Magnetic Door Alarm Circuit using Hall Sensor

The door alarm is a very popular protection system and is useful. They are used to see whether the Door is open or locked. We have also noticed any door sensor in the fridge creating a distinct sound when they activate.

A Hall sensor is an instrument that can sense a magnet depending on its polarity. It is a transducer, which produces a signal according to the nearby magnetic field. We used a 3144 Hall Effect Sensor here which has a range of about 2 cm. As the name implies the Hall Effect Sensor operates with the "Round Effect" concept. Under this rule, “when a conductor or semiconductor with current flowing in one direction was introduced perpendicular to a magnetic field a voltage could be measured at right angles to the current path”.

Hardware Component

The following components are required to make Magnetic Door Alarm Circuit

NE555 IC Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer

LM7805 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of LM7805 

Magnetic Door Alarm Circuit

Working Explanation

It's hard to operate on the Magnetic Door Detector. Here, as we have already described, we have built a 555-astable multi-vibrator for generating an alarm signal. However, we monitor this astable multi-vibrator U2 through a Q1 BC547 NPN transistor using Hall Sensor U3. When we place the magnate next to Hall Sensor, the hall sensor detects the magnetic field and produces a weak output signal.

This performance goes to the transistor foundation. The transistor stays shut off owing to the weak signal, control is not supplied to the 555 timer IC, and the buzzer remains quiet with the Lead turned off.

Application and Uses

• Popular and versatile protection device. Those are used to determine whether the door is open or closed