1. The Hall Effect Sensor Rene Dupuis

2. Background Information The Hall effect was discovered by Edwin Hall in 1879; “electron” was not experimentally discovered; had to wait until quantum mechanics came Development of semiconductor compounds in 1950's led to first useful Hall effect magnetic instrument In the 1960's, first combinations of Hall elements and integrated amplifiers Resulted to classic digital output Hall switch Resulted to classic digital output Hall switch In 1965, first low-cost solid state sensor In 1965, first low-cost solid state sensor

3. 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

4. Basic Hall Effect Sensor Hall element Hall element is the basic magnetic field sensor Differential Amplifier Differential Amplifier amplifies the potential difference (Hall voltage) Regulator Regulator holds current value so that the output of the sensor only reflects the intensity of the magnetic field

5. BOP — Operate point A positive magnetic field > BOP will switch the sensor on (output low). A positive magnetic field > BOP will switch the sensor on (output low). BRP — Release point Removal of the magnetic field < BRP will switch the sensor off (output high). Removal of the magnetic field < BRP will switch the sensor off (output high). Bhys — Hysteresis UnipolarLatchingBipolar Types Magnetic Parameters

6. Unipolar 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 BRP

7. Latching Require both positive and negative magnetic fields Symmetrical Duty Cycle operation Guaranteed power-up state >BOP or <BRP

8. Bipolar Involves either Unipolar or Latching characteristics Same principle Unipolar Mode Latching Mode

9. Sensor switch operation Power-up states

10. Hall Effect Sensor Example

11. 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.

12. 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)

13. Benefits 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

14. Prices and Sources Range from $1-$60 Allied Electronics AllegromicroDigi-Key

15. Sensor Indicates Direction Output Rotational or Linear Notes Optical Incremental EncodersYes Digital (Quadrature) Both Uses light and optics to sense motion InterruptersNo Digital (Single Pulse) Rotational Senses light with light beam interrupt Photo- reflective sensorsNoDigital(Single Pulse)Linear Generates pulse whenever sensor receives reflected light Laser InterferometerYes Digital (Quadrature) Linear Laser supply linear displacement of an object Triangulation SensorsYesAnalogLinear Laser supply non-contact linear displacement of an object Hall-Effect Sensors No Digital (Single Pulse) Rotational

16. QUESTIONS?