Apartment alarm. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling
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The "armed" alarm is activated 3 ... 5 minutes after the SA1 "On" toggle switch is closed, so that during this time you can safely leave the apartment and close the door. When the door is opened, it also works with a delay sufficient to turn off the device (20...30 s).
(click to enlarge)
When the SA1 toggle switch is turned on, the mains voltage is supplied to the power supply unit (T1, VD1 ... VD4, C1), from which a constant voltage of 24 V is supplied to the time relay. After 3 ... 5 minutes (the exposure time depends on the resistance of the resistor R2 and the capacitance of the capacitor C2), the voltage on C2 reaches the opening voltage of the zener diode VD6, VT1 opens and relay K1 is activated. With contacts K1.1, it is self-locking, and through K1.2 it supplies power to relay K2, connected in series with the contacts on the front door of the apartment. Now, even with a short opening of the door (closing B1), relay K2 is activated, blocks itself with contacts K2.1, and through contacts K2.2 and K2.3 supplies power to the second time relay, similar to the first. Now, if the SA1 toggle switch is not turned off in time, after 20 s (depending on the resistance R4 and the capacitance C3), relay K3 will work, contacts K3.1 will be blocked, and contacts K3.2 ... K3.4 will turn on the signaling device. When the power is turned off with the SA1 toggle switch, the device returns to its original state. Resistors R1, R3 and diodes VD5 and VD8 serve to quickly discharge the capacitors in the time relay after the power is turned off. Relay K1 ... KZ - type RES-22 or others, with windings for 24 V. Transistors VT1 and VT2 - any with a maximum allowable voltage of at least 24 V.
Establishing the system is reduced to the selection of ratings R2, C2 and R4, C3 to set the required response time.
As a signaling device, you can use a "howler" or a loud bell. A good effect will also be the connection of a stroboscope on an MTX-90 lamp. You can also use a simple generator on a relay, the contacts of which are connected in parallel with the light switch, for example, in the hallway, so that the light turns on and off at a frequency of 1 ... 2 Hz.
With an unexpected simultaneous activation of calls, a strobe light or a "blinking light", the first thing the "uninvited guests" will think about is to get out of the apartment as quickly as possible.
With a large number of all kinds of calls, the K3 relay will have to be replaced with another one with more powerful contacts, or another, more powerful one, which, in turn, will control signaling devices, will be switched on through its contacts.
Author: A. Lysunets, v. Vozzhaevka, Amur Region; Publication: N. Bolshakov, rf.atnn.ru
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