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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Electronic watchdog for a motorcycle. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Security devices and alarms There are many descriptions of burglar alarm devices for cars in amateur radio literature. However, most of these devices cannot be used to guard another popular vehicle - a motorcycle. The author of the article published below developed his design specifically for the "two-wheeled friend" and believes that it fully meets the goal. During the collection of forest gifts of nature, motorcycles standing alone along roads and clearings become easy prey for intruders. True, motorcycles are rarely stolen, but they are dismantled, fuel is stolen while the owners are picking berries or mushrooms, quite often. The proposed watchman reacts even to a slight blow to the body of the motorcycle and immediately gives an alarm. Moreover, the signal is musical and, of course, differs from traditional alarm signals. The owner easily recognizes him among others. When developing a security device, it was necessary to immediately abandon the use of a sound signal installed on a motorcycle, since it consumes too much current from the battery. The described watchman consumes no more than 1,5 mA in standby mode, and up to 400 mA in alarm mode. The device uses a sensor similar to that described in [1]. It is based on the ZP-22 piezo emitter, which is installed on the board without modification. The sensor can be placed anywhere on the motorcycle; this does not significantly affect the efficiency of the watchman. The electrical circuit diagram of the security device is shown in fig. 1. When hitting the body of the motorcycle in the BQ1 sensor, an alternating current signal occurs, which is fed to the input of the comparator assembled on the op-amp DA1. The threshold for the comparator is set by a trimmer resistor R2. The upper position of the slider of the resistor R2 according to the diagram corresponds to the minimum sensitivity of the device.
If the amplitude of the negative half-waves of the sensor signal is less than the voltage across the resistor R2, the transistor VT1, operating in the switching mode, remains closed, and the output voltage on its collector is low. As soon as the amplitude of the half-waves exceeds the voltage across the resistor R2, the output voltage of the transistor VT1 will be a sequence of rectangular pulses. Diode VD1 increases the dead zone of the transistor VT1. Operational amplifier DA1 operates in maximum gain mode. The current drawn by the op-amp depends on the current flowing through pin 8; resistor R5 normalizes this current. If it is within 1,5 ... 15 μA, then the current consumed by the op-amp DA1 is 36 ... 170 μA. The resistance of the resistor R5 (in megaohms) is calculated according to the formula [2]: R5 = (Upit-0,7V)/I8, where Upit is the supply voltage of the OS, V; I8 - current through pin 8, µA. Rectangular pulses from the collector of the transistor VT1 are fed to the input S of the trigger DD1.1, which leads to switching it to a single state. The trigger direct output is set high. Subsequent pulses coming from the collector VT1 to the input S of the flip-flop no longer change its state. The high-level voltage from the output of the trigger DD1.1 through the resistor R9 begins to charge the capacitor C1 relatively slowly. Its charging time is about 40 s. As soon as the voltage on the capacitor C1, and hence at the input R of the trigger, reaches the trigger switching threshold to the zero state, the trigger will switch and the direct output will go low if the transistor VT1 has closed by this moment and the input S of the trigger has stopped receiving pulses. Op-amp DA1 and trigger DD1.1 are powered by a parametric voltage regulator VD2R10. The high-level voltage at the direct output of the trigger DD1.1 opens the transistor VT2, and the relay K1 is activated. Through the closed contacts K1.1, K1.2, power is supplied to the signaling device assembled on the DD2 musical synthesizer. In addition to a musical synthesizer, it includes a DA2 audio signal amplifier and a BA1 dynamic head. Music synthesizer DD2 is powered by a separate parametric stabilizer VD4R12. The synthesizer is connected so that only one melody sounds. If it is necessary to change the melody, then the scheme of its inclusion must be changed, as shown in [3]. The AF signal amplifier DA2 is powered directly from the motorcycle battery. Resistor R13 prevents self-excitation of the amplifier. The OS chain is formed by elements C5, R14, R15. Resistor R15 must be selected during adjustment in such a way as to achieve the maximum gain [4]. Dynamic head BA1 is connected to the amplifier DA2 through a decoupling capacitor C6. Free pins 3-6, 9, 11 of the DD1 chip are connected to a common wire. All parts of the device, except for the SA1 switch and the BA1 dynamic head, are mounted on a printed circuit board made of foil fiberglass 1 mm thick. The drawing of the board is shown in fig. 2.
Switch SA1 should be installed in a place known only to the owner of the machine. The dynamic head must be protected from deliberate damage. It is desirable to impregnate the diffuser with a waterproof varnish. The board also needs to be protected from splashes and dust with a durable box, and the mounting should be coated with epoxy varnish. The vibration sensor can be made on the basis of the ZP-1 sound emitter and others. The K140UD1208M chip can be replaced with K140UD12, and the K176TM2 trigger with K561TM2. Synthesizer UMS8 - any of this group; they differ only in the melodies recorded in them. The ZQ1 quartz resonator is suitable for any clock at the specified frequency. Instead of the K174UN14 amplifier, the TDA2003 is suitable. Transistors VT1, VT2 can be any of the indicated series. Diodes VD1, VD3 - also any of the series KD521, KD522. We will replace the KS512A zener diode with KS212Zh, and KS139A - with KS133A or with a KS119A stabistor, but with a change in the switching polarity. Relay K1 - RES60, passport RS4.569.435-02. The dynamic head 3GDV-1 can be replaced with 2GD36, 4GD56, 6GDV-2. Pushbutton switch SA1 - P2K. Accurately assembled from serviceable parts, the device usually starts working immediately. Resistor R2 regulates its sensitivity after placement on the motorcycle. It is not recommended to set the sensitivity too high, otherwise the alarm will react to the vibration of the soil from a passing vehicle, and even to slight crackles of a motorcycle cooling down after stopping. The sensitivity also depends on the location of the vibration sensor - when it is attached to the frame or other metal structural elements, the sensitivity may be excessive. To exclude acoustic communication between the dynamic head BA1 and the vibration sensor BQ1, as a result of which the alarm signal will be repeated continuously without external influences on the sensor, it is necessary to experimentally select the location of the head, the rigidity of its fastening and the sensitivity of the sensor. The watchman is powered by a motorcycle battery. If the vehicle is running without a battery, it must be installed. In standby mode, the device is switched on by closing the SA1 contacts. If you then try to manipulate the control levers, remove the motorcycle from the footrest or move it, the watchman will immediately give an alarm signal. It will sound for about 40 seconds, during which time the melody will have time to sound completely. Then, provided that external influences have ceased, the burglar alarm will go into standby mode. As you know, there are not so many places on a motorcycle suitable for installing a dynamic head, so there is no reason to expect that it will be possible to ensure the absence of a parasitic acoustic-mechanical connection between it and the sensor (with its acceptable sensitivity). Nevertheless, this parasitic connection can be eliminated by a simple modification of the watchman. First, you need to "transfer" one of the two contact groups of the K1 relay (see diagram) to the break in the positive wire at point B, and use a pair of closed relay contacts (with terminals 11, 12 or 21, 22). The trigger DD1.1 should be powered from the positive output of the Zener diode VD2. Secondly, the capacitor C2, having increased its capacitance by 2 ... 5 times, must be soldered to the left of point B according to the scheme, and a ceramic one with a capacity of 0,1 ... 0,22 μF should be installed in its original place. After this alteration, in standby mode, the op-amp and the guard transistor VT1 will work as indicated in the article, but as soon as relay K1 is activated and an alarm sounds, the op-amp and transistor VT1 will be de-energized. After some time, the relay will return to its original state, but the sensitivity of the watchman will be restored only after 0,1 ... 0,3 s after the oxide capacitor C2 is charged. Literature
Addition Since it is extremely difficult to eliminate motorcycle crackles, false alarms of the watchman have to be dealt with. The diagram of the signaling device, free from the indicated drawback, is shown in the figure. Vibration sensor BQ1 is left the same, but the scheme of its connection to the comparator on the op-amp DA1 is somewhat changed.
Counter DD1.1 counts the pulses coming from the comparator. The generator on the elements DD2.1, DD2.2 and the counter DD1.2 form a node that generates pulses to reset the counter DD1.1. On the elements DD2.3, DD2.4, an audio frequency generator is assembled, its output pulses are amplified by current by the transistor VT1, loaded with a dynamic head HA1. The device is put into standby mode by a covertly installed toggle switch SA1. At this moment, the pulse from the C2R5 circuit resets the counters DD1.1 and DD1.2 at the input R. The generator DD2.1, DD2.2 starts to generate rectangular pulses with a frequency of about 2 Hz, which the counter DD1.2 takes into account. After about 4 s, output 8 of this counter will briefly go high, which will reset the counters again. In the future, every 4 s, zeroing pulses will be sent to the input R of the counters. Voltage fluctuations from the BQ1 sensor, resulting from the vibration of the motorcycle frame, are fed to the non-inverting input of the op-amp DA1, which is turned on by the comparator. A voltage is applied to the inverting input of the op-amp from a divider - a tuned resistor R3, which sets the comparator switching threshold or, in other words, sensitivity. Rectangular pulses from the output of the comparator are counted by the counter DD1.1 at the input CN. If in 4 seconds the counter has time to count eight pulses, then a high level will appear at its output 8, which will allow the operation of the sound generator on the elements DD2.3, DD2.4. The duration of the alarm signal depends on how soon the counter registers eight pulses, or, in other words, how intense the vibration of the machine body is. Thus, the insensitivity of the watchman to single clicks is ensured. In case of accidental external influences on the motorcycle, it will give short non-periodic signals, and only when trying to steal or dismantle parts, the alarm will sound almost continuously. Diode VD2 protects the device from accidental reversal of the supply voltage polarity. The time of accumulation of impulses of external influence and the duration of the sounding of the alarm signal can be increased if the capacitor C1 is replaced with another, larger capacitance. So, with a capacitance of 1 uF, the duration will almost double. For reliable operation of the watchman, it is necessary to carefully set the required sensitivity of the comparator with the tuning resistor R3. Before the first start, the slider of this resistor is set to the middle position. The watchman is turned on and, by monitoring the signal at the output of the comparator with an oscilloscope and tapping on the body of the motorcycle, slowly move the slider of the resistor R3 down the circuit, achieving the operation of the watchman. Recommendations for the placement of the sensor, device design, mounting of the dynamic head, taking into account the possibilities of acoustic communication between the head and the sensor, are set out in the above article. Since the device does not require high temperature stability of RC circuits, almost any parts can be used in it. The K140UD608 chip can be replaced with K140UD6, K140UD7. Instead of K561LE5, K561LA7 is suitable, in this case, you can exclude the VD1 diode, connect one of the inputs of the DD2.3 element to output 8 of the DD1.1 counter, and the other to the connection point of the elements R8 and C3. We will replace the ZP-22 sound emitter with ZP-5. Instead of the KT972B transistor, any of the KT829 series will do. Diodes KD522B can be replaced by any silicon ones (for example, from the KD521 series). The watchman consumes about 6 mA in standby mode, and about 300 mA in alarm mode. It can be powered from a motorcycle battery, or from any other source that provides a current of at least 300 mA for at least an hour. To ensure the installation of optimal sensitivity and ensure its stability, it is better to choose the resistance of the tuning resistor R3 equal to 10 kOhm and connect it in series with a constant resistor with a resistance of 43 kOhm to the circuit of the upper and lower according to its terminal diagram. Author: M.Churuksaev
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