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One-Time Burglar Alarm Schematic: Build Your Security System
Description
This alerting device is engineered to emit its Buzzer only once. Specifically, once the device is activated, the Buzzer will operate for a duration predetermined beforehand. Subsequently, it will cease operation and remain inactive. The device will not re-initiate its signal.
The fundamental alerting system incorporates a single monitored area with independently configurable Entry and Exit delays. This area is compatible with a variety of routinely-utilized normally-open and normally-closed input devices - such as pressure sensors, magnetic reed switches, miniature switches, foil tape, and passive infrared (PIR) detectors.
A selection of Expansion Modules enables the addition of any desired quantity of Instant Alert Areas, Personal Attack Areas, and Tamper Areas to the overall system. There is also a Module without Timing, which will maintain an internal sounder, strobe-light, lamp, or comparable component operational even after the Buzzer has concluded its signal.
Integrated Circuit Details
The system utilizes an LM380 integrated circuit (IC) for the Buzzer output. This IC is a low-power, three-terminal adjustable linear regulator, commonly employed in audio amplification circuits due to its ability to provide a stable and amplified signal. The LM380 is known for its simple circuitry and efficiency, making it a suitable choice for generating the audible alert signal in this alarm system. The IC's ability to control the current flowing through the Buzzer ensures a consistent and reliable output, contributing to the overall functionality of the system. The device incorporates a 10k resistor for current limiting and a 100-ohm resistor for the speaker.
Schematic Diagram
The alerting device can be activated using a basic, concealed two-way switch, such as a standard light switch. For enhanced security, a key switch, or one of several code-operated Keypad Switches can be utilized.
Prior to setting the alerting device, ensure that the building is securely protected, that ALL of the Green LEDs are illuminated, and that the Yellow LED is extinguished. If the Yellow LED is illuminated, there is a fault within one of the areas, and THE ALARM WILL NOT SET.
Depending on the configuration of R9 – when Sw1 is moved to the “set” position, you have approximately one minute to vacate the building. Upon your return and door opening, the Buzzer will sound. Depending on the configuration of R8, you have approximately one minute to deactivate the alerting device. If this timeframe expires, the Siren will sound.
Depending on the configuration of R14, the Siren will operate for a maximum duration of approximately 20 minutes. Following this period, it will automatically cease operation and remain inactive. Of course, you can interrupt the noise at any time by moving Sw1 to the “off” position.
Upon your return, if the Buzzer does not sound and the Yellow LED is illuminated, then there has been an activation event while you were absent.
Stripboard Layout
Parts list
