Radio remote security device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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A distinctive feature of the proposed design is that the alarm sounds not from the guarded car (at present, such an alarm only causes irritation to others), but from a portable radio receiver located at the owner of the car or next to him.

If necessary, external actuators can be connected to the receiver. The alarm signal can take any form acceptable to the owner of the protected object.

The device does not have a secret switch. It is not so easy to neutralize it: an alarm is generated not in case of detection of transmitter radiation, but in case of its disappearance. Therefore, the security device is triggered when the transmitter is turned off, when it is disabled (for example, with a stun gun), when interference is set, and, of course, when security sensors are triggered.

Consumer qualities (radius, applied code) can be significantly changed, both in the direction of expansion and in the direction of narrowing, depending on the task and the capabilities of the owner.

The device consists of a transmitter and receiver operating in the CB band.

Transmitter. The block diagram of the transmitter is shown in Fig.1. The master crystal oscillator 1 is controlled by the transmission signal generator 4 as follows.

1. If all security sensors are on standby, then generator 1 generates stable oscillations for 1 s. These oscillations are modulated in amplitude in the modulator 2 with a frequency of 1024 Hz, amplified in the power amplifier 3 and fed into the antenna. This is followed by a pause of 9 s, and the transmitter is turned on again for 1 s. If at least one sensor is triggered, the transmitter is blocked for 39 seconds. During this time, two second messages disappear, which is a sign of an emergency condition.

2. If the car is moving and it has movement, roll or acoustic sensors installed, then the transmitter is permanently switched off and returns to working state 39 seconds after the last sensor was triggered (for example, after stopping the car and closing the doors).

The transmitter is powered by a 12 V DC source. When installed in a vehicle, the transmitter consumes an average current of 40 mA (120 mA in transmit mode and 30 mA in pause mode).

The schematic diagram of the transmitter is shown in Fig.2. The master oscillator is assembled according to the traditional scheme with a quartz resonator Z2 on a transistor VT2, the power circuit of which is turned on by a key on a transistor VT3. Resistor R13 limits the base current of the transistor VT3, and R18 contributes to reliable closing at log. "0" at pin 2 of counter DD4. Capacitors C3, C8, C11 blocking. The collector load of the generator is the resonant circuit L1, C9, operating in the range of 10 m (CB band).

(click to enlarge)

The carrier frequency signal through the capacitor C10 is fed to the base of the transistor VT4, which acts as a modulator. A low-frequency signal of 2 Hz is also supplied here through the L1024 choke.

Amplitude-modulated carrier is allocated on the loop with incomplete inclusion of L3. Further, the transmitter signal is fed through a decoupling capacitor C13 to a power amplifier assembled on a transistor VT5, the load of which is an antenna with extension circuits C16L5, C18L6.

The sensor state analyzer consists of two logic elements DD2.1 and DD2.2. The emergency state of the sensors leads to the appearance of a log. "1" at pin 9 DD2.2. Since the logical elements DD2 have an output with inversion, this allows you to connect sensors with any logic of operation (either "0" or "1" in an emergency state, in the case of "0" the sensors are connected to the inputs DD2.2, in the case of "1" - to the inputs DD2.1).

The diagram shows the connection of three sensors, but their number is unlimited, Figure 3 shows how additional sensors can be connected through diodes.

Zener diodes VD1-VD3 at the inputs of logic elements protect them from voltages above the supply voltage and from surges of reverse polarity.

The transmit signal shaper consists of a crystal oscillator and a frequency divider on a DD1 chip, a DD3 inhibit trigger and a DD4 pulse counter. In this circuit, "clock" quartz (32768 Hz) is used.

When the power is turned on due to the elements C2, R10, the trigger DD3 is set to a state where its output is 12 log "0". In this case, the counter DD4 counts the second pulses available at pin 4 DD1, and one such pulse out of 3 is allocated to its pins 2 and 10. To pin 3 DD4 through the inverter DD2.3, the VD4 LED is connected, indicating the on state of the device, and from the output 2, the control signal is fed to the base of the transistor VT3, which turns on the power of the transmitter.

From pin 11 DD1 through the emitter follower VT1, a signal with a frequency of 1024 Hz is fed to the modulator. In this case, the log. "1" at pin 13 DD3 prohibits the operation of the minute pulse shaper. If at least a short-term pulse comes from the analyzer of the state of the sensors to the trigger DD3, the trigger changes its state to the opposite. In this case, the counter DD4 at the input R is reset, a log "2" appears on its outputs 3 and 0, which turns off the transmitter and the LED. At this time, the counter of minute pulses (pin 9 DD1) starts working, after 39 s a positive drop will appear at the output M of this counter, and the trigger DD3 will return to its original state. Thus, with a short-term operation of the sensors, the transmitter becomes silent for 39 seconds, and if the alarm signal from the sensor is repeated, the transmitter will not work at all.

Thanks to this operating logic, the transmitter does not require a hidden switch. The use of digital reading of time intervals ensures high stability of parameters during operation.

Receiver. The block diagram of the receiver is shown in Fig.4. It is assembled according to a superheterodyne circuit with quartz frequency stabilization, therefore it does not have any tuning elements.

(click to enlarge)

The receiver includes: a high-frequency amplifier (RF) 1, a local oscillator 2, a mixer 3, an intermediate frequency amplifier (IF) 4, a detector 5, a frequency filter 1024 Hz 6, a low-frequency signal rectifier 7, an adaptation circuit 8, a comparator 9 and an indication circuit and alarms. The comparator, depending on the signal level at its input, generates voltages close to the logic levels of CMOS microcircuits, which allows the indication and signaling device to perform the following functions:

• indication of the presence of reception of transmitter signals;
• sound signaling of the loss of reception of more than one sending of the transmitter signal;
• light signaling of the fact of loss of reception.

The receiver can operate in one of two alarm modes: permanent alarm mode (the alarm sounds continuously) or economy mode (only one series of alarm sounds is generated).

The circuit diagram of the receiver is shown in Fig.5.

(click to enlarge)

(click to enlarge)

The radio frequency amplifier (URCH) is assembled on a field-effect transistor VT1. It is loaded on a resonant circuit with transformer connection L3, L4, C5. A high-Q circuit L2, C2 is also included at the input of the URF to increase the selectivity of the receiver.

The local oscillator is assembled on a transistor VT3 according to a well-known scheme with stabilization of the supply voltage by the stabilizer R3, VD2. The cascade on the transistor VT2 performs the function of a mixer. Through a 465 kHz piezoelectric filter, the signal is fed to the VT4-VT6 cascode amplifier, which is the IF. The amplitude detector is made on germanium diodes VD3, VD4.

The thus received signal with a frequency of 1024 Hz is fed through the coupling capacitor C16 to an active filter tuned to this frequency. This filter is assembled according to the double T-bridge circuit on frequency-setting elements C18-C23 and R29, R30, R32, R33, as well as transistors VT7, VT8. From the filter output, the signal through the capacitor C24 is fed to the rectifier with voltage doubling VD5, VD6.

Adaptation scheme. When voltage appears on capacitor C27, the noise suppression capacitor C29 is charged. Through the limiting resistor R36 and capacitor C31, voltage is applied to the non-inverting input of the comparator DA1. With prolonged exposure to the input signal, for example, strong industrial interference, the capacitor C31 is charged, the control current stops, and the comparator "turns off". However, when a useful signal appears, it will add up to the background one, and the voltage at C31 will increase, which will cause the comparator to fire.

Capacitor C32 eliminates the passage of high-frequency emissions to the input of the comparator. Due to the large inertia, such a circuit does not "hear" a useful signal for some time after the cessation of exposure to strong interference, since the time constant of the discharge of C31 is 1-3 periods of the transmitter signal. However, it allows you to significantly increase the reception range due to the fact that the information is the difference from the minimum level at the moment to the maximum, and not the absolute value of the signal itself.

A feature of the comparator is its unipolar power supply. The input potentials are set by resistors R37, R38, R27, R35, R39, R40. The circuit also does not have negative feedback, which determines the formation of logic levels at pin 6 of DA1.

Scheme of indication and signaling.

When the power is turned on by the circuit R45, R46, C35, the counter DD2 and triggers DD3 are set to "0". From the output of the comparator, positive pulses with a duration of 1 s and a duty cycle of 10 are fed to the input DD1.2 (pin 12), and after inversion - to the input DD1.3 (pin 9). From the output of this element (pin 10), positive pulses through the resistor R48 are fed to the input R of the counter DD2 (pin 9), setting it to its original state.

With normal reception of transmitter signals, the counter does not have time to overflow, while at pin 9 DD4.1 - log. "0", and the sound signal does not pass to the emitter. If in this state of the circuit you press the button SB3 "On Ind.", then the VD1 LED flashes at a frequency of 1 Hz and a duty cycle of 4, since pulses with a period of 2 and 3 s are applied to pins 4.2 and 0,5 of DD1, respectively. LED VD1 flashes at the moment of receiving signals from the transmitter, and the duration of the glow of this LED at a reception level close to the minimum possible decreases until it turns off completely, which indicates that the receiver is in the area of ​​uncertain reception.

Resistor R46 improves the reliability of SB1 by limiting the surge current through its contacts. This button resets the circuit.

If for some reason the transmitter signal at the output of the comparator DA1 disappears, then the counter DD2 overflows, and a log "10" appears at its output 19,5 1 s after the arrival of the last pulse, which, at pin 9, allows the passage of intermittent (0,5, 1024 s) a 11 Hz signal from output 2 DD1 to the sound emitter BAXNUMX.

Light indication trigger DD3.2 overturns and generates a log. "0" on pins 4, 5 DD4.2. If you press SB3 in this state of the circuit, then the VD1 LED will glow constantly, signaling that the signal has disappeared, since the DD3.2 trigger can only be returned to its original state by pressing the SB1 button "Set Initial Status." or turning off the power of the receiver. Log. the level at pin 2 of DD3.2 can be used to turn on external actuators.

After the next 10 s after the overflow of the counter DD2, a log "10" appears on its output 0, which is inverted by DD1.1, and the differential on the counting input C trigger DD3.1 is transferred to the opposite state, the sound signal stops (log "0" at pin 9 DD4.1). At pin 12 (Q), a log "0" is formed. If the SA1 switch is set to the "Post" position, then after the next 19,5 s, the alarm will sound again for 10 s, and so on. If SA1 is set to "Once", then after the first 10 s of sound signaling from output 12 DD3.1, log."0" enters input 12 DD4.1, thereby prohibiting the passage of alarm signals to the emitter. The circuit can remain in this state indefinitely.

To prevent the counter from being set to its initial state by input pulses in the switch position SA1 "Once" from the output 12 DD3.1 through the diode VD8, a log "12" is sent to the output 1.2 DD0.

If the SA1 switch is set to the "Post" position, the audible alarm stops when a useful signal appears. However, this mode is wasteful if the receiver is powered from an independent source, since the audio signal requires more power than the entire receiver.

To stop the sound signal before the end of the cycle (20 sound packets), the SB2 button "Stop Sound Signal" is provided. Pressing it causes an "early" negative drop at pin 9 of DD2 (counter reset) and the sound signal stops until the next overflow of the counter, if switch SA1 is in the "Post" position, or until the circuit is reset with the SB1 button, if SA1 is in the " Razov".

Naturally, all settings return to their original state when the receiver is turned on again.

Construction and details. In the embodiment described above, the receiver was assembled on a 110×55 mm board, and a ready-made metal case with a board size of 75×135 mm and a very free installation was used for the transmitter. There are no requirements for the placement of elements, except for the case of increased transmitter power, in which case it is desirable to shield the elements of the sensor state analyzer and the transmission signal conditioner from the output stage and antenna.

There are no accuracy requirements for circuit details, except for elements of the comparator input circuits and 1024 Hz filter capacitors. Since these elements can significantly affect the stability of the entire device, it is better to use tantalum capacitors of the K52, K53-1, K53-4 or K53-14 types in these circuits. As a last resort, aluminum imported capacitors with the least leakage can be used.

The most delicate place is the 1024 Hz filter. The capacitances of its capacitors are selected by parallel, series or mixed connection, but they must be highly stable.

The frequencies of quartz resonators must be within the permitted range and provide an intermediate frequency (frequency difference) of 465 kHz.

Sensors can be both homemade and industrially manufactured. You can use the "limit switches" of doors and hoods available in the car.

A telephone capsule of the MSD510 type with a coil resistance of 10 ohms was used as the receiver's loudspeaker, but this is not the best option. For this purpose, you can use any sound emitter that is suitable in size, volume and price. The output amplifier can be anything, in this device it is assembled on a single VT10 transistor and takes up a minimum of space.

All inductors are wound on standard D5 mm frames with trimmer cores with PEL, PEV, PETV or other D0,2 ... 0,3 mm wire. The winding of all coils is ordinary, turn to turn. In the receiver: L1 - 18 turns; L2 - 15 turns with a tap from the 13th turn, counting from above; L3 - 15 turns; L4 - 2 turns; L5 - 10 turns with a tap from 0,5 turn, counting from above. Coils L3 and L4 are shielded. In the transmitter: L1 - 11 turns; L3 - 11 turns with taps from 1,5 and 5 turns, counting from above; L5 - 8 turns; L6 - 18 turns. Inductors L2 and L4 are standard or home-made, wound with D0,15 mm wire on MLT-0,5 resistors with a rating of at least 470 kOhm in several layers.

Setting. The digital part of the transmitter, which implements the functions of the analyzer of the state of the sensors of the transmit signal shaper, does not need to be configured, except for the possible installation of additional capacitors shown in Fig. 3. Enabling them reduces the performance of the device. The setting of the transmitter itself is well known and has no special features.

In the absence of special measuring instruments, the L1C9 circuit is tuned to the condition for the best excitation of the master oscillator, which can be detected by connecting a conventional tester in the AC voltage measurement mode at the minimum limit to the base of the transistor VT2. The output stage coils are tuned for maximum radiated power by placing the tester wire in close proximity to the antenna.

The antenna itself is a piece of mounting wire about 1,25 m long.

To fine-tune the transmitter, the antenna must be installed in the place allotted for it and finally adjusted to the maximum radiation. In the absence of appropriate instruments, the transmitter is adjusted to the maximum receiving range.

The receiver itself is a classic superheterodyne receiver circuit with a fixed tuning, stabilized by quartz. The generation frequency of the crystal oscillator depends to some extent on the frequency of the L5C10 resonant circuit. Therefore, it is better to set the exact frequency difference equal to the intermediate frequency to which the IF filter is tuned in the receiver rather than in the transmitter. Tuning should begin with the antenna circuits L1C1 and L2C2 according to the transmitter signal. The length of the receiving antenna can be chosen shorter than in the transmitter, taking into account the convenience of use. After that, the local oscillator is tuned for the best approximation to the intermediate frequency. The receiver is tuned for the maximum receiving range, but to simplify tuning, the transmitter power can be reduced by turning off the antenna.

The most subtle thing is the 1024 Hz filter setting. If there is no device that can output a signal of this frequency with an accuracy of 10 Hz, you can use the signal from the DD2 chip (pin 11), which has a frequency of 1024 Hz. The filter setting is reduced to the selection of capacitors C18, C19, C22, C23, and their capacities must be the same. Resistor R29 regulates the quality factor of the filter, which should be equal to 4.

Setting the comparator is reduced to the selection of the resistor R56 so that the comparator does not work when the temperature changes, with random interference.

The digital part of the receiver does not require tuning.

Author: V.M.Paley

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