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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Security device for the garden plot. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Safety and security Many owners of garden plots every year have the problem of protecting their crops from the encroachments of robbers. Sometimes the presence of a guard dog does not help, for example, with a large perimeter of the site. Significant assistance in this case can be provided by an electronic watchdog device, which uses "stretch marks" made of thin copper wire with a diameter of 0,1 ... 0,2 mm and reed sensors (on greenhouse doors and gates) as penetration sensors. Unlike those described earlier [1] - [3], the proposed device has four independent channels for monitoring three security loops and the presence of a mains voltage of 220 V. The need for its control is caused by frequent cases of theft of lighting network equipment in rural areas and gardening communities . A break in each channel is fixed regardless of the current state of the loop, i.e. if the greenhouse door was opened in your absence, you will know about it. The duration of the sound alarm is limited in case of temporary absence of the owner. It is possible to organize collective protection - the device has an output to which you can connect the security loop of another device (central console or similar device from a neighbor). When an alarm occurs, this output changes from closed to open (maximum current - 20 mA, voltage when open - not higher than 30 V). It is possible to connect external devices - alerts (siren with current consumption up to 0,3 A) and backup power. The device is powered by a 220 V network, and any 9-volt battery of galvanic cells or a battery with a voltage of 7,5 ... 12 V can be used as a backup power source. Operation is maintained when the voltage drops to 5 ... 5,5 V. With a current consumption of about 15 mA (3 closed loops), a backup source in the form of a Krona battery will last for about 1 days. A set of any sensors and lines with a total resistance of up to 5 kOhm can be used as a security loop (with a wire diameter of 3 m, this a little more than 0,1 km, and at 1 0 mm - about 2 km). The schematic diagram of the security device is shown in fig. one.
Each channel contains an RS flip-flop (in the first channel it is DD1.1), a 2AND-NOT buffer element (DD2.1) and two LEDs: one for indicating the current state of the monitored loop (HL1, HL3, HL5, HL7 green), and the second - to display the break ever occurred (HL2, HL4, HL6, HL8 red glow). Toggle switches SA1-SA5 are shown in the position when the corresponding loops are disabled. In this case, the current does not flow through the security loops, the triggers DD1.1-DD1.4 are in the zero state. The output of the DD3.1 element is high, which prohibits the operation of the divider by 60 of the DD4 microcircuit. The collective security loop (SKO) is closed for the "correct" polarity of the input voltage by the diode VD9. In the operating mode, the SKO is closed by the transistor of the optocoupler U1. Such switching is done to determine the polarity of the cable connection on the opposite side. When one of the loops is armed, a current of about 4 mA flows through it, the corresponding LED is on, and both inputs of the RS trigger are at a low level. Less current can lead to false alarms due to leaks, especially during rain. This continues until the loop is broken (or its resistance increases above 10 kOhm), after which the trigger is activated with a delay of 300 ms, allowing the operation of the alarm LED (HL2. HL4, HL6). RS flip-flop on the elements DD3.1, DD3.2 goes into a low state at the output of the element DD3.1. A high level from the output of DD3.2 opens the transistor VT2, an additional external warning device (siren) is turned on. If the collective protection function was used, then its loop is opened by an optocoupler. Divider by 60 chips DD4 on and time and on expiration 21 s RS-trigger on the elements DD3.1, DD3 2 will return to its original state. However, the triggered channel's LED will remain lit. If the integrity of the loop is restored (this can just be judged by the LED of the current status of the loop), then in order to return to the armed mode on this channel, it is necessary to turn off and on the corresponding loop The mains voltage presence control channel works similarly, except that the role of a normally closed loop is performed (in the presence of mains voltage) by the transistor VT3. The response delay in this channel has been increased to 3 s to eliminate false alarms when starting powerful equipment and welding If more channels are needed, then additional blocks can be connected in parallel with the existing ones (in fact, four original ones are included in this way). This will increase power consumption, which should be considered when choosing a backup power source The dashed lines in the diagram show the option of connecting a 9-volt battery as a backup power source. The device is assembled on two printed circuit boards (Fig. 2 and 3).
If the K176IE12 chip was not found, it can be replaced by the K176IE5 chip by turning it on according to the diagram in fig. 4.
The choice of sound time is carried out by selecting the output of the microcircuit, to which the SB1 button is connected. Instead of a BF1 DEMSh capsule with a resistance of 30 ohms, you can use a dynamic head 0.25GDSH or 0.5GDSH with a resistance of 4 or 8 ohms, turning it on through the output transformer from an old transistor radio. If a piezo emitter from an imported handset-phone is available, it can be turned on according to the diagram in fig. 5.
Toggle switches SA1-SA5 - P2T-1-1V, but you can also use buttons with fixation, for example, P2K, PKn-61. Button SB1 - KM 1-1, connector XS1 - OVTS-VG-5. Diodes VD4-VD7 for a current of at least 0,5 A (KD209 with indices A-B, KD208A or assemblies of the KTs422 series), the rest are any silicon low-power ones. Transistor VT1 must be with a current transfer ratio of at least 100 and a maximum collector current of at least 0,5 A, VT2 - KT972B or KT829 with indices A-G. Optocoupler U1 - AOT127B or 4N33, in the case of using 4N33, the resistor R23 is excluded. The network transformer T1 is suitable for anyone with a voltage of 13 ... 15 V on the secondary winding at a load current of at least 0,1 A. The efficiency of such security systems is 95% determined by the design of intrusion sensors. For two years of operation of this device, the combined method of laying wire extensions has proven itself well (it is assumed that the site is not surrounded by a fence, as a rule, this is a potato plot or cabbage planting). Along the perimeter of the site with an interval of 1,5 ... 2 m, stakes of such a height are stuck that approximately 1-2 m remain above the ground. Stepping back into the territory by 1 ... 2 m, smaller stakes are stuck around the entire perimeter of the plot. It is desirable that they are not visible in the tops, the recommended height is about 40 cm from the ground. A thin copper wire is pulled along the outer stakes (optimally 0,15 mm in diameter, since the thinner one is torn from the wind, and the thick one does not tear, but stretches) in 3 tiers, and along the inner one - in one tier with a thinner wire, about 0,1 . Ø 0 mm. There may be several inner rings, perhaps even wrapping the bushes with wire (in the fall, throw the wire away anyway, since it has already stretched and is replete with breaks). In the garden part, much more imagination is required, the main thing is to make the stretch either irresistible (presumably with a load of someone else's crop), or invisible, or better, both. And one more piece of advice - if you are laying a multi-tiered wire, you should not go all the time in one direction (clockwise or counterclockwise) with a closed perimeter, as a large inductor is formed, which can affect the noise immunity of the system during a thunderstorm. It is better, having reached the beginning when laying along the perimeter, then go in the opposite direction. It should be noted that sometimes stray dogs and crows are troublemakers, both of which often do not notice the wire. Literature
Author: K.Lukyanov, Novosibirsk
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