one time only burglar alarm

This alarm is designed to activate its siren only once. When the alarm is triggered, the siren will sound for a predetermined duration before turning off completely. The alarm will not reactivate automatically. The basic circuit features a single zone with independently adjustable exit and entry delays. This zone is compatible with various types of input devices, including normally-open and normally-closed configurations such as pressure mats, magnetic reed contacts, micro switches, foil tape, and passive infrared sensors (PIRs). A selection of expansion modules can be added to incorporate additional instant alarm zones, personal attack zones, and tamper zones into the system. Additionally, there is an untimed output module that can maintain an internal sounder, strobe light, lamp, or similar device after the siren has ceased. The alarm can be controlled via a discreet two-way switch, such as a light switch, or with a key switch for enhanced security, or through various code-operated keypad switches. Prior to activating the alarm, it is essential to ensure that the premises are secure, indicated by all green LEDs being lit and the yellow LED being off. If the yellow LED is illuminated, it signifies a fault in one of the zones, preventing the alarm from being set. Depending on the setting of resistor R9, when the switch (Sw1) is moved to the "set" position, there is a grace period of approximately one minute to exit the building. Upon return and opening the door, a buzzer will sound. Depending on the setting of resistor R8, there is also a time limit of about one minute to deactivate the alarm. Failing to do so will result in the siren sounding. The duration of the siren can be set with resistor R14, allowing it to sound for up to approximately 20 minutes before turning off completely. The alarm can be silenced at any time by moving Sw1 to the "off" position.

The alarm system operates on a straightforward electronic circuit that integrates various components for functionality and reliability. The main unit includes a microcontroller that manages alarm states and timing sequences. Input devices connect to the microcontroller through a series of input terminals, allowing for both normally-open and normally-closed configurations. The adjustable exit and entry delays are accomplished using timing circuits that are influenced by the settings of resistors R8 and R9, which can be calibrated to suit user preferences.

Expansion modules connect to the main circuit board through dedicated connectors, enabling the addition of more alarm zones without significant redesign. Each expansion module is designed to interface seamlessly with the main unit, utilizing a standardized communication protocol to ensure compatibility and ease of installation.

The untimed output module is particularly useful for applications requiring continuous alert signals after the initial alarm event. This module can be used to trigger strobe lights or other visual indicators, enhancing the alarm's effectiveness in alerting occupants and deterring intruders.

The alarm's activation and deactivation are managed through a simple switch mechanism, with options for enhanced security through key switches or keypad interfaces. The use of visual indicators, such as green and yellow LEDs, provides immediate feedback to the user regarding the system's status, ensuring that the premises can be secured effectively.

Overall, this alarm system is designed to provide a robust and user-friendly security solution, with flexibility for expansion and customization based on specific user needs and security requirements.This alarm is designed to sound its Siren only once. That is - when the alarm is activated - the Siren will sound for a preset length of time. Then it will switch off and remain off. The alarm will not re-activate. The basic circuit has a single zone with independently adjustable Exit and Entry delays. The zone will accommodate the usual types of normally-open and normally-closed input devices - such as pressure mats, magnetic-reed contacts, micro switches, foil tape and PIRs. A range of Expansion Modules allow you to add any number of Instant Alarm Zones, Personal Attack Zones and Tamper Zones to your system.

There`s also an Untimed Output Module. It will keep an internal sounder, strobe-light, lamp or whatever going after the siren has stopped. The alarm may be operated by a simple hidden two-way switch - such as a light switch. If you want more security - you can use a key switch - or one of a number of code operated Keypad Switches. Before you set the alarm - make sure that the building is secure - that ALL of the Green LEDs are lighting - and that the Yellow LED is off.

If the Yellow LED is lighting - there`s a fault in one of the zones - and THE ALARM WILL NOT SET. Depending on the setting of R9 - when you move Sw1 to the "set" position - you have up to about a minute to leave the building. When you return and open the door - the Buzzer will sound. Depending on the setting of R8 - you have up to about a minute to switch the alarm off. If you fail to do so - the Siren will sound. Depending on the setting of R14 - the Siren will sound for up to about 20-minutes. Then it will switch off - and remain off. Of course - you can stop the noise at any time by moving Sw1 to the "off" position. 🔗 External reference