6 Zone Alarm System

  
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This alarm system has 6 independent zones, 1 timed entry/exit zone, a 7 segment LED display and a test or walkthrough facility. Suitable for a small office or home environment, it can also be adapted to use a combination lock or keypad to set and reset the alarm. Please Note: All orange +V terminals connect to the point marked +5V at the side of t
6 Zone Alarm System - schematic

he set switch, S1. IC`s U1, U2, U3, U4, U5 and U7 are drawn without power connections for clarity. The power connections need to go +5V and ground. See Practical Section for IC pinouts and relay contacts. All zones Z1 to Z6 use normally closed alarm contacts. Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 to 6 are immediate zones, which will trigger the alarm with no delay. Some RF immunity is provided for long wiring runs by the input capacitors, C1 - C6. The key switch, S1 acts as the Set and Reset/Unset switch. For best security this should be the metal type switch with a key. All IC`s except IC6 are CMOS types with buffered outputs, these are denoted by the suffix "B". Unbuffered CMOS IC`s have a suffix starting "U" and will not work in this circuit. IC6 is a 5 Volt regulator providing power to the main CMOS IC`s, the alarm power supply can be any suitable 12 to 15V power supply. In operation the DPDT switch S2 is set to the "run" position. When keyswitch S1 is turned reset, this is the unset (off) state of the alarm. In this condition capacitor C8 will discharge via D9, R1 and Z1 and capacitor C7 will have discharged via D8, R17 and S1. Relay RLY1 will not be energized and all CMOS IC`s and the display will have no power. When S1 is turned to set all CMOS IC`s receive 5 Volt power. C11 will briefly charge and apply a low input signal to one half of U7A a CMOS4001B, a dual...



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