Hall Effect Sensors - mechatronics

Hall Effect Sensors
Daniel Morgan
ECE 5320
HW #01

• Reference list
• To probe further
• Major applications
Outline
• Basic working principle illustrated
• A typical sample configuration in application
(application notes)
• Major specifications
• Limitations
• And many more relevant issues in applications
• Conclusion

References
http://www.sensorland.com/HowPage046.html
http://www.micronas.com/products/overview/sensor
• Isolated Open Loop Current Sensing Using Hall
Effect Technology in an Optimized Magnetic Circuit,
Richard Dickinson & Shaun Milano, Allegro
MicroSystems, Inc.
• Understanding Bipolar Hall-Effect Sensors, by Joe
Gilbert, Allegro MicroSystems, Inc.
• http://www.allegromicro.com/techpub2/an/an27705.pdf
• http://www.eeel.nist.gov/812/effe.htm#lore
• http://www.allaboutcircuits.com/vol_2/chpt_13/6.html

http://digi-key.com
References
http://www.electronicscomponentsworld.com/art
icleView~idArticle~71786_2303944122472007.
html

To Probe Further
http://www.physics.gatech.edu/advancedlab/lab
s/hall/
http://www.allegromicro.com/techpub2/an/an27
705.pdf
http://www.techfak.unikiel.de/matwis/amat/elmat_en/kap_1/backbone/
r1_3_4.html
http://hyperphysics.phyastr.gsu.edu/hbase/magnetic/hall.html

To Probe Further
http://en.wikipedia.org/wiki/Hall_effect
http://en.wikipedia.org/wiki/Hall_effect_thruster

RPM Sensing
Drive by Wire
Brake by Wire
Major Applications
Distance measurement
Push Button Switches
Current Limit Switches
Disk Drives
Ignition Systems

Basic Working Principle
Illustrated
“This transverse voltage is
the Hall voltage VH and its
magnitude is equal to
IB/qnd, where I is the
current, B is the magnetic
field, d is the sample
thickness, and q (1.602 x
10-19 C) is the elementary
charge. In some cases, it
is convenient to use layer
or sheet density (ns = nd)
instead of bulk density.
One then obtains the
equation ns = IB/q|VH|

Basic Working Principle
Illustrated (Continued)
Thus, by measuring the Hall voltage VH and from the
known values of I, B, and q, one can determine the
sheet density ns of charge carriers in semiconductors.
If the measurement apparatus is set up as described
later in Section III, the Hall voltage is negative for ntype
semiconductors and positive for p-type
semiconductors. The sheet resistance RS of the
semiconductor can be conveniently determined by use
of the van der Pauw resistivity measurement
technique. Since sheet resistance involves both sheet
density and mobility, one can determinne the Hall
mobility from the equation µ = |VH|/RSIB = 1/(qnSRS)

Basic Working Principle
Illustrated (Continued)
If the conducting layer thickness d is known,
one can determine the bulk resistivity (r = RSd)
and the bulk density (n = nS/d).

Typical Sample Configuration-
RPM Sensing
Hall Effect Sensors
can be used to sense
RPM in a number of
applications
Brushless DC Motor
Each stator has a hall
effect sensor on it to
allow for greater
accuracy

Typical Sample Configuration-
RPM Sensing
RPM Sensing in automotive applications

Typical Sample Configuration-
RPM Sensing
1.)
2.)
3.)

Typical Sample Configuration-
Rotational Velocity
Used to determine
Rotational Velcity
Records timing of
switching from N to S
poles
Uses above
information to
determine rotational
velocity.

Typical Sample Configuration-
Spacecraft Propulsion
A Hall effect thruster is a type
of ion thruster in which the
propellant is accelerated by
an electric field in a plasma
discharge with a radial
magnetic field. Also known
simply as plasma thrusters,
HETs use the Hall effect to
trap electrons and then use
the electrons to ionize
propellant, efficiently
accelerate the ions to
produce thrust, and
neutralize the ions in the
plume

Typical Sample Configuration-
Output

Major Specifications
Operating Voltage
Operating Temperature
Range
Hysteresis – The difference between the field
presence/absence to turn on/off respectively.
Magnetic Field Operating Point – The amount
of magnetic flux required to turn on/off the
sensor
Bandwidth

Not passive
Limitations
Must be within certain distance of pole
Very sensitve to EM disturbances
Sometimes sensors retains magnetic field
Not very precise
Has to be mounted very well so tight spaces
and odd positions ussauly make it impossible to
use

Costs
Hall Effect Sensors which measure above 40A
will cost above $30 on average
Sensors which measure below 40A can cost
around $10-$15 on average.
Other types of Hall Effect Sensors
Linear - $5-$10
Switching - $0.40 - $6.00

Digi-Key
Mouser
Honeywell
Where to Buy?
Analog (Usually requires very large order)
Allegromicro.com

Conclusion
Hall Effect Sensor offers a great way to
measure rotation and rotational velocity in a
more precise way than using an optical sensor.
Hall Effect Sensors are a versitle way of
measuring changes in the magnetic field.