generates, is determined by capacitors Cl, C2 and resistors Rl, R2. Required tone sound picked Trimmer Rl, R2.
Dynamic head B1 can be any type of resistance voice coil 4 ohms. You can enable and consistent with one of the resistors, but in this case, the volume of sound will be much less.
In case chips K155LAZ are four logical element 2I-NOT. In the remaining two elements can perform another generator or build more complex device - the call with intermittent sound (Fig. 2).

Fig. 1. Schematic diagram of the electronic call

Fig. 2. Schematic diagram of the call with intermittent sound

The bell is set to break the power supply circuits (shown in Fig. 1, 2 not shown).
Call with intermittent sound consists of two multivibrators. The components of D1.1 and D1.2 assembled first, and the D1.3, D1.4 - second. As in the previous device, the frequency generated by them, is determined by the parameters RC chains - R1C1, R2C2 and R3C3, R4C4.
The first multivibrator generates pulses with a lower repetition rate, controls the operation of the second. While at the bottom of the scheme inputs elements D1.3 and D1.4 from the output element D1.2 there is no logic 0 (voltage less than 0.4 V), the second flip-flop does not work. Formed a pause. After filing multivibrator logic 0 on the elements of D1.3, D1.4 produces a signal.
Establishing device is easy: Trimmer Rl - R4 are making the necessary sound.
As in the previous case, this sound generator you want to apply the dynamic head of the resistance of the voice coil 4 ohms.
Fig. 3 shows a schematic diagram of two-tone siren. It has been three multivibrator - on the elements of D1.1, D1.2; D2.1, D2.2 and D2.3, D2.4. The first flip-flop (he works in the self-oscillating mode and generates a pulse frequency of about 1 Hz) manages the other two. Multivibrator on the elements of D2.1, D2.2 activated only when the output D1.1 logical 1 (a level not less 2,4 V), and flip-flop on D2.3, D2.4 - when logic 1 at the output of D1 .2.
The output signal from the controlled oscillator is fed to summing element D1.3, which form the two-tone.
Wish sought in establishing sound, selecting resistors R1 - R6.
Two-tone siren can also be done using a call with intermittent sound (see Fig. 2), but this would require another chip. She collected multivibrator, and one of its elements will be summing. Scheme sirens shown in Fig. 4.

Fig. 3. Schematic diagram of two-tone siren

Establishing device is reduced to the selection of resistors R1 - R6. They are making the necessary sounds.
The two chips K155LAZ easy to collect a simple probe to test the radios. Schematic diagram of the probe is shown in Fig. 5. It produces low-frequency and high-frequency modulated signals with an amplitude of about 2 V.
Low-frequency generator assembled on a chip D1. Rectangular voltage with an element DL1 through the condenser is fed to the divisor N R3R4, which reduces the output signal 10 times. With element D1.2 signal of rectangular shape supplied to one input element D2.2, managing the work of the high-frequency generator (D2.1 - D2-.4). It produces oscillations only when the upper entrance to the scheme D2.2 fed logical 1.
At high probe output signal is fed from the output element through the condenser D2.1 Sat Divider R7R8 reduces the output voltage is also 10 times.
This probe is not necessary to feed from a network source, you can use a battery 3336L. True, with a decrease in supply voltage will change the frequency and amplitude of the output signals.
Fig. 6 shows schematic diagram of another probe. High-frequency generator in it assembles the elements of the D1.1 and D1.2. Its frequency is determined by coil L1 and capacitor CL If, for example, it is necessary to probe worked in the short-wave, coil L1 should wind up on a frame 8 mm in diameter with podstroechnikom of ferrite M600NH wire PEL 0,3. It should contain 10 turns.

Fig. 4. Schematic diagram of two-tone siren call with intermittent sound

Fig. 5. Schematic diagram of a simple probe

Fig. 6. Schematic diagram of the probe with the coil inductance

Multivibrator at D2.1 and D2.2 produces low-frequency signal, which modulates the high-frequency pulse voltage. Options modulator performs an element D1.3.
In everyday life all the more widespread timers. Schematic diagram of one of them, which is easy to make yourself, is shown in Fig. 7. He made only a single chip, and consists of three components: the elements of the multivibrator D1.1, D1.2 working in self-oscillating mode, the electronic key (resistors R5 - R10, capacitors C4, C5, diode V1) and expecting multivibrator (items D1. 3, D1.4).
Multivibrator on elements of D1.1 D1.2 generates pulses of rectangular shape with a repetition rate of about 1 kHz. They are differentiated chain C1 R5 and fed to the electronic key.

Fig. 7. Schematic diagram of the timer

Job electronic key based on the opening of the diode V1 at the time of excess voltage on its anode to the cathode. With the closure of the contacts button S1 capacitor C4 is quickly discharged through the resistor R7. Voltage at the top of the scheme output resistor R6 maximum (about 250). When closing the contacts S1 capacitor starts to charge through the elements of R5 and R6. The voltage on resistor R6 decreases exponentially. Once it reaches a threshold level, which is determined by the divisor R9R10, diode V1 is opened, and the short negative pulses from the differentiating chain C3R5 through it comes to monostable multivibrator, which generates pulses of sound frequency.
When using the elements specified in the concept, the curing time can reach 20 - 30 min.
The electronic key is desirable to use a capacitor C4 MBGO on the operating voltage of at least 350 V or any other, but with a small current leakage. Diode V1 must withstand a reverse voltage greater than 250 V, and have a small reverse current. Resistor R9 - excerpts regulator should have the exponential dependence of resistance on the angle of rotation of the engine. In this case, the scale of abstracts will be linear.

Fig. 8. Schematic diagram of the power supply

In the process of establishing an electronic key Trimmer R10 set the desired maximum restraint, and then graduate scale.
Fig. 8 shows the basic scheme of the power supply, which is suitable for most devices listed in the article.
To exit the power supply can be connected indicator that signals the value of output voltage: whether it is in the range 4,75 - 5,25 V or not. Scheme of the indicator is shown in Fig. 9.
The indicator consists of two channels: on the first element of D1.1, the D1.2, D1.3 - second. The first channel is configured so that when the input voltage of more than 5.25 in the element D1.1 with resistor R1 comes standard logic 1. This output will be logical D1.1 O, V1 and the LED glows. In the second channel at the output of the element D1.3 will be logic 0 (enable LED V3) with an input voltage of less than 4.75 V. If the output elements of the D1.1 and D1.3 - logic 1 (supply voltage is within specified limits) the output D1.4 - logic 0, and the light diode V2.

Fig. 9. Schematic diagram of the voltage tester

Establish clear indicator. Connect voltage 5.25 V, Trimmer R1 achieve emission diode V1. Decrease the input voltage to 4,75 V and adjusting the resistance trimmer R2, offer the glow LED V3.
The indicators at the appropriate adjustment can be used as a probe to determine the status of logic elements.

S. Fedorova


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