UPDATE : 2017-09-07
devices are extensively applied to modern automobiles, including signal sensors on
distributors, speed sensors in ABS systems, autometers and odometers, liquid
physical quantity detectors, current detection and working status diagnosis
sensors for various electric loads, engine speed sensors and crankshaft angle
sensors, various switches, etc.
Here, automobile ignition
system is taken as an example. The designer uses a Hall sensor to replace the
traditional circuit breaker used in the distributor as the ignition impulse
generator. The kind of Hall ignition impulse generator will produce impulse
voltage inside the electriferous semiconductor along with the magnetic field
with varying speed to control primary current of electronic control unit (ECU).
Compared with the traditional mechanical circuit breaker, the Hall ignition
impulse generator has no wear and is maintenance-free, which can fit harsh
working environment. Besides, it can accurately control ignition timing and
substantially improve engine mobility, featuring distinct advantages.
Hall power circuit used on
the automobile switching circuit is able to restrain electromagnetic
interference. It’s known to all that the higher the automation degree of an
automobile, the more microcircuits used on it, and the more it is vulnerable to
electromagnetic interference. However, many lamps and electric devices used on
the automobile, headlamps, A/C motor and wiper motor featuring large power in
particular, can produce surge current at the moment they are powered on or off.
Mechanical switching contacts will generate arc and produce large
electromagnetic interference signals in this case, while use of Hall power
switching circuit can reduce the effect.
Hall devices detect changes
in the magnetic field and convert the changes to electric signals before
output, which can be used to monitor and measure changes in operating
parameters of automobile parts, for instance, position, displacement, angle,
angular speed and revolving speed. They can make secondary transformation of
these variables and measure others like pressure, mass, liquid level, flow
velocity and flow as well. Output quantities of Hall devices are directly
accessed to ECU to realize automatic detection.
Currently, Hall devices can
all bear certain vibration and are able to work in the temperature range from
are completely sealed to be free from water and oil contamination and can be
totally fit for harsh working environment of automobiles.
Recommended Hall sensors:
LC2441F, LC2422 and LC2421
Recommended magnets: bonded
NdFeB, sintered NdFeB, and samarium cobalt