Auto guard with a three-tone siren. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Automobile. Electronic devices

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Almost all alarms in alarm mode emit an intermittent beep. The difference lies only in the frequency of repetition of beeps, which makes it difficult to distinguish the signal of your own car from the city noise. The problem can be solved by installing an additional emitter or supplementing the standard one with a special circuit.

Let us consider an auto-guard, which is simple in terms of circuit design, which, in the alarm mode, generates a sequence of sounds of three frequencies (750 Hz, 375 Hz and 187,5 Hz) with a repetition period of each 0,3 s. As a result, acoustic signals of a stepwise decreasing tone with a repetition period of 0,9 s are obtained.

The main technical characteristics of the device:

• Time to switch to armed mode, min.......1
• Alarm delay time, s.......5
• Alarm duration, s.......20
• Signal tone change period, s.......0,3
• Alarm tone, Hz.......750, 375 and 187,5
• Alarm dimensions, mm.......70x70

The circuit diagram of the autoguard is shown in Fig.1.

Fig.1 (click to enlarge)

The device contains a single vibrator on the elements DD1.3 and DD1.4, a master generator (3000 Hz) on the elements DD2.I and DD2.2, a clock generator (3 Hz) on the elements DD2.3 and DD2.4, two counters on the DD3 chip and a switch on DD4 and DD5 chips. The watchman also includes a powerful pulse key on transistors VT1, VT2 and a sound emitter VA, converted from a car signaling device.

When the autowatch is turned on, capacitor C5 begins to charge through resistor R4. At the same time, at the inputs of the elements DD2.1 and DD2.3 there is a zero level, which blocks the master and clock generators. After charging the capacitor C4 (after about 1 min), a positive potential appears on the cathodes of the diodes VD5 and VD6 and they close. The device goes into armed mode.

When the contacts of the door sensors SB1-SBn are closed through the elements DD1.1, DD1.2 and the diode VD2, the zero potential is fed to the input of the single vibrator on the elements DD1.3 and DD1.4. As a result, a log appears at pin 6 of the DD1.3 element of the one-shot. "1", which, through the delay circuit R4, C3, enters the cathodes of the diodes VD3 and VD4. The diodes are closed. In this case, the low-level voltage at pins 1 and 13 of the elements DD2.1 and DD2.3 allows the operation of the master (DD2.1 and DD2.2) and clock generators (DD2.3 and DD2.4). Circuit R4, C3 generates a delay of 5 seconds, which is given to the car owner to turn off the alarm with a hidden toggle switch. Otherwise, the circuit goes into alarm mode. The sounding time of the alarm signal depends on the ratings of the circuit elements R3, C2. After 20 seconds, the circuit enters the protection mode.

In alarm mode, pulses with a frequency of 3 kHz from the output of the master oscillator are fed to the counting input C (pin 2) of the counter DD3!1, which is used as a frequency divider. The division ratio on its output 4 is 4, on output 5 - S, on output 6 - 16. Thus, at outputs 2, 4, 8 of the counter there are pulses with frequencies of 750 Hz, 375 Hz and 187.5 Hz, respectively.

The valves on the elements DD4.1 DD4.3 alternately pass pulses to the output of the device, with the frequencies indicated above. The switching sequence sets them clock counter DD3.2, counting 'input C (output 10) which receives a signal with a frequency of 3 Hz from the clock generator. In the case when the outputs 11 and 12 of this counter are log. "0", all three gates are closed. After the first pulse arrives at the input C of the counter DD3.2, a log appears at pin 11. "1", which opens the element DD4.1 and pulses with a frequency of 750 Hz pass through it to the input of the element DD5.1 ​​and then go to the input of the pulse switch on transistors VT1 and VT2. The signaling device BA emits a tone signal with a frequency of 750 Hz.

Upon arrival of the second pulse to the counter DD3.2, a log appears at pin 12. "1", which opens element DD4.2, a signal with a frequency of 375 Hz is sent to the signaling device BA. Then, after 0,3 s, a log is set at both outputs 11 and 12 of DD3.2. "1", and element DD5.2 opens valve DD4.3 (elements DD4.1 and DD4.2 at atom are blocked by zero potential through diodes VD9 and VD10), and a signal with a frequency of 187,5 Hz is sent to the signaling device VA. After the next 0,3 s, log levels are set at both counter outputs. "0" and the weight of the three gates are closed for a time of 0,3 s, during which the device does not emit a sound signal. Thus, in the alarm mode, the device generates an intermittent signal of stepwise changing tone.

As a signaling device VA, a regular car signaling device from a Zhiguli car is used, in which the interrupter is removed. It is very easy to do this. To turn off the breaker, just unscrew the adjusting screw on the signaling device. You can check this by briefly connecting the device to the battery - a short click and more sounds will be heard in it.

To control the VA signaling device, a pulse key is used on a VT2 transistor of the KT827 type, which can switch current up to 20 A. During operation, the VT2 transistor heats up, so it must be installed on a radiator.

The three-tone watchman is mounted on a printed circuit board made of double-sided foil fiberglass with a size of 70x70 mm (Fig. 2).

Ris.2

In the circuit, instead of microcircuits of the K561 series, you can use similar microcircuits of the K564 series, but this will require a change in the design of the printed circuit board. The K561IE10 counter can be replaced by any two other binary counters of this series, for example K561IE11. Capacitors C2, C3 and C4 are preferably used with a low leakage current, for example, type K53-4 or K50-35. The location of the autoguard elements on the printed circuit board is shown in Fig.3.

Ris.3

Transistor VT2 is mounted separately on the cooling radiator and connected to the watchdog board and the VA signaling device with a stranded wire.

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