5 Zone Alarm Circuit

Each zone uses a normally closed contact. These can be micro switches or standard alarm contacts (usually reed switches). Zone 1 is a timed zone which must be used as the entry and exit point of the building. Zones 2 - 5 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-C5. C7 and R14 also form a transient suppresser. The key switch acts as the Set/Unset and Reset switch. For good security this should be the metal type with a key. At switch on, C6 will charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by varying either C6 or R11. Once the timing period has elapsed, LED6 will light, meaning the system is armed. LED6 may be mounted externally (at the bell box for example) and provides visual indication that the system has set. Once set any contact that opens will trigger the alarm, including Zone 1. To prevent triggering the alarm on entry to the building, the concealed re-entry switch must be operated. This will discharge C6 and start the entry timer. The re-entry switch could be a concealed reed switch, located anywhere in a door frame, but invisible to the eye. The panic switch, when pressed, will trigger the alarm when set. Relay contacts RLA1 provide the latch, RLA2 operate the siren or buzzer.

Electronic Combination Lock Circuit

This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit will reset and you will need to start over. Depending on how you wire the switches, you can use any 4 switch combination.