How to build a CMOS single zone alarm
Explanation
The circuit has automatic access delays-meter clock cutoff-and system reset. It provides for normally open and normally closed switches-and will satisfy the usual input devices (pressure pads, magnetic spring contacts, aluminum foil tape, PIRs and inertial sensors). Welcome to reprint, this article comes from the electronic enthusiast network (http: //)
If the green indicator light does not light-an open window or door etc. is checked once, the building is safe-and the green LED lighting-SW1 moves to the "set" position. Just then-the red LED will light up-and the exit delay will start. The length of the channel exit delay is determined by the value of R12.
With a 220k resistance-you have about 30 to 40 seconds to leave. When you do this-the buzzer will sound. It should stop sounding when you close the door behind you. This indicates that the circuit has been successfully restored within the time allowed.
When you return to the building, open the door-the buzzer sound-and the entry delay will begin. With a 470k resistor you have about 30 to 40 seconds to put SW1 to the "off" position. If you do not do this-the alarm will sound. Call the police
The length of time the sound is made by R11. With a 4M7 resistor it will sound about 15 to 20 minutes. Then, the relay will exit-and the alarm will try to reset itself. It's simple by using Season 3 to "turn off" the switch itself.
If the trigger circuit has been restored-the alarm is reset. If not-the attempt will fail-and the alarm will be reactivated. It will continue to try to reset itself every 15 to 20 minutes-until the trigger circuit is restored-or the alarm is turned off.
All common triggering devices may be connected to the input terminals. These measures include inertial sensors. The sensitivity of the sensor is adjusted by R4. Set to the lowest value-the alarm will be activated.
If you are not using an inertial sensor-replace it with a 220k fixed resistor R4. If you don't use a normally open switch-you can omit R1, C1-but you must adapt to the extra connection between the green LED and C2. Welcome to reprint, this article comes from the electronic enthusiast network (http: //)
layout
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