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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Encyclopedia of radio electronics and electrical engineering / Automobile. Security devices and alarms

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This device provides continuous monitoring of the state of the protected object over the radio. In case of any unauthorized impact on it or failure of the transmitter, the receiver will immediately notify the owner of this with an alarm signal.

This device provides continuous monitoring of the state of the protected object over the radio. In case of any unauthorized impact on it or failure of the transmitter, the receiver will immediately notify the owner of this with an alarm signal.

The radio channel of the described guard device consists of a transmitter installed in the car and a receiver located at the owner. In standby mode, the transmitter emits a frequency-modulated message every 16 s at a frequency of 26945 kHz (you can learn about the choice of radio channel parameters from publication [1]). The duration of the message is 1 s. modulation frequency - 1024 Hz. When security sensors are triggered, the transmitter switches to continuous modulated emission mode, to which the receiver will respond with an alarm signal. The same signal will sound if the receiver does not receive another message 16 seconds after the beginning of the previous one.

Such an algorithm of the radio watchman's operation ensures high reliability of protection, since any defect - damage to the antenna, discharge of the battery or failure of the transmitter - will immediately be marked with a warning signal.

The output power of the transmitter is 2 W, the sensitivity of the receiver is better than 1 μV. With a small transmitter antenna mounted behind the windshield of a car and a receiver whip antenna about 50 cm long, the range of the radio channel exceeds 500 m. If, however, full-size antennas are used on the car and at the receiving place, the range can reach several kilometers.

The watchman transmitter circuit is shown in fig. 1. On the DD1 and DD2 microcircuits, a node is assembled that provides the necessary time rhythm for its operation. The master oscillator of the DDI chip is stabilized by a "clock" quartz resonator ZQ2. The signal from the output F of the counter of the DD1 chip [2] modulates the transmitter generator, and from the output S1 it goes to the input CN of the counter DD2.1 and the diode-capacitor switch VD2R17C20R18.

car radio watchman
(click to enlarge)

While the output of the counter DD2.1 is low logic level, pulses with a frequency of 1 Hz pass through the switch and reset the counter DD2.2 (Fig. 2. Diagrams 2 and 3). When a high logic level appears at the output 8 of the counter DD2.1, the diode VD2 closes and the pulses at the input R of the counter DD2.2 stop coming. At the moment of the appearance of a negative drop at the input of the CP counter DD2.2, it goes into a single state and a high logic level appears at its output 1.

car radio watchman

The next pulse from the output S1 counter DD1. passing through the opened diode VD1. resets counter DD2.2. Thus, the counter DD2.2 generates at output 1 high-level pulses with a duration of 1 s with a repetition period of 16 s (Fig. 4).

High-level pulses from the output of the counter DD2.2 open the switching transistor VT5, allowing the operation of the transmitter carrier generator. The transmitter is based on the device described in the brochure [3]. The generator is assembled on a transistor VT1 and stabilized by a quartz resonator ZQ1. A modulating signal with a frequency of 1024 Hz is applied to the VD1 varicap. Modulation - narrowband. The deviation within a small range is changed by the coil trimmer L1.

Fluctuations in the operating frequency of the generator highlights the oscillatory circuit L2C4. Through the coupling coil L3, the signal is fed to the input of the buffer resonant amplifier on the transistor VT2, operating in mode C. The load of the transistor is the circuit L4C6. Through the capacitor C8, the amplified signal is connected to the input of the power amplifier, which is made on two parallel-connected transistors VT3 and VT4. operating also in mode C. The output signal of the amplifier through the coupling capacitor C13. filter C14 L6 C15 L7 C16 and connector X1 goes to the transmitting antenna directly or via a cable with a characteristic impedance of 50 ohms.

The transmitter switches to continuous radiation mode when security sensors are triggered, closing the cathode of the VD3 diode to the car body. If it is necessary to decouple the sensors from each other, several such diodes should be installed, the anode of which should be connected to the collector of the VT5 transistor. If any sensors generate a high-level signal at the time of operation, the output of each of them is connected to the base of the VT5 transistor through a series-connected resistor with a resistance of 20 ... 33 kOhm and any silicon low-power diode (cathode to the base).

The circuit of the radio watchman receiver is shown in fig. 3. The high-frequency part is assembled according to the traditional scheme. The signal received by the WA1 antenna is highlighted by the input circuit L2C3. Diodes VD1 and VD2 are used to protect the input of the RF amplifier with a large input signal amplitude. The RF amplifier is assembled according to a cascode circuit on field-effect transistors VT1 and VT2. The load of the amplifier is the circuit L3C4.

car radio watchman
(click to enlarge)

The mixer is made on the DA1 chip. It also performs the functions of a local oscillator, the frequency of which is stabilized by a ZQ1 quartz resonator. The resonator frequency can be higher or lower than the transmitter frequency at 465 kHz. those. either 26480. or 27410 kHz. From the load of the mixer - resistor R4 - the IF signal is fed to the piezoceramic filter of the IF ZQ2. providing the necessary selectivity of the receiver. The DA2 chip performs signal amplification, clipping, and frequency detection. The resonant circuit C14L5 of the frequency detector is tuned to a frequency of 465 kHz.

The demodulated signal with a frequency of 1024 Hz is fed to the inputs of the comparator DA3 through two integrating circuits that differ in the value of the time constant. The direct input is signaled through the R7C21 circuit. almost completely suppressing the useful signal, and this signal comes to the inverse signal through the R8C22 circuit with almost no attenuation.

Such a node is a bandpass filter. At a frequency of 1024 Hz, it generates an output pulse sequence that is close to a "meander" in shape, and input signals with a frequency that differs significantly from 1024 Hz. almost never get out.

From the output of the comparator DA3, the signal is fed to the input of the digital node. The rhythm of its work is set by the generator on the DDI chip. whose frequency is stabilized the same. as in the transmitter, with a quartz resonator at a frequency of 32768 Hz. The output pulses of the generator with a frequency of 32768 Hz from the output K are fed to the CP input of the counter DD2.1 of the frequency control channel, and with a frequency of 1 Hz From the output 15 of the counter of the DDI chip - to the CP input of the counter DD2.2 and the CN input of the counter DD7 of the time interval control channel .

The DD2.1 counter generates pulses with a duty cycle of 2. The DD3 counter is a five-bit shift register, which, when output 2 is connected to input D0, divides the pulse frequency by four [4]. At the same time, at outputs 1 - 4, it generates signals of the "meander" type with a phase shift of 0, 90, 180 and 270 °.

These four signals are fed to the lower circuit inputs of the elements DD4.1 - DD4.4, and the output signal of the comparator DA3 is applied to the upper inputs, connected together. In the absence of a useful signal at the input of the receiver, a noise voltage acts at the output of the comparator. After mixing in the elements DD4.1 - DD4.4 with the output signals of the counter DD3, the noise is averaged by the integrating circuit R12C26. R13C27. R14C28. R15C29. As a result, the voltage across capacitors C26 - C29 is approximately half the supply voltage. At the input of the Schmitt trigger DD5.1, taking into account the drop on the diodes VD3 - VD6 and resistor R17, the voltage exceeds the upper switching threshold of the trigger, so its output will be a low logic level.

When a voltage with a frequency of 1024 Hz appears at the output of the comparator, it is multiplied by the elements DD4.1 - DD4.4 with the output signals of the counter DD3. If the phases of the signals at the inputs of any of these elements coincide, its output will be low, with antiphase signals it will be high, and with close phases there will be high duty cycle pulses, and the average voltage of these pulses is close to zero.

Therefore, approximately 0,5 s after the start of receiving the useful signal, one of the capacitors C26 - C29, corresponding to that element of the DD4 microcircuit. the phases of the input signals of which are closest, is discharged almost to zero. The voltage at the input of the Schmitt trigger DD5.1 ​​becomes lower than the lower switching threshold, and a high level appears at its output.

After about 0.5 s after the reception of the useful signal on the capacitors C26 - C29, a voltage close to half the supply voltage is again set, and the Schmitt trigger DD5.1 ​​goes into its original state. Thus, high-level pulses are formed at its output, approximately corresponding in duration to the input and delayed relative to it by 0.5 s. The HL1 LED flashes for 1 s, indicating the presence of a useful signal in the WA1 antenna. Negative OS through the resistor R19 somewhat reduces the width of the "hysteresis" loop of the Schmitt trigger. The passband width of the peculiar filter mentioned above is about 2 Hz, and when the modulation frequency goes beyond 1023 ... 1025 Hz, the Schmitt trigger DD5.1 ​​will not work.

Consider how the digital processing unit acts after switching on when receiving signal packages with a frequency of 1024 Hz and a repetition period of 16 s. The C32R21 circuit differentiates the front of the pulse generated at the output of element DD5.1. A short pulse of positive polarity - we will call it a control pulse (diagram 1 in Fig. 4) - is fed to the input R of the DDI counters. DD2.1. DD2.2. DD7. and also through the inverter DD6.2 to the input R of the trigger, assembled on the elements DD5.2 and DD5.3. setting the trigger to zero. This short pulse also passes through the elements DD6.3 and DD6.4 at a low level at the outputs 8 and 9 of the counter DD7 and the input S sets the trigger DD5.2. DD5.3 to a single state, in which the output of the element DD5.3 is a high logic level.

The pulse at the input S of the trigger has a duration greater. than at input R due to the action of the R18VD8C33 circuit. therefore, after the decay of the pulse, the trigger remains in a single state, keeping the element DD5.4 open. Since the upper input of this element from the output 8 of the counter DD2.1 receives pulses of the "meander" type with a frequency of 2048 Hz. a continuous beep sounds. Pulses with a frequency of 1 Hz come from the output 15 of the counter DD1 to the input CP of the counter DD2.2 and CN - DD7 (Fig. 2). The first of them considers these pulses by their decline, the second is blocked by a high level coming to the input of the CP from the output of the inverter DD6.1.

After 8 s, a high level appears at the output 8 of the counter DD2.2 (diagram 3). It stops and self-blocks the counter DD2.2. The counter can exit this state only after the zeroing pulse arrives at its input R. The signal from the output of the counter DD2.2 after inversion element DD6.1 allows the counter DD7, counting second pulses on their edge. After another 7,5 s, a high level appears at output 8 of this counter.

Thus, after 15,5 s after the appearance of the control pulse, a high level will appear at the lower input of the DD6.3 element according to the circuit, which is held for 1 s (Fig. 4). if during this time the input mode of the counter DD7 does not change.

When the next control pulse appears (16 s after the previous one), it switches the trigger DD5.2 to the zero state. DD5.3 and the sound signal stops. The impulse does not pass through the elements DD6.3, DD6.4. since the lower input of the element DD6.3 is high.

At the time of arrival of the control pulse, all counters, including DD7. are reset, however, at the lower input of the DD6.3 element, due to the action of the VD7R16C30 circuit, the change of a high level to a low level is delayed by about 200 μs. This guarantees the prohibition of the passage of a short control pulse (its duration is about 30 μs) to the input S of the trigger DD5.2. DD5.3. Therefore, when control pulses arrive, the trigger remains in the zero state and the signal does not sound. The described process is illustrated in fig. 4 solid lines.

If the next control pulse does not arrive after 16 ± 0,5 s, the device will operate as follows. as shown in fig. 4 dotted lines. High level. appeared after 16.5 s at the output 9 of the counter DD7. will set the trigger DD5.2. DD5.3 to the single state and the buzzer will sound. It will stop only when two pulses arrive at the receiver with an interval of 16 s between them.

The signal will also sound if the pulse appears earlier than 15,5 s after the previous one, since there will be no prohibition from the output 8 of the counter DD7 on its passage through the element DD6.3.

Thus, with the systematic arrival of signals with a modulation frequency of 1024 Hz and a period of 16 s, the system is in standby mode, the HL1 LED on its front panel flashes, indicating the health of the radio guard as a whole and the passage of radio signals. At any deviation from the specified rhythm, a signal starts to sound. The continuous glow of the HL1 LED means that some kind of security sensor is triggered, and the absence of glow means the transmitter stops working or the radio waves pass below the permissible level.

The transmitter is assembled on a printed circuit board made of double-sided foil fiberglass 1.5 mm thick. The drawing of the board is shown in fig. 5. On the side of the components, the foil is retained and serves as a common wire. Some of the leads are soldered to a common wire without holes. For the rest of the leads, through holes are drilled and countersinked from the side of the common wire. All solder points to the common wire are marked with crosses in the drawing. The holes for the "grounded" pins of the microcircuits do not need to be countersunk.

car radio watchman

Tinned pins with a diameter of 1 mm are pressed and soldered into the holes at the connection points of the board with the antenna connector X1, the power supply, and the sensors. It is convenient to use contacts from the 2PM connector as pins.

Transistors VT3 and VT4 are soldered on the side of the printed conductors, the conclusions must first be bent at a right angle. During the final assembly of the transmitter, the transistors are screwed to the metal casing of the device, which serves as a heat sink for them. They are isolated from the casing with thin mica gaskets.

The transmitter uses MT and MLT resistors, KM-5 and KM-6 capacitors. The KT315V transistor can be replaced with any silicon low-power n-p-n structure, and the KT368A transistor can be replaced with any of the KT316, KT325 series. Instead of KT646A, transistors of the KT603 and KT608 series are suitable, but you will have to overcome the difficulties of heat removal.

Diodes VD2 and VD3 - any low-power silicon. Varicap KB110A can be replaced by KB109, KB124, D901 with any letter index. Quartz resonator ZQ1 - standard, in a flattened metal case, and ZQ2 - in a cylindrical miniature case, from a watch.

Coils L1, L2L3 and L4 are wound turn to turn on three polystyrene frames with a diameter of 5 mm. equipped with carbonyl iron trimmers. Coil L1 contains 25 turns of PEV-2 0.25 wire. coils L2, L4 - 12 turns, and L3 - 3 turns of the same wire. Coil L3 is wound on top of L2. a L4 has a branch from the third from the top according to the coil scheme.

The inductor L5 is wound on a ring of size K10x6x3 made of 600NN ferrite. The winding contains 15 turns of wire PEV-2 0,15. Coils L6 and L7 are frameless, wound round to round on a mandrel with a diameter of 8 mm and contain 5 and 9 turns of wire PEV-2 0,8, respectively.

The transmitter is mounted in a metal box measuring 110x60x45 mm. A power switch (SA1), a high-frequency connector SR-50-73FV (X1) and a four-pin 2PM connector (not shown in the diagram in Fig. 1) for connecting a power source and sensors are installed on the walls of the case.

The electrical circuit of a small-sized whip spiral antenna of normal radiation [3]. designed for joint operation with a transmitter is shown in Fig. 6a, and its design is shown in Fig. 6b. A small plastic box (its dimensions are not critical) is fixed on the body of the cable block of the SR-50-73FV connector, into which the LC circuit is installed. consisting of a coil L1 and a tuning capacitor C1 with an air dielectric.

car radio watchman

Coil L1 is wound with a pitch of 2 mm with silver-plated copper wire with a diameter of 1 mm on a ceramic frame with a diameter of 10 mm. The number of turns is 15. The locations of the taps are determined when the system is being set up. Capacitor C1 - 1KPVM.

The extension coil L2 is wound coil by coil on a frame with a diameter of 6 mm made of organic glass. It contains 130 turns of PEV-2 0.15 wire. At the ends of the frame, two brass pins are fixed on the thread. The lower end of the lower pin according to the drawing is screwed into the hole of a brass bushing fixed on the upper wall of the plastic box.

The receiver is assembled on a printed circuit board made of double-sided foil fiberglass 1.5 mm thick. The board drawing is shown in fig. 7. Same. as on the transmitter board, under the elements of the high-frequency part of the receiver, the foil is preserved and plays the role of a common wire. The foil frame around the digital node has also been preserved. To connect the board to the antenna, the BF1 sound emitter and the power supply connector, contact pins with a diameter of 1 mm are pressed and soldered into it, just like in the transmitter.

car radio watchman
(click to enlarge)

Note that a number of board mounting points related to the digital node need to be soldered on both sides of the board. At two points - they are not round, but square in the drawing - you must first insert short wire jumpers into the holes.

The receiver uses resistors MT and MLT; oxide capacitors - K53-19. the rest - KM-5 and KM-6. It is possible to use parts of other types. Transistors KPZ0ZB can be replaced with one double-gate. for example, KP350B. Diodes VD1 and VD2 - any silicon high-frequency or pulse, the rest - low-power silicon. Instead of FP1P 1-060.1, other piezo filters for this frequency are also suitable, having a bandwidth of at least 3 kHz, for example. FP1P-60. FP1P-61. Quartz resonator ZQ3 - miniature, in a cylindrical case.

Coils L1L2 and L3L4 are wound on two identical polystyrene frames with a diameter of 5 mm, equipped with carbonyl iron trimmers. Coils L2 and L3 each contain 18 turns of PEV-2 0.33 wire. winding coil to coil. The communication coils L1 and L4 - 3 turns of PEVSHO 0,2 wire each - are wound over their loop ones from the side of the grounded output of the coil L2 and from the side of the output of the coil L3 connected to the positive power wire. The L5 coil is used industrially manufactured with an inductance of 120 μH with a trimmer. It can be wound independently in the SB-9a armored magnetic circuit. number of turns - 80. wire - PEV-2 0.1.

The board is installed in a plastic case from a pocket receiver with dimensions of 140x80x40 mm. The antenna is telescopic with a length of about 50 cm. An external power supply unit with an output voltage of 12 V was used to power the receiver, supplemented by a voltage stabilizer on the KR142EN8A chip and an output oxide capacitor with a capacity of 10 μF for a voltage of at least 16 V. To reduce multiplicative interference, both outputs of the secondary winding of the network block transformer are connected to its output negative wire through ceramic capacitors with a capacity of 0,1 μF. The battery 7D-0.115-U1.1 can be used for autonomous power supply of the receiver.

The system must be assembled and adjusted in a certain order. First, the digital part is assembled both in the transmitter and in the receiver, but without the resistor R17 in the receiver, and resistors R4 are additionally installed in the transmitter. R5 and R7. The power supply circuits of the transmitter and receiver are connected, the collector of the transistor VT5 of the transmitter is connected to the inputs of the receiver element DD5.1.

When the supply voltage is applied, the sound signal may or may not turn on, however, with the arrival of the first transmitter pulse, the HL1 LED should flash for a short time and the signal should sound (or continue to sound). After 16 s, the HL1 LED should flash again, and the signal should stop. Further, the LED should turn on for 1 s every 16 s. and the beeper - stay off.

Then, in the pause between pulses, the capacitor C31 of the receiver should be closed, which will simulate the transition of the transmitter to continuous mode. An alarm should sound immediately. Open the capacitor C31 and make sure that after passing two pulses from the transmitter (this can be clearly seen from the flashes of the HL1 LED), the sound signal stops. Disconnect the inputs of the element DD5.1 ​​of the receiver from the collector of the transistor VT5 of the transmitter - no later than after 15 s, the signal should sound again.

Next, resistors R1 - R3 are installed in the transmitter. R14, and in the receiver - R7 - R9, R17, capacitors C21, C22 and comparator DA3. At the common point of the resistors R7 and R8 of the receiver, pulses with a frequency of 2 Hz are fed through the button from the common point of the resistors R3 and R1024 of the transmitter. When closing and opening the contacts of the button, the HL1 LED should turn on and off, respectively, with a short delay (it should be noticeable to the eye).

If the nodes do not work as described, faults should be sought, as usual, when setting up digital devices - check the operation of quartz oscillators, the correct frequency division in the counters and the formation of the corresponding signals, etc. If, when manipulating the button, a pulse signal with a frequency of 1024 Hz does not the LED turns on, the resistor R19 is selected and. possibly R20. For the convenience of the exact selection of the R19 resistor, it is "split" into two parts (and there are places for them on the board), which have a resistance ratio of 9:1.

After the complete assembly of the device, the radio channel setup should begin with the transmitter. The emitter and collector of the transistor VT5 are connected with a temporary jumper, and as an antenna equivalent, the transmitter output is loaded with a 51 Ohm resistor with a power of 2 W. At the time of tuning, transistors VT3 and VT4 must be installed on a plate duralumin or copper heat sink with dimensions of at least 100x60 mm

By applying a supply voltage to the transmitter and rotating the L2 coil trimmer, generation is achieved. At the same time, an RF voltage of 2 V should be present on the basis of the VT0,6 transistor. It is measured with a broadband oscilloscope or a high-frequency voltmeter. The buffer stage on the transistor VT2 is adjusted by rotating the trimmer of the coil L4 until the maximum amplitude is obtained on the collector of the transistor VT2 (at least 5 V). At the same time, on the basis of transistors VT3 and VT4 there must be a voltage of at least 2 V. By stretching and compressing the turns of the coils L6 and L7, they achieve the maximum voltage on the antenna equivalent - 10 ... 12 V. The transmitter setting is specified in the same order after it is installed in frame.

Then tune the transmitting antenna. In the middle of a metal plate (foiled fiberglass can also be used) with dimensions of at least 250x250 mm, a SR-50-73FV connector socket is installed and connected to the transmitter output with a cable that will connect the antenna to it on the car. Install the antenna with the male part of the connector into the female and turn on the transmitter to work in continuous mode. The measurement maximum is controlled by the field strength indicator. You can use a simple wavemeter [5] by connecting a small microammeter to its output.

The circuit L1C1 of the antenna is tuned to resonance for the maximum reading. Next, a tap is selected from the coil towards the transmitter (2 ... 3 turns) and towards the pin (6 ... 10 turns), also achieving the highest field strength. After installing the antenna in the car, the setting of the L1C1 circuit is clarified.

To establish the receiver, it is advisable to use a broadband oscilloscope. Work begins with an IF amplifier. A signal with a frequency of 465 kHz with a deviation of 3 kHz is fed to the input of the DA2 microcircuit (pin 13) and the L5C14 circuit is tuned by rotating the trimmer of the L5 coil until the best squareness and duty cycle of the pulses equal to two are obtained at the output of the DA2 microcircuit. If self-excitation of the DA2 microcircuit is detected, the L5 coil should be shunted with a low-power resistor with a resistance of 5..10 kOhm.

Then check the operation of the local oscillator. If necessary, capacitors C6 - C8 are selected until stable generation is obtained at the third mechanical harmonic of the quartz resonator Z01.

Next, check the voltage at the source of the transistor VT2. it should be within 0,3 ... 0,5 V. By applying a signal with an operating frequency to the input of the receiver, by rotating the trimmers of the coils of the L2C3 and L3C4 circuits, tune the circuits into resonance, focusing on obtaining the maximum sensitivity of the receiver (about 0,5 μV) .

In the absence of a signal generator, it can be replaced by a tuned transmitter without an antenna by loading it with the 51 ohm resistor mentioned above. First, the transmitter is located next to the receiver, and as it is adjusted, the transmitter is moved away to the maximum distance, controlling the signal reception on the oscilloscope connected to the output of the DA2 microcircuit, or by the glow of the HL1 LED.

The transmitter is quite economical - a fully charged car battery with a capacity of 55 Ah is enough for three months of its continuous operation in standby mode.

The described radio guard has been in operation for more than three years and once already helped prevent intruders from entering the car.

A lot of useful information on the construction of a radio channel of a car watchdog and on various design options for transmitter and receiver antennas is contained in publications [1,6 - 8].

The transmitter is assembled on a printed circuit board made of double-sided foil fiberglass 1.5 mm thick. The drawing of the board is shown in fig. 5. On the side of the components, the foil is retained and serves as a common wire. Some of the leads are soldered to a common wire without holes. For the rest of the leads, through holes are drilled and countersinked from the side of the common wire. All solder points to the common wire are marked with crosses in the drawing. The holes for the "grounded" pins of the microcircuits do not need to be countersunk.

Tinned pins with a diameter of 1 mm are pressed and soldered into the holes at the connection points of the board with the antenna connector X1, the power supply, and the sensors. It is convenient to use contacts from the 2PM connector as pins.

Transistors VT3 and VT4 are soldered on the side of the printed conductors, the conclusions must first be bent at a right angle. During the final assembly of the transmitter, the transistors are screwed to the metal casing of the device, which serves as a heat sink for them. They are isolated from the casing with thin mica gaskets.

The transmitter uses MT and MLT resistors, KM-5 and KM-6 capacitors. The KT315V transistor can be replaced with any silicon low-power n-p-n structure, and the KT368A transistor can be replaced with any of the KT316, KT325 series. Instead of KT646A, transistors of the KT603 and KT608 series are suitable, but you will have to overcome the difficulties of heat removal.

Diodes VD2 and VD3 - any low-power silicon. Varicap KB110A can be replaced by KB109, KB124, D901 with any letter index. Quartz resonator ZQ1 - standard, in a flattened metal case, and ZQ2 - in a cylindrical miniature case, from a watch.

Coils L1, L2L3 and L4 are wound turn to turn on three polystyrene frames with a diameter of 5 mm. equipped with carbonyl iron trimmers. Coil L1 contains 25 turns of PEV-2 0.25 wire. coils L2, L4 - 12 turns, and L3 - 3 turns of the same wire. Coil L3 is wound on top of L2. a L4 has a branch from the third from the top according to the coil scheme.

The inductor L5 is wound on a ring of size K10x6x3 made of 600NN ferrite. The winding contains 15 turns of wire PEV-2 0,15. Coils L6 and L7 are frameless, wound round to round on a mandrel with a diameter of 8 mm and contain 5 and 9 turns of wire PEV-2 0,8, respectively.

The transmitter is mounted in a metal box measuring 110x60x45 mm. A power switch (SA1), a high-frequency connector SR-50-73FV (X1) and a four-pin 2PM connector (not shown in the diagram in Fig. 1) for connecting a power source and sensors are installed on the walls of the case.

The electrical circuit of a small-sized whip spiral antenna of normal radiation [3]. designed for joint operation with a transmitter is shown in Fig. 6a, and its design is shown in Fig. 6b. A small plastic box (its dimensions are not critical) is fixed on the body of the cable block of the SR-50-73FV connector, into which the LC circuit is installed. consisting of a coil L1 and a tuning capacitor C1 with an air dielectric.

Coil L1 is wound with a pitch of 2 mm with silver-plated copper wire with a diameter of 1 mm on a ceramic frame with a diameter of 10 mm. The number of turns is 15. The locations of the taps are determined when the system is being set up. Capacitor C1 - 1KPVM.

The extension coil L2 is wound coil by coil on a frame with a diameter of 6 mm made of organic glass. It contains 130 turns of PEV-2 0.15 wire. At the ends of the frame, two brass pins are fixed on the thread. The lower end of the lower pin according to the drawing is screwed into the hole of a brass bushing fixed on the upper wall of the plastic box.

The receiver is assembled on a printed circuit board made of double-sided foil fiberglass 1.5 mm thick. The board drawing is shown in fig. 7. Same. as on the transmitter board, under the elements of the high-frequency part of the receiver, the foil is preserved and plays the role of a common wire. The foil frame around the digital node has also been preserved. To connect the board to the antenna, the BF1 sound emitter and the power supply connector, contact pins with a diameter of 1 mm are pressed and soldered into it, just like in the transmitter.

Note that a number of board mounting points related to the digital node need to be soldered on both sides of the board. At two points - they are not round, but square in the drawing - you must first insert short wire jumpers into the holes.

The receiver uses resistors MT and MLT; oxide capacitors - K53-19. the rest - KM-5 and KM-6. It is possible to use parts of other types. Transistors KPZ0ZB can be replaced with one double-gate. for example, KP350B. Diodes VD1 and VD2 - any silicon high-frequency or pulse, the rest - low-power silicon. Instead of FP1P 1-060.1, other piezo filters for this frequency are also suitable, having a bandwidth of at least 3 kHz, for example. FP1P-60. FP1P-61. Quartz resonator ZQ3 - miniature, in a cylindrical case.

Coils L1L2 and L3L4 are wound on two identical polystyrene frames with a diameter of 5 mm, equipped with carbonyl iron trimmers. Coils L2 and L3 each contain 18 turns of PEV-2 0.33 wire. winding coil to coil. The communication coils L1 and L4 - 3 turns of PEVSHO 0,2 wire each - are wound over their loop ones from the side of the grounded output of the coil L2 and from the side of the output of the coil L3 connected to the positive power wire. The L5 coil is used industrially manufactured with an inductance of 120 μH with a trimmer. It can be wound independently in the SB-9a armored magnetic circuit. number of turns - 80. wire - PEV-2 0.1.

The board is installed in a plastic case from a pocket receiver with dimensions of 140x80x40 mm. The antenna is telescopic with a length of about 50 cm. An external power supply unit with an output voltage of 12 V was used to power the receiver, supplemented by a voltage stabilizer on the KR142EN8A chip and an output oxide capacitor with a capacity of 10 μF for a voltage of at least 16 V. To reduce multiplicative interference, both outputs of the secondary winding of the network block transformer are connected to its output negative wire through ceramic capacitors with a capacity of 0,1 μF. The battery 7D-0.115-U1.1 can be used for autonomous power supply of the receiver.

The system must be assembled and adjusted in a certain order. First, the digital part is assembled both in the transmitter and in the receiver, but without the resistor R17 in the receiver, and resistors R4 are additionally installed in the transmitter. R5 and R7. The power supply circuits of the transmitter and receiver are connected, the collector of the transistor VT5 of the transmitter is connected to the inputs of the receiver element DD5.1.

When the supply voltage is applied, the sound signal may or may not turn on, however, with the arrival of the first transmitter pulse, the HL1 LED should flash for a short time and the signal should sound (or continue to sound). After 16 s, the HL1 LED should flash again, and the signal should stop. Further, the LED should turn on for 1 s every 16 s. and the beeper - stay off.

Then, in the pause between pulses, the capacitor C31 of the receiver should be closed, which will simulate the transition of the transmitter to continuous mode. An alarm should sound immediately. Open the capacitor C31 and make sure that after passing two pulses from the transmitter (this can be clearly seen from the flashes of the HL1 LED), the sound signal stops. Disconnect the inputs of the element DD5.1 ​​of the receiver from the collector of the transistor VT5 of the transmitter - no later than after 15 s, the signal should sound again.

Next, resistors R1 - R3 are installed in the transmitter. R14, and in the receiver - R7 - R9, R17, capacitors C21, C22 and comparator DA3. At the common point of the resistors R7 and R8 of the receiver, pulses with a frequency of 2 Hz are fed through the button from the common point of the resistors R3 and R1024 of the transmitter. When closing and opening the contacts of the button, the HL1 LED should turn on and off, respectively, with a short delay (it should be noticeable to the eye).

If the nodes do not work as described, faults should be sought, as usual, when setting up digital devices - check the operation of quartz oscillators, the correct frequency division in the counters and the formation of the corresponding signals, etc. If, when manipulating the button, a pulse signal with a frequency of 1024 Hz does not the LED turns on, the resistor R19 is selected and. possibly R20. For the convenience of the exact selection of the R19 resistor, it is "split" into two parts (and there are places for them on the board), which have a resistance ratio of 9:1.

After the complete assembly of the device, the radio channel setup should begin with the transmitter. The emitter and collector of the transistor VT5 are connected with a temporary jumper, and as an antenna equivalent, the transmitter output is loaded with a 51 Ohm resistor with a power of 2 W. At the time of tuning, transistors VT3 and VT4 must be installed on a plate duralumin or copper heat sink with dimensions of at least 100x60 mm

By applying a supply voltage to the transmitter and rotating the L2 coil trimmer, generation is achieved. At the same time, an RF voltage of 2 V should be present on the basis of the VT0,6 transistor. It is measured with a broadband oscilloscope or a high-frequency voltmeter. The buffer stage on the transistor VT2 is adjusted by rotating the trimmer of the coil L4 until the maximum amplitude is obtained on the collector of the transistor VT2 (at least 5 V). At the same time, on the basis of transistors VT3 and VT4 there must be a voltage of at least 2 V. By stretching and compressing the turns of the coils L6 and L7, they achieve the maximum voltage on the antenna equivalent - 10 ... 12 V. The transmitter setting is specified in the same order after it is installed in frame.

Then tune the transmitting antenna. In the middle of a metal plate (foiled fiberglass can also be used) with dimensions of at least 250x250 mm, a SR-50-73FV connector socket is installed and connected to the transmitter output with a cable that will connect the antenna to it on the car. Install the antenna with the male part of the connector into the female and turn on the transmitter to work in continuous mode. The measurement maximum is controlled by the field strength indicator. You can use a simple wavemeter [5] by connecting a small microammeter to its output.

The circuit L1C1 of the antenna is tuned to resonance for the maximum reading. Next, a tap is selected from the coil towards the transmitter (2 ... 3 turns) and towards the pin (6 ... 10 turns), also achieving the highest field strength. After installing the antenna in the car, the setting of the L1C1 circuit is clarified.

To establish the receiver, it is advisable to use a broadband oscilloscope. Work begins with an IF amplifier. A signal with a frequency of 465 kHz with a deviation of 3 kHz is fed to the input of the DA2 microcircuit (pin 13) and the L5C14 circuit is tuned by rotating the trimmer of the L5 coil until the best squareness and duty cycle of the pulses equal to two are obtained at the output of the DA2 microcircuit. If self-excitation of the DA2 microcircuit is detected, the L5 coil should be shunted with a low-power resistor with a resistance of 5..10 kOhm.

Then check the operation of the local oscillator. If necessary, capacitors C6 - C8 are selected until stable generation is obtained at the third mechanical harmonic of the quartz resonator Z01.

Next, check the voltage at the source of the transistor VT2. it should be within 0,3 ... 0,5 V. By applying a signal with an operating frequency to the input of the receiver, by rotating the trimmers of the coils of the L2C3 and L3C4 circuits, tune the circuits into resonance, focusing on obtaining the maximum sensitivity of the receiver (about 0,5 μV) .

In the absence of a signal generator, it can be replaced by a tuned transmitter without an antenna by loading it with the 51 ohm resistor mentioned above. First, the transmitter is located next to the receiver, and as it is adjusted, the transmitter is moved away to the maximum distance, controlling the signal reception on the oscilloscope connected to the output of the DA2 microcircuit, or by the glow of the HL1 LED.

The transmitter is quite economical - a fully charged car battery with a capacity of 55 Ah is enough for three months of its continuous operation in standby mode.

The described radio guard has been in operation for more than three years and once already helped prevent intruders from entering the car.

A lot of useful information on the construction of a radio channel of a car watchdog and on various design options for transmitter and receiver antennas is contained in publications [1,6 - 8].

Literature

  1. Vinogradov Yu. Radio channel of the burglar alarm. Transmission block. - Radio. 1995. No. 1. and. 37 - 40
  2. Alekseev S. The use of K176 series microcircuits. - Radio. 1985. No. 5. p. 36 - 40.
  3. Radio security devices. Minsk. NTC "Infotech". 1992. 12 p.
  4. Alekseev S. The use of microcircuits of the K5b series 1. - Radio. 1987. No. 1. p. 43 - 45.
  5. Golubev O. A simple wavemeter. - Radio. 1998. No. 10. p. 102.
  6. Vinogradov Yu. Radio channel of the burglar alarm. receiving block. - Radio. 1995, No. 4. p. 47-50.
  7. Vinogradov Yu. Disk antenna in the range of 27 MHz. - Radio. 1997. No. 2. p. 70.
  8. Vinogradov Yu. CB antenna on the window. - Radio, 1998. No. 4, p. 80.

Author: S. Biryukov, Moscow

See other articles Section Automobile. Security devices and alarms.

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