Security-door-ajar-alarm
The TL3019 device activates, or goes low, when a south pole of a magnet approaches the chip face. In this example, there are five doors, each equipped with a magnet embedded in its edge, with the south pole facing outward. A TL3019 sensor is positioned in the door jamb at the location of the magnet when the door is closed. With the doors closed, the Hall effect devices remain in a logic low state. This design incorporates five doors and utilizes five TL3019 devices. Each TL3019 is connected in series with a 4 kΩ resistor, and all door sensor and resistor sets are arranged in parallel to the inverting input of an LM393 comparator. When all doors are closed, the effective resistance approximates 800 Ω, resulting in a voltage of 2.2 V at the inverting input. The non-inverting input is connected to a voltage divider network that establishes the reference voltage. A 1.5 kΩ potentiometer is adjusted to ensure the indicator is off when all doors are closed, producing a voltage of 2.35 V at the non-inverting input of the comparator. Upon opening a door, the voltage at the inverting input rises to 2.5 V, exceeding the reference voltage, causing the LED to illuminate. This circuit design allows for monitoring multiple doors and windows and can be expanded to include an audible alarm alongside the visual LED indicator.
The TL3019 Hall effect sensor operates based on the principle of detecting magnetic fields, specifically the presence of a south pole magnet. When the south pole approaches the sensor, it triggers a change in the output state from high to low, indicating that the door is closed. This feature is particularly useful in security applications where monitoring the status of multiple entry points is essential.
In this configuration, the five TL3019 sensors are strategically placed within the door frames, ensuring reliable detection of door positions. The inclusion of a 4 kΩ resistor in series with each sensor helps to limit the current flowing through the circuit, protecting the components and ensuring proper operation. The parallel arrangement of these sensor-resistor sets allows for a collective response to the status of the doors, simplifying the wiring and reducing complexity.
The LM393 comparator plays a critical role in interpreting the output from the sensors. With its dual input configuration, it compares the voltage levels from the inverting and non-inverting inputs. The reference voltage established by the voltage divider network is crucial for determining the threshold at which the LED indicator activates. The adjustable 1.5 kΩ potentiometer provides flexibility in setting this threshold, allowing for fine-tuning based on the specific requirements of the installation.
When a door opens, the voltage at the inverting input increases, surpassing the reference voltage. This transition triggers the comparator to switch its output state, illuminating the LED and signaling that the door is no longer closed. The design's scalability is a notable advantage, enabling the addition of more sensors for additional doors or windows without significant redesign.
Furthermore, integrating an audible alarm can enhance the system's functionality, providing an immediate alert when a door is opened. This feature can be particularly beneficial in security applications, where timely notifications are essential for maintaining safety. Overall, this circuit design demonstrates an effective approach to monitoring multiple entry points, leveraging the capabilities of Hall effect sensors and comparators to create a reliable and efficient system.In operation, the TL3019 device will activate, or become low, when a south pole of a magnet comes near the chip face of the device. The example shows five doors. Each door has a magnet embedded in its edge with the south pole facing the outer surface. At the point where the magnet is positioned with the door closed, a TL3019 sensor is placed in the door jamb.
With the door closed, the Hall devices will be in a logic low state. This design has five doors and uses five TL3019 devices. Each TL3019 has a 4-KO resistor in series and all door sensor and resistor sets are in parallel and connected to the inverting input of an LM393 comparator. With all doors closed, the effective resistance will be about 800 0-and produce 2.2 V at the inverting input.
The noninverting input goes to a voltage divider network which sets the reference voltage. The 1.5-KO potentiometer is adjusted so the indicator goes out with all doors closed. This will cause 2.35 V to appear at the noninverting input of the comparator. When a door opens, the voltage at the inverting input will go to 2.5 V which is greater than VRm and the LED will light. A large number of doors and windows can be monitored with this type of circuit. Also, it could be expanded to add an audible alarm in addition to the visual LED.
The TL3019 Hall effect sensor operates based on the principle of detecting magnetic fields, specifically the presence of a south pole magnet. When the south pole approaches the sensor, it triggers a change in the output state from high to low, indicating that the door is closed. This feature is particularly useful in security applications where monitoring the status of multiple entry points is essential.
In this configuration, the five TL3019 sensors are strategically placed within the door frames, ensuring reliable detection of door positions. The inclusion of a 4 kΩ resistor in series with each sensor helps to limit the current flowing through the circuit, protecting the components and ensuring proper operation. The parallel arrangement of these sensor-resistor sets allows for a collective response to the status of the doors, simplifying the wiring and reducing complexity.
The LM393 comparator plays a critical role in interpreting the output from the sensors. With its dual input configuration, it compares the voltage levels from the inverting and non-inverting inputs. The reference voltage established by the voltage divider network is crucial for determining the threshold at which the LED indicator activates. The adjustable 1.5 kΩ potentiometer provides flexibility in setting this threshold, allowing for fine-tuning based on the specific requirements of the installation.
When a door opens, the voltage at the inverting input increases, surpassing the reference voltage. This transition triggers the comparator to switch its output state, illuminating the LED and signaling that the door is no longer closed. The design's scalability is a notable advantage, enabling the addition of more sensors for additional doors or windows without significant redesign.
Furthermore, integrating an audible alarm can enhance the system's functionality, providing an immediate alert when a door is opened. This feature can be particularly beneficial in security applications, where timely notifications are essential for maintaining safety. Overall, this circuit design demonstrates an effective approach to monitoring multiple entry points, leveraging the capabilities of Hall effect sensors and comparators to create a reliable and efficient system.In operation, the TL3019 device will activate, or become low, when a south pole of a magnet comes near the chip face of the device. The example shows five doors. Each door has a magnet embedded in its edge with the south pole facing the outer surface. At the point where the magnet is positioned with the door closed, a TL3019 sensor is placed in the door jamb.
With the door closed, the Hall devices will be in a logic low state. This design has five doors and uses five TL3019 devices. Each TL3019 has a 4-KO resistor in series and all door sensor and resistor sets are in parallel and connected to the inverting input of an LM393 comparator. With all doors closed, the effective resistance will be about 800 0-and produce 2.2 V at the inverting input.
The noninverting input goes to a voltage divider network which sets the reference voltage. The 1.5-KO potentiometer is adjusted so the indicator goes out with all doors closed. This will cause 2.35 V to appear at the noninverting input of the comparator. When a door opens, the voltage at the inverting input will go to 2.5 V which is greater than VRm and the LED will light. A large number of doors and windows can be monitored with this type of circuit. Also, it could be expanded to add an audible alarm in addition to the visual LED.