Headlight
modulators; the Federal Law authorizing them; the technical
details
©
hdlite.htm
24-C
WAIS Document Retrieval[Code of Federal Regulations]
[Title 49, Volume 5]
[Revised as of October 1, 2001]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR571.108]
TITLE 49--TRANSPORTATION
CHAPTER V--NATIONAL HIGHWAY TRAFFIC
SAFETY ADMINISTRATION, DEPARTMENT
OF TRANSPORTATION
PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS--Table of
Contents
Subpart B--Federal Motor Vehicle Safety Standards
Sec. 571.108 Standard No. 108; Lamps, reflective devices, and
associated
equipment.
S7.9.4 Motorcycle headlamp modulation system.
S7.9.4.1 A headlamp on a motorcycle may be wired to modulate
either the upper
beam or the lower beam from its maximum intensity to a lesser
intensity,
provided that:
(a) The rate of modulation shall be 240 <plus-minus> 40 cycles
per minute.
(b) The headlamp shall be operated at maximum power for 50 to 70
percent of
each cycle.
(c) The lowest intensity at any test point shall be not less than
17 percent
of the maximum intensity measured at the same point.
(d) The modulator switch shall be wired in the power lead of the
beam
filament being modulated and not in the ground side of the
circuit.
(e) Means shall be provided so that both the lower beam and upper
beam
remain operable in the event of a modulator failure.
(f) The system shall include a sensor mounted with the axis of
its sensing
element perpendicular to a horizontal plane. Headlamp modulation
shall cease
whenever the level of light emitted by a tungsten filament light
operating at
3000 deg. Kelvin is either less than 270 lux (25 foot-candles) of
direct light
for upward pointing sensors or less than 60 lux (5.6
foot-candles) of reflected
light for downward pointing sensors. The light is measured by a
silicon cell
type light meter that is located at the sensor and pointing in
the same
direction as the sensor. A Kodak Gray Card (Kodak R-27) is placed
at ground
level to simulate the road surface in testing downward pointing
sensors.
(g) When tested in accordance with the test profile shown in
Figure 9, the
voltage drop across the modulator when the lamp is on at all test
conditions for
12 volt systems and 6 volt systems shall not be greater than .45
volt. The
modulator shall meet all the provisions of the standard after
completion of the
test profile shown in Figure 9.
(h) Means shall be provided so that both the lower and upper beam
function
at design voltage when the headlamp control switch is in either
the lower or
upper beam position when the modulator is off.
S7.9.4.2(a) Each motorcycle headlamp modulator not intended as
original
equipment, or its container, shall be labeled with the maximum
wattage, and the
minimum wattage appropriate for its use. Additionally, each such
modulator shall
comply with S7.9.4.1 (a) through (g) when connected to a headlamp
of the maximum
rated power and a headlamp of the minimum rated power, and shall
provide means
so that the modulated beam functions at design voltage when the
modulator is
off.
(b) Instructions, with a diagram, shall be provided for mounting
the light
sensor including location on the motorcycle, distance above the
road surface,
and orientation with respect to the light.