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The Hall Effect SensorThe Hall Effect Sensor
Rene DupuisRene Dupuis
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Background InformationBackground Information
The Hall effect was discovered by Edwin Hall The Hall effect was discovered by Edwin Hall in 1879; “electron” was not experimentally in 1879; “electron” was not experimentally discovered; had to wait until quantum discovered; had to wait until quantum mechanics came mechanics came Development of semiconductor compoundsDevelopment of semiconductor compoundsin 1950's led to first useful Hall effect magneticin 1950's led to first useful Hall effect magneticinstrumentinstrumentIn the 1960's, first combinations of Hall In the 1960's, first combinations of Hall elements and integrated amplifiers elements and integrated amplifiers
Resulted to classic digital output Hall switchResulted to classic digital output Hall switch In 1965, first low-cost solid state sensorIn 1965, first low-cost solid state sensor
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Theory of the “Hall Effect”Theory of the “Hall Effect”Hall effect principle, no magnetic field
Hall effect principle, magnetic field present
Potential Difference (voltage) across output:
V = I * B
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Basic Hall Effect SensorBasic Hall Effect Sensor
Hall elementHall element is the basic magnetic field sensor
Differential AmplifierDifferential Amplifier
amplifies the potential difference (Hall voltage)
RegulatorRegulator holds current value so that the output of the sensor only reflects the intensity of the magnetic field
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BOP — Operate pointBOP — Operate point A positive magnetic A positive magnetic
field > BOP will switch field > BOP will switch the sensor on (output the sensor on (output low). low).
BRP — Release pointBRP — Release point Removal of the Removal of the
magnetic field < BRP magnetic field < BRP will switch the sensor will switch the sensor off (output high). off (output high).
Bhys — HysteresisBhys — Hysteresis
UnipolarUnipolar
LatchingLatching
BipolarBipolar
Types Magnetic Parameters
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UnipolarUnipolar
Requires single polarity magnetic field for operation
Positive magnetic field (South pole)
Directed towards branded face of the sensor for activation
True-Power-On State <BOP or >BRP
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LatchingLatching
Require both positive and negative magnetic fields
Symmetrical Duty Cycle operation
Guaranteed power-up state
>BOP or <BRP
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BipolarBipolarInvolves either Unipolar or Involves either Unipolar or Latching characteristicsLatching characteristics
Same principleSame principle
Unipolar Mode
Latching Mode
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Sensor switch operation
Power-up states
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Hall Effect Sensor ExampleHall Effect Sensor Example
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Application: Response to South or North Polarity
Motor-Tachometer application where each rotation of the motor shaft is to be detected
When ring magnet rotates w/ motor, South Pole passes the sensing face of the Hall sensor after each revolution.
Sensor Actuated when the South Pole
approaches sensor Deactuated when South Pole
moves away from sensor
Single digital pulse produced for each revolution.
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Application: Gear Tooth Sensing
• Sensor detects change in flux level • Translates it into a change in the sensor output (high to low)
• Sense movement of ferrous metal targets (magnetically biased)
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BenefitsBenefits
Small and rugged non-contact sensors
Insensitive to oil, dirt, humidity and dust
High magnetic sensitivity Accurate and Reliable
Delivers low Power consumption
Supply voltage capability
Average current consumption
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Prices and SourcesPrices and Sources
Range from $1-$60Range from $1-$60
Allied ElectronicsAllied Electronics
Allegromicro Allegromicro
Digi-KeyDigi-Key
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SensorSensor IndicateIndicatessDirectioDirectionn
OutputOutput RotationalRotationalor Linearor Linear
NotesNotes
Optical Incremental Encoders
YesYes Digital Digital
(Quadrature)(Quadrature) BothBoth Uses light and Uses light and
optics to sense optics to sense motionmotion
Interrupters NoNo Digital Digital
(Single Pulse)(Single Pulse) RotationalRotational Senses light Senses light
with light beam with light beam interruptinterrupt
Photo-reflective sensors
NoNo Digital Digital
(Single Pulse)(Single Pulse)
LinearLinear Generates Generates pulse whenever pulse whenever sensor receives sensor receives reflected light reflected light
Laser Interferometer
Yes Yes Digital Digital (Quadrature)(Quadrature)
LinearLinear Laser supply Laser supply linear linear displacement of displacement of an objectan object
Triangulation Sensors
YesYes AnalogAnalog LinearLinear Laser supply Laser supply non-contact non-contact linear linear displacement of displacement of an objectan object
Hall-Effect Hall-Effect SensorsSensors
NoNo Digital Digital (Single Pulse)(Single Pulse)
RotationalRotational
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QUESTIONS?QUESTIONS?