Truck electrical circuit fundamentals Flashcards
what is a constant power circuit
circuits that are connected to the battery terminal of a starter
type 1 circuit breaker
cycle OFF when breaker rating is exceeded . breakers automatically cycle back ON once overload is removed from the system
Type 2 circuit breaker
equipped with a heat producing resistor and a bimetallic strip that responds to heat by moving away from the heat source
where is a type 1 circuit used
headlights
What is the purpose of daytime running lights
enhance the visibility of the truck during the day and poor weather conditions
what is the purpose of the daytime running light terminal block or module .
lowers system voltage by 2 or 3 v so the daytime running lights are visible but will not blind other drivers . this can also be achieved through a series of terminating resistors
when mounting or changing clearance /marker and tail light systems
always refer to government regulations
what Is a rheostat
its a heat creating variable resistor .
what is PWM
it is a digital signal that turns the circuit voltage on or off
how is PWM DUTY cycle measured
as a % value of ON time vs OFF time
is it possible to make some electromechanical flashers operate in LED light circuits
yes by adding a terminating resistor . by balancing the resistance in a system by the number of turn signal lights . if you change the number of lights the resistance value must change as well
on some electromechanical flashers have one extra terminal that is labelled as a pilot terminal . what would this terminal be used for
in most cases the output from the pilot terminal illuminates a turn signal indicator light circuit
how are backup lights controlled
a transmission mounted switch or ECM . they will come on when the driver shifts the vehicle into reverse
in order for the cab interior light circuit to be able to turn OFF what must happen
all door switches must be in a closed position
what is a solenoid
an electromechanical device that turns electrical energy into linear movement
what is a discrete solenoid
it only has two positions fully open or closed
a door latch would use what type of solenoid
a discrete solenoid
what is a proportional solenoid
a solenoid that can move in an infinite number of positions
what is a latching solenoid
is a discrete solenoid that remains fixed at the end of its travel when it is deenergized
why is a high value resistor installed in parallel with a solenoid
to prevent self induced arching when a solenoid is de energized
what is a clamping diode
acts as a one way electrical current check valve
DC motors use magnetism and electricity to produce what
rotary mechanical motion
what component in a DC motor rotates
armature
what is the limiting force of rotational speed of a unloaded DC motor
CEMF counter electromotive force
what is CEMF
its the voltage produced by a DC motor when it is turning
what are the two types of DC motors
permanent magnet DC motors and field wound DC motors
how can you change the direction a PM motor rotates
by changing the polarity of the magnetic field
where are parallel wound dc motors used
where uniform speed and low starting torque are desirable, such as fan blower motor
what are some methods to allow variable speed motors to rotate at various speeds
. variable electrical resistance
. multiple shunt windings
. pulse width modulation
what is important to remember when mounting voltage-reducing resisters
never mount them near any easily melted or combustible material
(CMVSA) stipulates that cruise control systems must have .
three methods of engine speed control disengagement
what is the purpose of battery isolation switches
to prevent parasitic drains while the truck is parked
what is important to remember when installing a battery isolation switch
install fuses in both positive and negative leads to prevent damage to wiring harness
how can you reduce or eliminate interference and static noise
install a series coil (filter choke) or a parallel - connected capacitor to the units power lead - a parallel - connected capacitor can also be used to reduce noise at the source
how do the truck positioning system warn the driver of potential collisions
a forward looking mono pulse radar sensor able to detect fixed and moving objects up to 500ft away
can you turn off the CWS
no . it is always active at vehicle speeds above 24 kph