|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
BOOKS AND ARTICLES
Devices on logical elements. Radio - for beginners
Directory / Radio - for beginners Let's start with a self-oscillating multivibrator. Being a universal device, it can find a variety of applications. Take, for example, a multivibrator with three logic elements. When mounted with a transistor indicator, it becomes a light pulse generator that can be used for a lighthouse model. If the transistor is of medium or high power, for example, KT801A, several miniature incandescent lamps connected in parallel can be included in its collector circuit - they will decorate a small Christmas tree. If the capacitance of the multivibrator capacitor is 1 μF, and the constant resistor R1 is variable, with a resistance of 1,5 or 2,2 kOhm, then an audio frequency oscillation generator will be obtained, suitable for testing the performance of broadcasting receivers, audio frequency amplifiers. A DEM-4m telephone capsule or a transistor indicator can be connected to the output of such a device, but with a dynamic head in the collector circuit. You will get a sound generator that can be used as a house call or used to study the reception of the telegraph alphabet by ear. In the first version, the generator supply voltage can be supplied through the bell button, in the second - through the contacts of the telegraph key. The frequency of the generated pulses within 800 ... 1000 Hz is set by a variable resistor or a selection of a constant resistor replacing it. The next example of using a multivibrator is an intermittent audio signal generator (Fig. 1).
The device consists of two interconnected multivibrators, made on the logic elements of one K155LAZ chip. The multivibrator on the elements DD1.3 and DD1.4 generates oscillations with a frequency of about 1000 Hz, which the DEM-4m capsule (BF1) converts into sound. But the sound is intermittent, because the operation of this multivibrator is controlled by another, assembled on logical elements DD1.1 and DD1.2. It generates clock pulses with a repetition rate of about 1 Hz. The tone signal in the phone sounds only during those periods of time when a high voltage level appears at the output of the clock multivibrator. The duration of sound signals can be changed by selecting capacitor C1 and resistor R1, and the pitch of the sound can be changed by selecting capacitor C2 and resistor R2. A single vibrator, supplemented by a light signaling device (Fig. 2), can become the basis of a slot machine or attraction. For example, an attraction under the conditional name "Extinguish the candle." The attraction itself is a model of a burning candle on a stand. If you strongly blow on the candle, then the HL1 incandescent lamp disguised in its "wick" should go out, and after a while turn on again.
The "secret" of the attraction is that the wall of the stand behind the candle is a light opaque fabric, on the reverse side of which, opposite the "wick" of the candle, a small tin plate is fixed. This is the contact of the sensor-switch SF1. At a distance of 3 ... 5 mm from it, the end of a piece of thick wire is fixed - the second contact of the switch. When they blow on the "candle", the air jet bends the fabric wall of the box and the switch contacts close. A low-level pulse appears at the output of the one-shot, which closes the transistor and extinguishes the lamp. Another example of the possible use of such an automaton is a shooting range for "shooting" a tennis ball. The "apple" of the target is a metal plate with a diameter of 80 ... 100 mm - this is one of the SF1 contacts. At a short distance from the first, the second contact is strengthened. With an exact hit in the bull's-eye, the contacts close for a short time and the signal lamp goes out. But you can make it so that the indicator lamp, on the contrary, lights up when the target is accurately hit. In this case, it is only necessary to use a p-n-p transistor for the indicator, for example, from the P213 or KT814 series, and swap the connection of its emitter and collector leads, as shown in Fig. 2b. In this case, the resistor in the base circuit of the transistor can not be included. A single vibrator is also of interest as a single pulse generator for testing the operability of instruments and devices of digital technology, which we will talk about a little later. Now let's give a few more examples of the practical application of a self-oscillating multivibrator in amateur radio designs. On fig. 3 shows a diagram of the simplest measuring device - a probe, with which you can check the quality of the electrical contacts of the installation, the switch, the integrity of the coil of the oscillatory circuit, the health of the diode, the quality of the capacitor, the pn junction of the transistor.
The basis of the probe is a symmetrical multivibrator based on elements DD1.1 and DDl.2, which generates pulses with a repetition rate of about 1 kHz. The probe indicator is the HL1 LED or high-impedance headphones TON-1, TON-2 or TEG-1 connected to a two-socket socket XS1. Probes XA1 and XA2 act as contacts of a kind of switch, through which the voltage of the power source GB1 is applied to the microcircuit. While the probes are not closed to each other, the power circuit is broken and the multivibrator does not work. If the probes touch the ends of the conductor or the terminals of a working inductor, the power circuit of the microcircuit will be closed and the multivibrator will begin to generate electrical oscillations of sound frequency. At a high voltage level at the output (at pin 6) of the multivibrator, the HL1 LED will light up, and at a low level it will go out. And since the frequency of the generated pulses is quite high, the eye does not notice the blinking of the LED - it seems to shine continuously. If, however, there is a break in the tested conductor or in the coil, then neither the LED will glow, nor the sound in the phones will be. To test a semiconductor diode, probe probes are connected to its terminals - first in one polarity, and then, swapped, in the other. With one connection, when the diode is turned on in the forward direction relative to the power source, there should be light and sound signals, but not in the reverse direction. The appearance of signals at any polarity of the probe connection will indicate a thermal breakdown of the p-n junction of the diode, and the absence of signals at any polarity of the connection will indicate an open circuit in the internal circuit of the diode. Similarly, the health of the collector and emitter p-n junctions of transistors is checked. The serviceability of capacitors is checked for breakdown (short circuit of the plates) by the absence of a light (or sound) signal when their leads are touched with probe probes. When checking a high-capacity capacitor, at the moment the probe probes are connected to its terminals, a short sound signal and a flash of the LED may appear. These signals are caused by the charging current of the capacitor. They are the longer, the larger the capacitance of the tested capacitor. The power source of such a probe can be a 3336 battery or three galvanic cells 316, 332 connected in series. On logical elements 2I-NOT, you can build a simple generator of sound frequency (3H) and radio frequency (RF) oscillations to test the paths of broadcasting receivers. An example is the device, the circuit of which is shown in Fig. four
The generator of sound frequency oscillations (about 1 kHz) is a multivibrator on the elements D.D1.3 and DD1.4. The oscillations generated by it through the inverter DD2.2, capacitor C5 and socket XS2 "ZCH" with the help of the XA1 probe inserted into this socket are fed to the input of the audio frequency amplifier under test. The radio frequency oscillation generator is formed by logic elements DD1.1, DD1.2, coil L1 and capacitors C1, C2. The frequency of its oscillations, determined mainly by the inductance of the coil L1, can be changed within small limits by a variable capacitor C1. Element DD2.1 performs the function of a mixer device. Its input terminal 1 receives radio frequency oscillations, and its output 2 - audio frequency. As a result, a radio frequency pulse signal modulated by audio frequency oscillations is formed at the output of the element. Through the capacitor C4 and socket XS1 "RF", it is fed to the input of the radio frequency path (or one of its nodes) of the receiver under test. The coil L1 of the radio frequency generator circuit can be wound on a frame with a diameter of 8 ... 9 mm with a piece of ferrite rod 600NM inside. In order for the probe to work in the range of 3 ... 7 MHz, 50 must be wound on the frame. . .55 turns of PEV-2 wire 0,2.. .0,3. As a variable capacitor (C1), you can use the tuning PDA-1. The design of such a probe generator is arbitrary. To power it, it is desirable to use a 5V voltage source, but a 3336 battery is also possible. And one more example of the practical use of logical elements of digital microcircuits is the game "Crossing". The content of this game is based on an old logical problem about a wolf, a goat and a cabbage, which the carrier must transport without loss to the opposite bank of the river. But the boat is so small that in addition to the carrier itself, it can only accommodate one passenger or cargo. It is impossible to leave a wolf with a goat or a goat with cabbage on the shore - there will certainly be losses. You can only leave a wolf with cabbage together without supervision. What should the carrier do in such a situation? To solve this problem, the radio amateur I. Sinelnikov from Kaliningrad proposed a gaming electronic device based on logical elements 2I-NOT and ZI-NOT, the schematic diagram of which you see in fig. 5.
With switches SA1-SA4, the player performs the "transportation" of passengers and cargo to the opposite bank of the river. So, for example, if he believes that the first goat should be transported across the river, he moves down (according to the scheme) the movable contact of the switches SA2 "Goat" and SA1 "Carrier". The position of the switch handles on the front panel of the box in which the game is mounted reflects the current situation at the crossing. Elements DD1.1, DD1.2 and DD2.1, DD2.2 form a logical node that generates an erroneous move signal, in which a dangerous situation arises on one of the banks of the river (a wolf can eat a goat, and a goat can eat cabbage). An error is signaled by the LEDs HL1 and HL2, each of which is located on its "own" bank, and the sound signal generated by the Dynamic Head BA1. How does this slot machine work? In the initial state, when all passengers, cargo and carrier are on the same bank of the river, which corresponds to the position of the SAI-SA4 switches shown in the diagram. For a story about the operation of the logical node, we will assume that the machine is powered, that is, the contacts of the SB1 button are closed. A high voltage level acts at the output of the elements DD1.1, DD1.2 and DD2.1 of the logical node and, therefore, the LEDs do not shine (due to the fact that the anode and cathode of each of them have almost the same voltage, the current through the LED does not leaks), and the output of the element DD2.2 is a low level. When the power is turned on with the SB1 "Crossing" button, a low voltage level occurs at the input pin 2 of the DD1.1 element and the input pin 3 of the DD1.2 element, as well as at both inputs of the DD2.1 element. For elements 2I-NOT and ZI-NOT, this is enough for a high voltage level to appear at their output. Both inputs of the DD2.2 element at this time remain free, therefore, there is a high voltage level on them, and at the output of the element (pin 8), and hence at the lower input of the DD1.2 element according to the circuit, with which it is connected, - low voltage level. Suppose that the player in the first move transports a goat to the other side. To do this, he must move the knobs of the switches SA2, SAI to another position and press the button SB1. In this case, all four elements of the logical node will remain in their original state and none of the LEDs will turn on. And if you try to be the first to transport the wolf? In this case, the SA3 switch will create a low voltage level at the upper input of the DD2.2 element according to the circuit and a high level will appear at the lower input of the DD1.2 element. The signal of the same level will be on the other two inputs of the element DD1.2, as they will be free. As a result, a low voltage level will appear at the output of the DD1.2 element and the HL2 LED will turn on - a signal of a dangerous situation (a goat remaining on the shore can eat cabbage!). And the HL1 LED, located on the other side of the river, will remain off, since at this time the SAI switch will create a low voltage level at the top input of the DD1.1 element. From the outputs of the elements DD1.1 and DD1.2, a signal of a dangerous situation (low level) is also supplied to the input terminals 9 and 10 of the element DD1.3. When a low level appears on at least one of them, the element switches to a single state, which leads to the launch of a multivibrator assembled on elements DD2.3 and DD2.4. The oscillations generated by it with a frequency of about 500 Hz amplify the step on the VT1 transistor, which is turned on by an emitter follower, and the BA1 head emits an alarm sound signal. The SA5 switch can be used to turn off the audible signaling, which notifies of an error during the solution of the problem, leaving only the light signaling. Resistor R5 limits the base current of transistor VT1. Through the resistor R3, a high voltage level is applied to the upper input of the DD1.3 element, which protects the signaling unit from various electrical interferences. Trimmer resistor R6 sets the desired sound volume of the BA1 head. The details of the gaming machine, except for the switching elements, LEDs and dynamic head, can be mounted on a printed circuit board with dimensions of 70x25 mm (Fig. 6, a) and placed in a plastic or plywood box with dimensions of approximately 120x90x50 mm (Fig. 6, b).
On the front panel of the box there is a drawing of a river, along the channel of which switches SAI-SA4 are fixed, and on opposite banks - LEDs HL1 and HL2. Here are the SA5 switch and the SB1 "Crossing" button. Switches SAI-SA5-toggle switches MT-1 or TV2-1, button SB1-KM1-1. Dynamic head VA1-power 0,1 ... 0,25 W, for example 0,25GD-10. The power source can be a 5V full-wave rectifier or a 3336 battery. Before starting to solve the problem, all switches must be in their initial position, corresponding to the situation when all passengers, cargo and carrier are on the same bank of the river. Then they start crossing to the other side - they put the handles of the corresponding switches so that they are directed towards the coast where the boat should sail, and by pressing the "Crossing" button, they check the correctness of the move. If at the same time a light or sound signal of an error appears, the move is considered incorrect - you need to look for another solution to the problem. To make sure that the slot machine works correctly, you need to know the course of solving a logical problem. He can be like that. First, the carrier transports the goat to the other side. Then he comes back and takes the cabbage. On the other side, he leaves the cabbage and takes the goat. Having transported the goat back, he puts the wolf in the boat and transports him to the cabbage, after which he returns and takes the goat. Thus, the problem is solved in seven moves. Can there be other solutions to the problem? Think.
Traffic noise delays the growth of chicks
06.05.2024 Wireless speaker Samsung Music Frame HW-LS60D
06.05.2024 A New Way to Control and Manipulate Optical Signals
05.05.2024
▪ ST25R3916 13,56MHz Universal NFC/RFID Reader ▪ Eternal batteries based on nanodiamonds and radioactive waste ▪ The robot will find and neutralize a traitor colleague ▪ Developed a material that compresses when stretched
▪ section of the site Security and safety. Article selection ▪ Article One thousand and one nights. Popular expression ▪ article Which animals have the most genes? Detailed answer ▪ Supervisor article. Job description
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page