Hall Sensor can be used as a Magnetic Proximity sensor to Switch On/Off circuits or in combination with electronic door lock. The Hall sensor is a semiconductor device and its output depends on the presence of absence of a strong magnetic field. Hall sensor HSI MH183 is used in the circuit to demonstrate the working of Hall Sensors. MH 183 is a unipolar Hall effect sensor IC. It incorporates advanced chopper stabilization technology to provide accurate and stable magnetic switch points. The design, specifications and performance have been optimized for applications of solid state switches. HIS MH183 has a transistor at the output which sinks current in the presence of strong South Pole magnetic field. Output turns high if the magnetic field weak and turns off if there is no magnetic field.
The output of Hall sensor is connected to the base of a PNP transistor BC557 so in the presence of magnetic field, it will turn on causing T2 off. LED remains off and indicates the presence of Magnet close to the Hall sensor and the stand by state. When the magnet move away, output of hall sensor turns high if the magnetic field is weak. T1 then turns off and T2 conducts. LED lights to indicate the weak magnetic field. If there is no magnetic field, the output of hall sensor remains off.