Radio security system for shells. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Automobile. Security devices and alarms

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Car owners are trying in every way to protect their cars from intruders. A car parked in the yard at night can become easy prey, especially since it is supposed to introduce a law on liability for disturbing silence at night, limiting the use of alarms. A more reliable way to protect the car in the yard is to install a metal awning ("shells"). The proposed system informs the owner by radio about the fact of penetration into the "shell".

The alarm signal can be transmitted in one of the channels of the civil communication range and received by the simplest CB radio station - Ural-R, Laspi, etc. It will only be necessary to make a transmitter that generates this alarm signal at the frequency of such a station.

The schematic diagram of the transmitter is shown in fig. 1. The master oscillator, assembled on the transistor VT2, is excited at the frequency of the quartz resonator ZQ1, which coincides with the operating frequency of the receiving station. Since almost all radio stations in this range operate with frequency modulation (the carrier is frequency modulated), a VD1 varicap and an L4 coil are introduced into the ZQ1 circuit. By changing the voltage on the varicap, you can change the frequency of the generated signal within 2...3 kHz from the center frequency.

(click to enlarge)

Transistors VT3 and VT4 perform the function of a power amplifier. The L2C8C9 and L5C12C13C14 circuits are tuned to the operating frequency of the transmitter. Transistor VT1 operates in key mode: the transmitter is on if this transistor is open to saturation.

The transmitter control unit is made on DD1 and DD2 microcircuits. On inverters DD1.5 and DD1.6, a generator is assembled, which is excited at a frequency of about 1 Hz. At a low level at the output of the DD1.5 element, the sound generator assembled on the inverters DD1.3 and DD1.4 is turned on. The pulses of this generator, following with a frequency of about 1 kHz, are used for frequency modulation of the master oscillator.

The generator signal on the elements DD1.5, DD1,6 (1 Hz) also controls the transistor VT1: the transmitter turns on are interspersed with pauses of the "clean" ether of approximately the same duration. By varying the frequencies of the generators, you can change the parameters of the alarm signal.

The sensor of the security system is a loop connected to connector X1.

A break in the loop will cause the low level at the input of the DD1.1 element to change to a high level and a low level will appear at the output of DD1.1. The high-level voltage will stop flowing through the VD2 diode, and conditions will be created to start the generators and the transmitter to enter the alarm signal transmission mode.

As important as the alarm is, it must be limited in time. The pulses received at the input From the counter DD2, after a while, will bring it to a state in which a high level occurs at the output 29. The transmitter will stop working after broadcasting 512 tone bursts. This will take about 9 minutes. By connecting the diode VD3 to other outputs of the counter DD2, you can change this time. To return the device to standby mode, press the SB1 button. The same button should be pressed when arming the device. The loop must be closed.

The transmitter is assembled on a printed circuit board made of double-sided foil fiberglass 1,5 mm thick (Fig. 2). The foil under the parts is used only as a common wire and screen: in places where the conductors pass, protective circles with a diameter of 1,5 ... 2 mm should be etched in it (not shown in Fig. 2). Connections of parts with a common wire are shown in black squares. The squares with a light dot in the center show the jumpers between the two sides of the board. Before installing the microcircuits, the conclusions 7 DD1 and 8 DD2 are bent to the side for soldering directly to the common wire foil.

(click to enlarge)

All resistors - MLT-0,125. Capacitors C1-C4, C10-C12, C14, C15 - KM-6 or K10-176; C5-C9 - KD-1; C13 - KD-2; C16 - oxide with a diameter of 6 and a height of 13 mm. Chokes L3, L4 - D0.1.

Coil L1 contains 60 turns of wire PEV-2 0,07, wound round to round, L2 - 13 turns (n1=7, n2=6) wire PEV-2 0,48, L5 - 11 turns of wire PEV-2 0,56 . Coils have M3x8 carbonyl trimmers. The design of the loop coil L2 and its mounting on the printed circuit board are shown in fig. 3. Coils L1 and L5 differ only in the absence of a tap. The coil frame L1 is glued to the board.

The quartz resonator can be simply soldered. But its actual resonant frequency often differs significantly from the one marked on the case. The selection of a resonator will be simplified if not the resonator itself is soldered into the board, but sockets for its pins (Fig. 4). These jacks (with an inner diameter of 1 mm) can be found in some connectors.

The printed circuit board is installed on the front panel - a plate cut from a sheet of high-impact polystyrene (holes 02,1 mm in the board are designed for its fastening). The transmitter body can also be glued from the same material; in the author's version, it had dimensions of 78x58x28 mm.

To establish the transmitter is transferred to the mode of continuous radiation without modulation. Short wire jumpers connect the collector of the transistor VT1 to a common wire (this ensures continuous power to the transmitter) and the left (according to the diagram in Fig. 1) resonator plate ZQ1 (this excludes the influence of the L1VD4C5 circuit).

A 50-ohm equivalent of the antenna is connected to the antenna output (two MLT-0,5 100 Ohm resistors connected in parallel), and a high-frequency (≥30 MHz) voltmeter and frequency meter are connected to it. A jumper simulating a loop is connected to connector X1.

By supplying power to the transmitter, by adjusting the coils L2 and L5, they achieve the highest voltage on the antenna equivalent. The power delivered to the load is calculated as Rizl (W) \u2d U50 / 2,5, where U (V) is the effective value of the high-frequency voltage shown by the voltmeter. The transmitter can be configured without a voltmeter, if you take an incandescent lamp 0,068 V XNUMX A as an antenna load: the best setting will correspond to the maximum brightness of its glow. By the brightness of this lamp, one can judge, very approximately, of course, about the radiation power.

If the frequency shown by the frequency meter differs from the required one by more than 0,5 kHz, the quartz resonator is replaced with another one.

Then the jumper is removed from the quartz resonator and by adjusting the L1 coil, the frequency is set 2 kHz higher than the operating one (if the loop is intact, then a high level voltage is set at the output of the DD1.4 element, which leads the frequency of the master oscillator up). If the connection of the frequency control circuit L1VD4C5 led to a breakdown in generation and it is not restored at any position of the trimmer L1, it is recommended to select a capacitor Sat. If the quartz resonator does not work on the third harmonic, but on the main one (which is rare, but it happens), the number of turns of the L1 coil must be reduced by 2-3 times and capacitor C5 should be selected.

The dependence of the main characteristics of the transmitter on the voltage of the power supply is shown in the table.

Here: Idej - the current consumed by the transmitter in standby mode (the loop is intact); Inepr - the same, in the mode of continuous radiation; Rizl - radiation power; ΔfB - deviation of the generation frequency upwards at a voltage across the varicap VD4 close to the supply voltage; ΔfH - downward deviation when the voltage across the varicap is close to zero. The table shows that a change in the voltage of the power source has little effect on the frequency of the emitted signal. At a voltage of 5 to 9 V, the signal remains in the band of the communication channel.

The final tuning of the transmitter is completed by adjusting the L1 coil by ear according to the best signal tone in the dynamic head of the receiver.

A socket for connecting an antenna is installed on the metal roof of the "shells". On fig. 5 shows the configuration of the hole for the antenna connector СР-50-73Ф, and in fig. 6 - cable connection. One end of the cable is attached directly to the transmitter board with a clamping bracket, the other is soldered to the connector.

The requirements for the source are simple: voltage - 6 ... 9 V, load current - not less than 1 Nepr. The electric capacitance of the source must ensure its sufficiently long operation. So, for example, a DL223A lithium battery (voltage - 6 V, capacity - 1400 Ah, dimensions - 19,5x39x36 mm) will allow you not to worry about power for several years. The battery can be made up of galvanic cells, but such a battery will last noticeably less.

If the transmitter is intended to be used in regions with a cold climate, it is necessary that the power supply remains operational even at low temperatures. Here, lithium galvanic batteries are also out of competition - their temperature range is from -55 to +85 ° C. Alkaline batteries are conditionally suitable (in winter) (-25 ... +55 ° С). RC and SC are completely unsuitable (0 ... +55 ° С). Less "frost-resistant" batteries. So, the temperature range of nickel-cadmium and nickel-metal hydride batteries is -20...+45 °C, and lithium - -20...+60 °C.

Any CB antenna can be installed on the "shell". The required "range" of the channel (usually several hundred meters) will be provided even by an antenna from a portable radio station. However, only a direct experiment can give confidence in this: in urban areas with a low emitter, signal interference at the receiving point is practically unpredictable.

In conclusion - about the receiver. In this capacity, single-channel CB radio stations, once produced by our industry, are attractive only for one thing: almost all of them have long been out of use. Although the "single-channel" radio receiver can work without alteration, it is better to modify it after all. First of all, a noise suppressor should be introduced into it (a device that turns on the UHF of the receiver only when a carrier frequency appears in the channel). The developers of the first domestic constantly hissing radio stations considered the noise suppressor to be an unnecessary luxury. After that, you can increase the signal power at the output of the UZCH and, if necessary, the amplification of the RF path. You can also experiment with AGC: increase or decrease its performance or turn it off altogether.

Of course, a radio station that is constantly on reception will also require a mains power supply. In this capacity, a power adapter is suitable, which has the desired output voltage and does not overheat during prolonged operation.

The antenna of the receiving "portable" may be her own. But it is better to take the antenna outside, fixing it, for example, on a balcony. Its metal armature, connected to the body of the connector, will serve as a kind of "counterweight". The regular antenna of the "portable" can be strengthened simply on the outside of the window frame. In this case, a freely hanging conductor about 1,5 m long is used as a counterweight (it is connected to the connector body).

The antenna from the "portable" requires moisture protection (first of all, its extension coil and antenna connector). The easiest way is to put a narrow plastic or rubber case on it.

Author: Yu.Vinogradov, Moscow

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