Security alarm for a farmer. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Security alarm for a farmer. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling

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When I was faced with the need to manufacture such a device, then, having studied a whole stack of literature, I came to the conclusion that none of the previously published schemes is completely suitable for these purposes. Therefore, we had to start manufacturing our own system, which would have simplicity, reliability and at the same time provide protection for several objects remote at a distance of up to 100 m from each other using one security loop. This device can be used to protect a summer house or a garden plot.

The electrical circuit of the security unit is shown in fig. 3.14. It provides an indication of the location of the triggered sensor - one of four, which increases the convenience of its installation and use. You can also determine the place by the nature of the sound of the connected siren or call.

The circuit is sensitive to any violations in the security loop circuit (break or short circuit) and makes it possible to significantly simplify the connection of security objects (see Fig. 3.15).

Rice. 3.14. Electrical diagram of the security unit for connecting remote sensors (click to enlarge)

Security alarm for a farmer
Ris.3.15

The principle of operation of the security unit is based on monitoring the voltage level when a small current flows through the security loop (it changes from triggered sensors).

The circuit is assembled on easily accessible elements and consists of a mains power supply on a T1 transformer and VD3 ... VD6 diodes, a voltage regulator on a D5 chip (KR142EN8B or 142EN8B), a voltage level control circuit on a security loop (VT2 ... VT6) and a shaper time intervals on the chips D1...D4.

The scheme of the shaper of time intervals according to the principle of operation is similar to that shown in fig. 3.10 and has minor differences related to the use of relay K1 to turn on a powerful load (bell or siren, light), as well as LED indication of the type of sensor that has been triggered.

When the security unit is turned on (by switch SA1), the circuit provides a delay in setting the ARMED mode by 12 seconds so that the owner has time to leave the premises.

When entering the house, the F5 sensor will be triggered, and within 6 seconds it is necessary to turn off the alarm before the sound alert appears.

The entire circuit in the SECURITY mode consumes a current of no more than 25 mA through the +10 V circuit, and with an error-free assembly, its setting consists in setting the resistor R12 (multi-turn, type SP5-2) log. "1" on the VT4 collector, and when the F2 or F3 sensors are triggered, a log should appear. "0".

Relay K2 should only work if the security loop is short-circuited (sensor F4 has tripped).

Table 3.1
State of the security loop Triggered sensor Glow of LEDs in the security unit Circuit breakpoints Output signal to turn on relay K1
HL1 HL2 HL3 а b с
"GUARD" mode - no no no 1 1 1 no
loop break F1 Yes Yes no 1 0 1 break incl. relay alternates with cont.
sensor short circuit F2 or F3 no no no 0 1 0 continuous on interspersed with pauses
sensor short circuit F5 Yes no no 0 1 1 continuous on interspersed with pauses
loop closure F4 no no Yes 0 0 0 continuous switching

For the convenience of setting up the circuit, Table 3.1 is given, which allows you to understand the logic of the circuit and the indication of the triggered sensor.

In the manufacture of the circuit, capacitors C1, C3, C4, C6 of the K10-17a type were used; C2, C5 - K50-35A for 50 V. Instead of transistors VT3, VT5, VT6, you can use a 1NT251 transistor matrix. Relay K1 type REN34 HP4.500.000-01; K2 - RES55A RS4.569.602 (or RS4.569.607) or RES55B RS4.569.627 (RS4.569.632) for an operating voltage of 12 V.

Any transformer T1 can be used with a voltage in the secondary winding of 18 ... 25 V. This voltage is found in many transformers from household radio equipment. So, for example, many of the unified type transformers are suitable: TPP221 ... TPP226, TPP231 ... TPP236, TPP245 ... TPP248, TPP251 ... TPP262 and others. They have many secondary windings with different voltages, and connecting them in series will allow you to get the right one.

As sensors F1...F5, it is better to use reed contacts in conjunction with magnets, since they are sealed and not afraid of atmospheric influences.

The use of the SA2 switch is not mandatory, but its presence makes it convenient (silent) to check the operation of the security unit during operation.

Publication: cxem.net

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