Selasa, 20 November 2012

Multi-Zone Transistor Alarm

Notes:
It's easy to use. Make sure that the green LED is lighting - then switch the alarm on using Sw1. You have about 30 seconds to leave the building. When you return and open the door - the Buzzer will sound. You have about 30 seconds to switch off the alarm. If you fail to do so - the Siren will sound.

While at least one of the trigger switches remains open - the Siren will continue to sound. However - if the trigger circuits have been restored - the alarm will reset itself after about 10 minutes. Of course - you can turn the Siren off at any time by switching off the alarm.

Because of manufacturing tolerances - the precise length of any delay depends on the characteristics of the actual components you've used in your circuit. But - to some degree - by altering the values of R2, R7 & R9 you can adjust the Exit, Entry and Reset times to suit your requirements. Increasing the values increases the time - and vice-versa.

If you don't want the "Instant" zone - leave out D7, D8, D9, R12, R13, C8 and the Green LED.

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