hall effect sensor.ppt

8/10/2019 Hall Effect Sensor.ppt

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The Hall Effect Sensor

Rene Dupuis


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Background Information

The Hall effect was discovered by Edwin Hallin 1879; electron was not experimentallydiscovered; had to wait until quantummechanics came

Development of semiconductor compoundsin 1950's led to first useful Hall effect magneticinstrumentIn the 1960's, first combinations of Hall

elements and integrated amplifiers Resulted to classic digital output Hall switch In 1965, first low-cost solid state sensor


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Theory of the Hall EffectHall 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 Sensor

Hall elementis the basicmagnetic field sensor

Differential Amplifieramplifies the potentialdifference (Hall voltage)

Regulatorholds currentvalue so that the output of thesensor only reflects the

intensity of the magnetic field


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BOP Operate point A positive magnetic

field > BOP will switchthe sensor on (output

low).

BRP Release point

Removal of themagnetic field < BRPwill switch the sensoroff (output high).

Bhys Hysteresis

Unipolar

Latching

Bipolar

Types Magnetic Parameters


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Unipolar

Requires single polaritymagnetic fieldfor operation

Positive magnetic field

(South pole)Directed towards brandedface of the sensor foractivation

True-Power-On State

BRP


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Latching

Require both positiveand negative magneticfields

Symmetrical Duty Cycleoperation

Guaranteed power-upstate

>BOP or


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Bipolar

Involves either Unipolar orLatching characteristics

Same principle

Unipolar Mode

Latching Mode


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Sensor switch operation

Power-up states


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Hall Effect Sensor Example


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Application: Response to South orNorth Polarity

Motor-Tachometer applicationwhere each rotation of themotor shaft is to be detected

When ring magnet rotates w/

motor, South Pole passes thesensing face of the Hall sensorafter each revolution.

Sensor Actuated when the South Pole

approaches sensor Deactuated when South Pole

moves away from sensor

Single digital pulse producedfor each revolution.


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Application: Gear Tooth Sensing

Sensor detects changein flux levelTranslates it into achange in the sensor

output (high to low)

Sense movement offerrous metal targets(magnetically biased)


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Benefits

Small and rugged non-contact sensors

Insensitive to oil, dirt, humidity and dust

High magnetic sensitivityAccurate and Reliable

Delivers lowPower consumption

Supply voltage capability

Average current consumption


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Prices and Sources

Range from $1-$60

Allied Electronics

Allegromicro

Digi-Key


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QUESTIONS?

hall effect sensor.ppt

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