Transcript Lighting - Totton College

Lighting
The Basic Bulb
Filament
Bulb uses electrical current to
produce light.
Glass
Filament held in position by
supports.
One support connects to
centre contact.
Support 1
Support 2
One support connects to cap.
Cap
Air removed to reduce heat loss,
oxidation and vaporization.
Centre contact
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The Basic Bulb
Filament
Filament is heated by current flow
and produces light.
Glass
Emits white light when
heated to 2300°C.
Bulb produces less light when
supply voltage is below bulb
rating.
Support 1
Bulb produces more light when
supply voltage is above bulb rating,
until filament burns away.
Support 2
Cap
Centre contact
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Quartz Halogen bulbs.
• They are used in headlights and consist of a quartz
envelope which is filled with a special gas of
halogen additives such as iodine or bromine. Quartz
used instead of glass, due to its greater strength
and high temperature a property which allows the
filament to be heated too much higher
temperatures.
Bulb Types
Quartz halogen type.
Used in headlights, spot,
driving and fog lights.
Voltage
terminals
Halogen
bulb
Metal
flange
with lugs
Quartz
Quartz used instead of glass,
due to strength and high
temperature properties.
End
shield
Interior is pressurized to reduce
burning away of filaments.
Shields allow bulb to produce
required beam patterns.
Lugs on metal flange ensure
bulb is fitted correctly.
Main
filament
Dip
filament
Shield
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Handling
• State why you must not touch the glass on
halogen bulbs, when handling them.
• The salt from your sweat will stain the quartz
and shorten the bulbs life.
• Describe how you should you clean the bulb if
you do touch it.
• Wipe clean with methylated sprit whilst cold
and allow drying before using.
Identify the markings of these
automotive bulbs.
•
•
•
•
Manufacturers name
Voltage and wattage
Configuration type
U = UV emission below
EU limit
• International regulation
• EU approval
• Test number
Bulb Types
Small bayonet cap,
single contact type.
Used in side, rear, license plate,
fog and indicator lights.
Small bayonet cap,
twin contact type.
Used in combined brake
and rear lamps.
Xenon HID bulbs, used
in headlights.
Produce more light than halogen
bulbs and use less power.
Next >
A Basic Headlight
Parabolic reflector
Contains a bulb, a parabolic
reflector and a lens.
Lens
Bulb
May be fitted with a
shield to cut-off light.
Voltage terminals at rear.
Voltage
terminals
Headlight is weatherproof.
Shield
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Basic Headlight Beam Patterns
Parabolic
Shape of reflector
determines beam pattern. reflector
Parallel beam
produced by
positioning filament at
focal point.
Parallel beam
Ideal design for
spot lights.
Bulb
Filament at focal
point
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Basic Headlight Beam Patterns
Dip beam produced by
positioning filament above
focal point.
Parabolic
reflector
Filament above
focal point
Side beam produced by
positioning filament to
one side of reflector.
Dip
beam
Bulb
Next >
Basic Headlight Beam Patterns
Some bulbs are fitted
with shields.
Concentrated
dip beam
A shield under a filament
concentrates the beam
pattern upward.
Shield
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Free Form Headlights
Reflector
segments
Reflectors are designed to
tight tolerances.
Front
view
Surface focuses and
scatters light beams.
Reflector
Divided into segments
to illuminate segments
of road.
All of the surface area is
used to provide a beam
pattern.
Lens is a clear cover, with
no optical pattern.
Side
view
Dip beam
pattern
Shield
Filament
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Projection Headlights
Projection headlight
Small in
diameter, but
produce high
output.
An ellipsoidal
reflector reflects light
onto a lens.
Ellipsoidal
reflector
Beam
pattern
Lens
The lens projects
light in the required
pattern.
Shield cuts-off
unwanted light.
Filament
Shield
Next >
Xenon bulbs
Xenon bulbs do not use a filament. Instead,
they produce light when a high voltage is
passed between two tungsten electrodes
through a mixture of xenon (an inert gas) and
certain other metal halides. In addition to
strong lighting power, electronic control of the
power supply gives the headlamps stable
quality and tone colour.
The following are some advantages of
the xenon type headlamp.
• The light produced by the headlamps is white in
colour similar to sunlight
• Light output is nearly double that of halogen
headlamps, affording increased area of
illumination.
• Reflected luminance is increased which enhances
contrast on wet roads
• Power consumption is approximately 25 percent
less than halogen headlamps, reducing battery
load.
Xenon bulb operation
• However, the voltage required to initiate the arc
between the two capsule electrodes of a HID
lamp is approximately 25,000 V and a current
flow of approximately 20 A is required. Once the
arc is initiated, the voltage requirement reduces
to approximately 75-80 V with a reduced current
flow of only 3.5 A. To initiate and maintain the
electric arc within the xenon capsule, an
electronic control unit incorporating an electronic
ballast unit produces the required voltage by
effectively converting the original 12 V supply.
Safety note
• Note: To prevent personal injury due to the
high voltages and current levels created in a
HID system, the technician should always
ensure that all the necessary safety
precautions, as detailed by the manufacturer,
are taken into account before working on the
system.