SS4/SS5/SS400/SS500 Low Gauss Bipolar Hall
Effect Sensors
Industry: Manufacturing
Application Note
Application: Brushless DC Motor
INTRODUCTION
This application note discusses the use of the
Honeywell SS4/SS5/SS400/SS500 Series Hall effect
sensors in place of mechanical commutation used in
conventional DC motors.
Brushless DC motor (BDCM) technology, coupled
with Honeywell’s SS Series Hall effect sensors,
provides a cost-effective alternative to conventional
DC motor commutation. When they are used in
brushless DC motor applications cost savings can be
realized in several areas. Honeywell Hall effect
sensors are relatively low-cost devices. The low
operate and release gauss levels required to operate
the Honeywell sensors at 25 °C ±40 °C allow lower
cost commutation magnetics to be used. Because the
sensors are solid state devices they have no moving
parts to wear out. This helps to eliminate
maintenance and performance problems that can be
created by brush wear and the associated brush dust.
Manufacturing and operating cost savings, coupled
with low cost power semiconductors, have made
brushless DC Motors a very cost-effective alternative
in the motor industry.
THEORY OF OPERATION
Brushless DC motors are essentially brush-type
motors turned inside out. Power is fed directly to the
armature windings while a permanent magnet rotor is
the rotating member. This can be either an inner or
outer rotating member, depending on the motor
design. Also, the brushes and commutator of a DC
motor are replaced by position sensors and electronic
switching.
Torque, the force that produces motion, is
developed in DC motors by the permanent magnet
field interacting with the current flowing through the
windings. In brush-type motors, the commutator
switches the armature windings in order to provide
proper magnetic flux and armature current interaction.
In brushless motors, a Hall effect position sensor
senses the position of the rotating magnet and excites
the proper windings through logic and driver circuitry.
Sensing and Control
TYPICAL DRIVE CIRCUITRY
There are many types of DC brushless motor
designs being used today. An 8-pole motor with a 3phase winding is shown in Figure 1. Bipolar or
latching Hall effect position sensors can be used.
Figure 1: Essential Elements of a Typical
Brushless DC Motor
The rotating permanent magnet moving across the
front of the sensor causes it to change state. When
each south pole passes the sensor, the sensor
operates. Figure 2 shows the output of three sensors
placed 30 electrical degrees apart in the DC
brushless motor. In an 8-pole magnet brushless
motor, each south pole is 90 degrees from the next
pole. When three sensors are placed 30 degrees
apart, the first sensor will operate at 30, the second at
60 and the third at 90 degrees.
Figure 2: Sensor Operation
Bipolar Hall Effect Sensors
When the north pole passes the sensors, they will
release. Each north pole of the rotating 8-pole magnet
is 45 degrees from the adjacent south pole. Each
sensor will release at 45 degrees after operating.
The three sensor outputs are used as shaft position
encoders. The sensor signals magnet position and
polarity information to a logic circuit which switches
on power transistors arranged in an “H” bridge
formation.
Figure 3 is an example of driver circuit using six
power transistors and three Hall effect sensors.
Figure 3: Driver Circuit for Three Phase BDCM
Each pair of power transistors are correspondingly
activated and deactivated based on the position of
the rotating magnets. Based on magnet position
current to the armature windings is provided in the
appropriate sequence and time. The sensors can be
placed at the end of a motor’s shaft, directly inside the
motor, or around a ring magnet attached to the rotor
shaft. Figure 4 illustrates the three methods.
SS4/SS5/SS400/SS500 SENSORS
SS4/SS5/SS400/SS500 Series Hall effect sensors
provide the precise motor shaft positioning data
needed by brushless DC motors. These sensor series
include magnetically bipolar sensors which have
positive operate and negative release points that are
nearly magnetically symmetrical over temperature
range. A sensor operating at positive 90 gauss will
release at negative 90 gauss.
Series
Temperatature Range
SS4
SS5
SS400
SS500
-55 °C to 150 °C [-67 °F to 302 °F]
-40 °C to 150 °C [-40 °F to 302 °F]
-40 °C to 150 °C [-40 °F to 302 °F]
-40 °C to 150 °C [-40 °F to 302 °F]
Operating
Voltage
4.5 Vdc to
24.0 Vdc
3.8 Vdc to
24.0 Vdc
SS4/SS400 Series digital sensors have 14.99 mm
[.590 in] printed circuit board terminals on 12.7 mm
[.500] in mounting centers. SS400 sensors are
available on tape and reel with formed leads on
2.54 mm [.100 in] centers.
SS5/SS500 Series sensors are supplied in industry
standard SOT89 gull wing surface mount package,
compatible with pick-and-place equipment for
automated assembly operations.
For electrical and magnetic characteristics,
mounting dimensions, operate and release points visit
the Honeywell Web site or contact your local Sensing
and Control representative.
Figure 4: Typical Sensor Locations
RPM and direction sensing are also possible uses
for Hall effect sensors in brushless DC motors.
Additional Hall effect sensors can be used to
accomplish these functions. An example of this would
be Honeywell’s dual Hall effect sensor SS526DT. The
SS526DT sensors incorporate two digital Hall effect
sensors that can be used to provide both speed and
direction output information.
2 Honeywell · Sensing and Control
www.honeywell.com/sensing
Bipolar Hall Effect Sensors
WARRANTY/REMEDY
Honeywell warrants goods of its manufacture as
being free of defective materials and faulty
workmanship. Contact your local sales office for
warranty information. If warranted goods are returned
to Honeywell during the period of coverage,
Honeywell will repair or replace without charge those
items it finds defective. The foregoing is Buyer’s sole
remedy and is in lieu of all other warranties,
expressed or implied, including those of
merchantability and fitness for a particular
purpose.
Specifications may change without notice. The
information we supply is believed to be accurate and
reliable as of this printing. However, we assume no
responsibility for its use.
While we provide application assistance personally,
through our literature and the Honeywell Web site, it
is up to the customer to determine the suitability of
the product in the application.
For application assistance, current specifications, or
name of the nearest Authorized Distributor, check the
Honeywell Web site or call:
1-800-537-6945 USA
1-800-737-3360 Canada
1-815-235-6847 International
FAX
1-815-235-6545 USA
INTERNET
www.honeywell.com/sensing
info.sc@honeywell.com
Sensing and Control
Honeywell
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Freeport, Illinois 61032
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