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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Guard blocker of the ignition system. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Automobile. Ignition Technical means that make it difficult for unauthorized use of a car still remain its necessary equipment. Despite the wide range of proposed proprietary electronic security systems, the technical literature continues to publish new designs with various security functions. This allows car owners to choose for each practical case an anti-theft device with the required set of service characteristics and the most acceptable price/quality ratio. The blocker belongs to the group of so-called VRS devices (Vehicle Recovery System - system for returning a stolen car) (Kryuchkov V. Electronics against the robber. - Behind the wheel, 1996, No. 7, p. 40). They begin to work immediately after the car is stolen by an attacker. Although many such devices are known, they are all, as a rule, foreign-made, and their price is not affordable for everyone. The blocker version described below uses components produced in the CIS countries. This determines the low cost of the product as a whole. In addition, the range of functions it performs is very wide, and the use of the digital principle of forming time intervals, protection from interference and overloads ensure high reliability. The blocker can be installed on any car model equipped with an engine with a spark ignition system and a rated on-board voltage of 12 V. The principle of operation of the device is that after turning on the ignition and starting the engine, it gives the driver some time to press the secret button. button (or close the reed switch), thereby switching the protection system to its original state. If this is not done, the device will first sound a local warning signal, and then turn off the ignition and turn on the emergency sound (and light - turn indicator lamps) alarm. If the driver is attacked, when he is forcibly pushed out of the car during a short stop with the engine running and the door open, the device is also triggered. In the case when the driver needs to open the door without turning off the engine, he must then “reset” the lock by pressing the secret button, otherwise after 16 s a warning signal will sound, and after another 16 s - an alarm signal with simultaneous shutdown of the engine. The electrical circuit diagram of the blocker connected to the vehicle's on-board network is shown in Fig. 1, and the work cyclogram is in Fig. 2. The device does not have a power switch and is constantly in standby mode. In this case, triggers DD1.1 and DD1.2 are in the zero state. At a low level from the direct output of trigger DD1.1, the clock generator on elements DD2.1 and DD2.2 is inhibited, and the counter DD3 is reset to zero. Generators assembled on elements DD4.1, DD4.2 and DD4.3, DD4.4 are also inhibited. In standby mode, the blocker consumes a current of about 0,5 mA.
When the ignition is turned on, supply voltage is supplied to pin 1 of the blocker, the base current of transistor VT10 flows through resistor R3 and it opens - ignition relay K1 is activated. At the same time, a short pulse arrives at the input S of trigger DD1.1 through the discharged capacitor C1 and resistor R7, which sets the trigger to state 1. A high level from the direct output of the trigger starts the clock generator DD2.1, DD2.2. The ratings of the R18C9 circuit are selected in such a way that the generator operates at a frequency of about 1 Hz. The output of the clock generator through resistors R19, R22 and R23 is connected, respectively, to the clock input of the binary five-bit counter DD3, to the control input of the generator DD4.1, DD4.2 (via intermediate resistor R24) and to the base of transistor VT7. Counter DD3, which was in the zero state, begins counting clock generator pulses (time counting). For 16 s, a low voltage level operates at outputs 16 and 32 of the counter, diodes VD8 and VD9 are open and the clock generator pulses do not reach the input of the generator DD4.1, DD4.2 and transistor VT7. If, before the expiration of this time, the on-board voltage is briefly applied to pin 3 of the device by closing the contacts of the SB1 button (reed switch or any other method), the trigger DD1.1 will switch to its original state and prohibit the operation of the clock generator DD2.1, DD2.2. The differentiating circuit C4R12 will generate a pulse that will reset the counter DD3 and start the one-shot device assembled on the trigger DD1.2. When starting and switching back the single-vibrator, two high-level pulses with a duration of 5...6 s will be generated at the junction point of diodes VD0,1 and VD0,2 with an interval between them of 0,5...0,7 s. Having arrived at the triggering input of the generator DD4.3, DD4.4 (to pin 1 of element DD4.3), they will cause the appearance of two packs of rectangular pulses with a frequency of about 2500 Hz, which will pass through resistor R32 to the input of a push-pull power amplifier on transistors VT9 and VT10 . The amplifier load - piezoceramic sound emitter HA1 - will play two short beeps confirming the device has returned to standby mode. The device can remain in this state for as long as desired, keeping the ignition relay turned on. If by the time a high level appears in the fourth digit of the counter DD3 (at output 16), a zeroing pulse has not been received at pin 3 of the blocker, the VD8 diode will close and allow the operation of the generator DD4.1, DD4.2, which will begin to generate a pulse sequence with a frequency of about 10 Hz. The combined operation of the clock generator and generators DD4.1, DD4.2 and DD4.3, DD4.4 produces a series of 16 sound signals reminding the driver of the need to stop the timing by applying a zero pulse to pin 3 of the device. In the case when there is no zeroing pulse, after 32 s a high level appears in the fifth digit of counter DD3 (at output 32), the base current of transistor VT21 begins to flow through resistor R2, it opens and closes transistor VT3, which turns off the ignition relay K1 and stopping the engine. Diode VD8 opens again and stops generators DD4.1, DD4.2 and DD4.3, DD4.4 - the warning sound stops. Diode VD9 closes, and current pulses from the base of transistor VT23 begin to flow through resistor R7. Transistors VT7 and VT8 begin to open and close at the frequency of the clock generator and periodically turn on relays K3 and K4 for the vehicle's sound and light alarms. In addition, the base current of transistor VT28 begins to flow through resistor R5. Transistors VT5 and VT6 open, and relay K2 of the siren is activated, which can be used as an alternative or addition to the existing sound signal. There is a high level at the inputs of element DD2.3, and a low level at the output, so diode VD7 is open and prohibits the arrival of clock generator pulses at the input of counter DD3. Until the ignition is turned off (until the voltage is removed from terminal 1 of the device), the state of the DD3 counter will not change, the winding of the ignition relay K1 will be de-energized, and the sound and light alarms will be turned on. This state corresponds to the time interval t on the cyclogram (Fig. 2). Its duration depends on how soon the ignition key is returned to the “Ignition off” position. Immediately after this, capacitor C8 is quickly discharged through diode VD4 and resistor R5, a low level appears at the upper input of element DD2.3 in the circuit, and a high level appears at the output. Diode VD7 closes, counter DD3 will continue to operate for another 32 s until it overflows and all bits are reset to zero. A transition to a low level at output 32 will cause a negative voltage drop at the input of the inverter DD2.4. From its output, a short high-level pulse through diode VD13 is supplied to the R input of trigger DD1.1 and returns the blocker to standby mode, similar to a zeroing pulse at pin 3. If you restart the engine, the operating cycle will repeat. Capacitor C8, resistor R11 and diode VD4 make up the circuit for suppressing the bounce pulses of the ignition switch contacts. In its absence, if turning off the ignition switch coincides in time with a high level at the output of the clock generator, a packet of “bouncing” pulses from the contact group of the ignition switch will be transmitted through element DD2.3 to the input of the counter DD3 and can immediately cause it to overflow and return the device to standby mode. This will make it possible for the engine to restart and thereby reduce the efficiency of the device. Capacitor C8 also prevents the passage of pulses to the clock input of the counter DD3, which can be created by periodically turning the ignition switch on and off. Thus, the established time interval (32 s) for blocking the ignition, as well as the operation of the sound and light alarms, is the minimum possible. As already noted, the blocker comes into operation not only at the moment the car is stolen, but also when it is taken over by force. In this case, when the door is opened, the contacts of the door switch SF1 close and terminal 2 of the device is connected to the car body. Transistor VT1 opens and switches trigger DD1.1 to the single state. The countdown begins in the same way as when the ignition is turned on. The inverter, assembled on transistor VT4, prohibits the operation of generators DD4.1, DD4.2 and DD4.3, DD4.4 in the third quarter of the cycle (Fig. 2), when the output 16 of the DD3 counter is high, but there is a warning sound signal in this the situation is no longer needed. Capacitor C3 allows you to set the DD1.1 trigger to its initial (zero) state when you turn on the device for the first time. Capacitor C2 reduces the effect of noise at the input S of trigger DD1.1. Diodes VD3 and VD12 protect the inputs of the corresponding elements, and diodes VD10, VD14 and VD16 protect transistors VT3, VT6 and VT8 from breakdown of the self-induction EMF that occurs in the relay windings when the transistors are quickly closed. Diodes VD15, VD18 and VD19, as well as VD20, VD21 are used to isolate the device from the vehicle's electrical circuits. To power the main components of the blocker, a voltage stabilizer is provided on the zener diode VD17 and transistor VT11. Capacitor C13 suppresses interference that occurs during the operation of vehicle electrical equipment. The blocker is mounted on a printed circuit board made of single-sided foil fiberglass 1 mm thick. The board drawing is shown in Fig. 3. The device uses resistors MLT-0,25 or MLT-0,125, capacitors are from the KM series, oxide capacitors are K50-35.
Most of the resistors on the board are installed "upright" (perpendicular to the board). Oxide capacitors C8 and C13 are placed above the housings of microcircuits DD2 and DD4, respectively. The board has foil pads for mounting capacitors C2, C10 and C11, both conventional and those designed for the surface method - on the printing side (C11 is made up of two 0,033 μF each). Transistors KT315G can be replaced with KT315B, KT315E, and KT361G with KT361B, KT361E. Instead of KT815G, transistors KT815B, KT815V or KT817 with any letter index are suitable. KD102A diodes can be replaced with KD521A, KD522A, KD510A or any others with a maximum forward current of 100 mA. Zener diode VD17 - any low-power voltage 9...10 V; in Fig. Figure 3 shows its polarity in a zener diode connection. The piezoceramic sound emitter HA1 is mounted on the board on its own wire stands, which must first be unsoldered and soldered again perpendicular to the plane of the emitter body. The racks are soldered into the board into the holes indicated in Fig. 3 letters A, and this ensures not only fastening, but also electrical contact of the housing with the common wire. Two flexible leads are soldered into two holes on the board, marked with the letter B. The board with the parts is installed in a plastic box of suitable dimensions, in the wall of which several small holes are drilled opposite the piezo-sound emitter. The box is placed inside the car in a hard-to-reach place (for example, behind the dashboard). The installation location of the SB1 secret button should be carefully considered. It should be accessible, but, if possible, inconspicuous. The device is connected to the vehicle's electrical system with flexible wires (for example, PGVA) with a cross section of 0,5...1 mm2. With serviceable parts and correct installation, the device begins to work immediately. Sometimes it is necessary to select resistors R18, R26 and R31. By selecting resistor R18, the desired time intervals in the cyclogram are set. The frequency of generators DD26, DD31 and DD4.1, DD4.2, respectively, depends on the resistance of resistors R4.3 and R4.4. If necessary, the selection can be made not by the frequency of the generators, but by the volume of the warning signal. After adjusting and checking the blocker in operation, the board should be coated with a thin layer of epoxy compound - this will increase the rigidity of the installation and the moisture resistance of the device as a whole. "Surface" capacitors on the board require mandatory protection with a compound. Author: S. Ryzhkov, Bishkek, Kyrgyzstan
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