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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Motorcycle security alarm. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Security devices and alarms It seems to me that one of the most successful designs of a motor guard should be recognized as the device of M. Churuksaev [1]. It became a kind of model for subsequent developments by other authors (for example, V. Bannikov [2]). Although both [1] and [2] use a dynamic direct-radiation head to reproduce the alarm, in many cases it is more convenient to use the sound signal available on the machine. Given the limited capabilities of a motorcycle battery, in order to increase the efficiency of the watchman, but not to the detriment of the reliability of the guard, it is necessary to exclude false alarms. In my opinion, insufficient attention has been paid to this issue in these works. It is known that it is not possible to clearly separate the sensor signals caused by the human factor (not to mention whether malicious intent is present) from others arising from the impact of passing vehicles, wind, etc., it is not possible. Therefore, it is desirable to exclude the watchdog operation from short bursts of sensor pulses (at least less than 1 s long), and even more so from single pulses. In other words, connecting the output of the signal amplifier of the vibration sensor directly to the trigger input of the security device should be recognized as a disadvantage. In view of the above, the construction [1] has been revised. The music synthesizer and audio frequency amplifier have been replaced by a conventional horn relay. Measures have been taken to reduce the likelihood of false positives. Parasitic acoustic-mechanical feedback between the sensor and the sound signal is eliminated by a non-relay method - for the duration of the alarm, the electronic unit blocks the passage of vibration sensor pulses to the guard input, after which the blocking is removed with some delay. Contact sensors are provided that increase the overall reliability of protection The circuit diagram of the watchman is shown in fig. one.
The electronic unit is assembled on just one microcircuit, but nevertheless contains all the functional components necessary for such devices: trigger, timer, generator. The role of the trigger and timer is played by a single vibrator made on Schmitt triggers DD1.2 and DD1.3. The C3R4 circuit determines the duration of the high-level pulse at the output of the single vibrator, which corresponds to the duration of the sounding of the alarm signal (at the ratings indicated in the diagram, approximately 23 ... 25 s). On the Schmitt trigger DD1.4 and the frequency-setting circuit C6R5, an oscillator was assembled at a frequency of about 0,7 Hz. With this frequency, the signal relay K1 is periodically turned on - the load of the current amplifier on the transistor VT1. The Schmitt trigger DD1.1 provides the watchman's insensitivity to the sensor pulses for the duration of the alarm and also after it ends for the time determined by the R3C2 circuit. This eliminates the re-activation of the watchdog under the influence of damped oscillations of the motorcycle frame and the sensor piezoelectric element itself, caused by the acousto-mechanical effect of the sound signal. The R1R2C1 circuit matches the vibration sensor with the watchman's electronic assembly. This sensor, developed by Yu. Vinogradov [3], except for M. Churuksaev and V. Bannikov, was also used without change by V. Pryamushko [4] in his car guard. The sensor is good because it not only works in almost any position, but is also easy to manufacture and cheap. Nevertheless, I had to conduct a series of experiments with a mechanical-to-electrical vibration converter (with a BQ1 piezoelectric element and its fasteners) in order to increase sensitivity and reliability when working as a watchman on a motor vehicle. To combat false positives, Yu. Vinogradov suggested using an analyzer on a pulse counter. With the converter I propose, the simplest integrating circuit R2C1 with a shunt resistor R1 works better. It takes into account not only the frequency of the captured pulses, but also their duration and amplitude. Since the capacitor C1 is charged through the resistor R2, and is discharged through the total resistance of the resistors R1 and R2, the time of its charging and discharging is not the same. It is easy to see that by changing the ratio of the values of resistors R1 and R2, it is possible to eliminate the influence on the operation of the motor guard not only of single, in no way mutually related pulses, but also of bursts (and even continuous oscillations). This is a very useful feature, for example, to protect against fluctuations caused by heavy rain (with appropriate detector sensitivity). As noted, with a significant vibration intensity, rectangular oscillations with a more or less certain frequency, a duty cycle close to two, and an amplitude equal to the supply voltage are established at the sensor output. The R1R2C1 circuit determines the alarm turn-on delay, which is desirable to choose at least 1 s. The R1R2C1 circuit is suitable for use with other vibration sensors. It is only necessary to select the ratings of its parts accordingly. The use of Schmitt triggers in the watchdog improves the clarity of switching in conditions of a relatively slowly changing input voltage. Relay K2, controlled by contact sensors SF1, SF2, works in a motorcycle additional protection device. It can be useful when the vibration sensor is out of order (or its use is difficult, for example, by weather conditions) or the electronic assembly, and also if the motorcycle is out of sight (in forest, in a garage near the house) The fact is that quite soon the ear already clearly fixes against the background of noise a single activation of the alarm (you can even count the number of activations of the signal - 17-18 with the ratings of the R4C3 circuit indicated on the diagram). Such a signal clearly indicates the operation of the vibration sensor, but does not allow one to unambiguously judge its cause. If the sounded signal is suddenly interrupted unexpectedly, this should cause legitimate concern. It may also happen that your motorcycle hit another vehicle. Then the contact sensors will not turn off the signal until you intervene. As contact sensors (there may be several of them connected in parallel), both push-button switches and closed reed switches are suitable. The diagram shows both options. In the security mode, the closed contacts of the switch SF1 and the reed switch SF2 must be open, while relay K2 is de-energized and its contacts are also open. The push button SF1 can, for example, be installed under the seat (where the tools are usually located) so that the saddle, fixed in its place by a latch, presses the button and opens the contacts. When you try to remove it, the contacts will close. The reed switch can be installed inside the frame tube, in which the axle of the front wheel fork rotates on bearings (this option, however, requires dismantling the steering assembly with dismantling the upper bearing). The reed switch is fixed through a non-magnetic gasket to the inner wall of the frame tube, and a magnet is installed on the fork shaft opposite the reed switch through the same gasket in such a way that the reed switch is activated (opened) when the steering wheel is turned from one of the extreme positions by about a quarter of the full angle of its rotation. In this case, when you try to steal a motorcycle, remove a wheel, etc., the reed switch will close. In order to make it easier for the owner to set the steering wheel to the required position, the HL1 LED is used. After the device is triggered, the alarm sounds regardless of the further state of the reed switch, and the LED is de-energized in armed mode. The device is not critical to the choice of parts. The temperature conditions of the motorcycle operation allow the use of oxide capacitors in timing circuits (miniature imported ELNAs were used). Relay K1 is a small-sized imported HG4123 / 012-1C, which made it possible to mount it on the board. Widely used automotive relays will do, but you will have to install the relay next to the signal. Relay K2 - any small-sized one with the corresponding response voltage (for example, RES49, passport RS4.569.421-02). The SF1 button must withstand heavy mechanical loads - car interior lighting switches mounted on the doors, or a switch from the KR series (push-button breaker), are suitable. The reed switch is used with changeover contacts (leave the unused output free). The board with the details of the electronic assembly is placed in a solid metal box-screen. The sensor consists of a vibration transducer, the basis of which is a piezoelectric element from the ZP-18 sound emitter, and an amplifier-shaper assembled on the op-amp DA1 and the transistor VT1 (see the diagram in Fig. 2, borrowed from [3]).
The piezoelectric element on a brass plate is removed from the sound emitter housing and two racks of steel elastic wire with a diameter of 0,5 ... 0,7 mm are soldered to it, as shown in Fig. 3. One stand is soldered to the edge of the plate, and the other to the conductive coating of the piezoelectric element also near its edge. The soldering posts should be parallel to one another.
In order not to damage the piezoelectric element during soldering, it is desirable to use the most fusible solder and, accordingly, reduce the heating temperature of the soldering rod. You should not strive for the minimum area of the soldered contact on the piezoelectric element - during operation, the soldering may peel off. The optimal area is about 3x4 mm. The distance between the racks is 9,5. 10 mm. At the far end of the resulting console from the racks, an additional weight is soldered from the solder to the edge of the brass plate on the side opposite to the piezoelectric element. Adding or subtracting the weight of the weight, it is easy to adjust the sensitivity of the transducer. The free ends of the transducer legs are tinned and soldered into the board during the final assembly of the sensor. The board is made of foil fiberglass with a thickness of 1,5 mm. The drawing of the board is shown in fig. 4. The board is placed in a casing-screen, soldered from tin, which is attached to the motorcycle body with a self-tapping screw. The converter BQ1 must not touch the walls of the casing during operation.
Sensor dimensions - 25x25x18 mm. It is connected to the electronic node with three conductors in reliable insulation. Capacitor C1 in the sensor -K53-19 - blocking in the power circuit. The board is designed to install a KT361G transistor, but the best results were obtained with an imported 2SA881R transistor with a similar pinout. Trimmer resistor R2 - SPZ-19a. When setting up a watchman, the desired time delays are specified by selecting the values of RC circuits. It is more convenient to adjust the parameters of the R1R2C1 chain directly on the motorcycle. To do this, the resistor R2 is replaced with a trimmer, instead of the resistor R1, another one is soldered with a resistance of 1 ... 2 kOhm (to limit the collector current of the sensor transistor), as shown in Fig. 5.
The resistor slider is set to the leftmost position according to the scheme - minimum sensitivity. Then they try to remove any easily removable part from the motorcycle (at least the gas tank cap). The watchdog should not trip. By moving the resistor slider to the right in stages according to the scheme, they ensure that the removal of the part causes a clear operation of the watchman. Manipulations when removing a part should be as similar as possible. After each impact on the sensor, it is necessary to maintain a pause to discharge the capacitor C1. Having found the required position of the resistor R2 slider, measure the resistance of the resulting divider arms and replace them with constant resistors. Before setting the watchman to standby mode, set the motorcycle steering wheel to the position at which the HL1 LED goes out, and turn on the power with the SA1 toggle switch. In conclusion, it should be noted that the reliability of protection largely depends on the secrecy and inaccessibility (within a reasonable time interval) of the elements that ensure it. Therefore, it is desirable to provide a strong metal well-locked box for the battery, protect the sound signal with a casing, and lay the corresponding wiring in the motorcycle frame. The practical implementation of these measures may vary depending on the type of vehicle. Literature
Author: A.Martemyanov, Seversk, Tomsk region
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