Double relay light switching system for providing daytime running lights for vehicles

A double relay control circuit for connection between the ignition switch and starter switch of a vehicle and the vehicle power supply and exterior lights for providing automatic daytime running lights whenever the vehicle ignition switch is ON and the starter switch is OFF and subject to being overridden by the conventional light switches and ambient condition and vehicle condition sensors.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is generally directed to automatic circuits for providing 
automatic daytime running lights (DRL) for automotive vehicles and, more 
particularly, to a double relay switch system for providing DRL whenever a 
vehicle ignition switch is ON and a starter switch is OFF and dependent 
upon the condition of manual overrides, ambient condition sensors and 
vehicle condition sensors. 
2. History of the Related Art 
Automatic headlight and daytime running light (DRL) systems are known for 
use with automotive vehicles. Such systems are designed to provide 
illumination of vehicle headlights and, in some cases, parking or 
taillights and ICC trailer running lights for purposes of improving the 
manner in which a vehicle is made conspicuous in the daytime to thereby 
increase safety. Some existing systems provide for energizing the high 
beam filaments of the vehicle headlights at reduced power and others 
energize the lowbeam filaments of the headlights at normal power. 
In addition to the foregoing, other systems have been designed for further 
controlling the operation of a vehicle exterior lighting system depending 
upon ambient conditions, such as ambient light levels and moisture 
conditions, to ensure that a vehicle's headlights, parking or taillights 
and running lights are fully illuminated in the event ambient conditions 
warrant such illumination during daylight hours. 
Also, to reduce the drain on a vehicle battery, other systems have been 
designed for controlling the illumination of a vehicle exterior lighting 
system depending upon the condition of the vehicle's ignition and starter 
switches. In most such systems, the vehicle circuit includes a manual 
switch for activating the vehicle exterior lighting system with such 
protective circuits only being activated or useful in the event the manual 
switch is in the ON condition. 
Some examples of prior art daytime running light systems are disclosed in 
U.S. Pat. Nos. 4,684,819 to Haag et al., 4,899,083 to Kataoka, 4,686,423 
to Eydt, 4,831,310 to Heintzberger et al., and 4,667,129 to Papillons et 
al. Systems for preventing a drain on a battery system during starting are 
disclosed in U.S. Pat. Nos. 3,764,816 to Johnson, 2,449,338 to Summersett, 
3,993,914 to Conrad et al., 3,348,095 to Gold, 3,385,998 to Gold, 
3,430,100 to Dill, 3,414,763 to Kibler and 4,862,036 to Kriss. 
Systems which are associated with daylight running light systems and which 
incorporate ambient condition light control circuits are disclosed in U.S. 
Pat. No. 4,956,562, 5,136,209, 5,185,558 and 5,614,788, all of which are 
assigned to the same Assignee as the present application. 
SUMMARY OF THE INVENTION 
The present invention is directed to a double relay circuit for providing 
an automatic daytime running light (DRL) system for vehicles which 
includes at least one first or primary normally open relay positioned 
between the vehicle power supply and the vehicle ignition and starter 
switches so as to control power to either the vehicle headlights and/or 
taillights and ICC running lights whenever the ignition is in an ON 
condition and the starter switch is in an OFF condition subject to 
override controls relating to manual switches and ambient condition and 
automotive condition sensors which automatically extinguish the DRL 
circuit. The primary relay has an input connected to the ignition switch 
and is connected to ground through a secondary relay which has an input 
connected to the starter switch, whereby when the starter switch is 
activated, the secondary relay opens to ground and that the primary relay 
switch is also open to ground, thereby preventing operation of the DRL 
system and extinguishing power through the at least one primary relay. In 
some embodiments, a time delay switch may be provided either between the 
vehicle power supply or the ignition switch and the primary relay(s) so 
that the primary relay(s) cannot function until a predetermined time after 
the ignition switch is turned to an ON condition. 
With the present invention, if a conventional light switch is activated, 
the double relay control system is deactivated so that full power may be 
applied through the vehicle dimmer switch to the headlights, parking, tail 
and running lights. Further, the double relay system is disclosed in 
combination with various ambient condition sensors such as moisture 
sensors and light sensors which are operative to override and deactivate 
the double relay control system in the event ambient conditions are 
sensed. Further, the double relay control system is interfaced with 
vehicle condition sensors which monitor such things as the transmission to 
determine if the transmission is in "K" or to sense the position of the 
emergency brake, whereby if the emergency brake is applied or if the 
vehicle transmission is in "K," the double relay control system is 
deactivated to prevent power from being supplied therethrough to the 
exterior lighting system of the vehicle. 
In accordance with one embodiment of the invention, the primary relay 
includes a pair of moveable contacts, each being connected to an output to 
one of either of the vehicle headlights or the vehicle parking, tail or 
ICC running lights. Upon activation of the ignition switch and with the 
starter switch being OFF, power is supplied through the separate contacts 
to the vehicle headlights and the vehicle parking, tail and ICC running 
lights. 
In accordance with another embodiment of the present invention, a pair of 
primary relays are connected between the power supply and the exterior 
vehicle lights with one having an output to the vehicle headlights and the 
other having an output to the vehicle parking, tail and/or ICC running 
lights. The first and second primary relays are interconnected with one 
another to the common ground established by the secondary relay. 
It is the primary purpose of the present invention to provide a double 
relay system for controlling the operation of vehicle headlights and tail, 
parking and running lights to ensure that power is supplied to illuminate 
the lights whenever the vehicle ignition is ON and the starter motor 
actuating switch is OFF. 
It is a further object of the invention to provide a system which may be 
incorporated with a daytime running light system for supplying power to 
the vehicle headlights and other exterior lights and especially reduced 
power to the headlights only or the headlights together with the 
taillights, parking lights and running lights whenever the ignition switch 
is ON and the starter switch is OFF and the manual light switch not 
activated. Under these conditions, lights are illuminated, preferably at 
reduced levels, during daylight hours. 
It is a further object of the present invention to provide a double relay 
control system for providing daytime running lights for vehicles which 
interface with ambient condition sensors and vehicle condition sensors 
which override the double relay control circuit in the event certain 
ambient conditions or certain vehicle conditions are sensed. 
It is a further object of the present invention to provide a relay control 
circuit for providing daytime running lights which may operate 
independently of a conventional vehicle lighting switch, but which can be 
overridden upon the activation of the conventional light switch.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With specific reference to FIG. 1, the double relay control circuits of the 
present invention are designed to supply power to the vehicle headlights 
10, parking, tail or running lights 11, whenever the ignition switch 12 is 
in the ON position and the starter switch is in the OFF position. A first 
or primary normally open relay 15 consists of a movable contact 16 and 
coil 17 . The movable contact is connected to the vehicle 12 volt DC power 
supply or battery "B" through a current overload protector (COP) 18 which 
may be a fuse, thermally activated switch or contacts, or any other 
conventional overload protector. As shown in the circuitry of FIG. 1, when 
the ignition switch 12 is closed to an ON position thereby providing 
current to the coil 17 of relay 15, the movable contact 16 is closed 
thereby supplying current directly to the parking, tail and running lights 
11 and through the vehicle's dimmer switch (DS) 20 to the vehicle 
headlights 10. 
The first or primary relay 15 is connected through a second normally closed 
relay 22 to ground. Therefore, whenever the relay 22 is open, power 
through the primary relay is automatically terminated. Relay 22 includes a 
normally closed movable contact 23 which is urged into an open position 
upon activation of a related relay coil 24 which receives power through 
the starter switch 13 when the starter switch is in a closed position to 
activate the starter motor. Thus, whenever the starter motor is being 
activated, power to the vehicle headlights and parking or taillights is 
automatically terminated by opening the ground contact to the primary 
relay 15. The double relay, therefore, prevents excess drain on the 
vehicle battery power supply by assuring that power to the lighting system 
is not supplied during the starting procedure. 
An optional normally closed manual by-pass or cut-off switch 25 may be 
included and placed between the ignition switch and the coil 17 of the 
first relay 15 to manually turn OFF the lights. This feature is particular 
advantageous for military uses or utility uses when the engine must be 
operated without the lights being on. Therefore, by opening the manual 
switch 25, even though the ignition switch is ON, the lighting system is 
de-energized. 
With reference to FIGS. 2 and 3, modifications to the primary circuit of 
FIG. 1 are shown. In these embodiments, a time delay ON/OFF switch 26 is 
provided between the current overload protector and the movable contact of 
the first relay 15. The time delay ON/OFF is designed to maintain the 
lights OFF until the engine is running. The time delay switch can be 
placed between the power supply and the lights, as is shown in FIG. 2, or 
may be placed between the ignition switch 12 and the coil 17 of the first 
relay, as is shown in FIG. 3. In actual practice, the time delay switch 
can be placed anywhere in the first relay coil circuit. The time delay can 
also control the OFF time after the ignition switch is de-activated so 
that power is only supplied to the exterior vehicle lights for a 
predetermined period after the ignition is OFF. 
With particular reference to FIG. 4, a modification of the circuitry of 
FIGS. 1-3 is disclosed wherein separate primary relays are provided for 
controlling the operation of the headlights 10 and tail, parking or 
running lights 11. In this embodiment, the first primary relay 15 of FIG. 
1 has been replaced by a pair of relays 15A and 15B each of which is 
normally open and includes a movable contact 16A, 16B which is activated 
by a coil 17A, 17B. Both of the movable contacts 16A and 16B are connected 
through the current overload protector 18 to the vehicle power supply and 
movable contact 16A is also connected through the vehicle dimmer switch 20 
to the vehicle headlights 10. The movable contact 16B is connected 
directly to the vehicle parking, tail or running lights 11. Coils 17A and 
17B are connected to the ignition switch 12 through an optional manual 
override switch 25 so that coil 17A and 17B are activated whenever the 
ignition switch is ON and the manual switched is closed. Both of the coils 
17A and 17B are connected to ground through a normally closed movable 
contact 23 of relay 22. Secondary relay 22 also includes an activation 
coil 24 connected to the vehicles starter switch 13. Therefore, whenever 
the starter switch is in a closed or ON position to activate the starter 
motor, power to the coils 17A and 17B will be terminated as the movable 
contact 23 will be open thereby disconnecting the coils 17A and 17B from 
ground and terminating power to the headlights and other exterior lights. 
The same time delays disclosed in FIGS. 2 and 3 may also be utilized with 
the circuitry of FIG. 4. 
A further embodiment to the control circuitry of FIG. 1 is shown in FIG. 5 
wherein the primary relay 15 has been replaced by a double pole relay 
switch 15C including interconnected movable contacts 16C and 16C' which 
are simultaneously activated by coil 17C which is connected to the vehicle 
ignition switch 12 through an optional normally closed manual override 
switch 25. Movable contact 16C is connected through the vehicle dimmer 
switch 20 to the headlights 10 whereas movable contact 16C' is connected 
directly to the vehicle taillights, parking lights and clearance or 
running lights 11. The movable contacts 16C and 16C' are connected through 
a current overload protector 18 to the vehicle power supply and may be 
connected through a time delay 26, as previously described. Relay coil 17C 
is connected to ground through the normally closed movable contact 23 of 
the secondary relay 22. Coil 24 is connected to the vehicle starter switch 
13 so that whenever the starter switch is activated the normally closed 
contact 23 will be open thereby extinguishing power to the coil 17C of 
relay 15C and extinguishing power to the vehicle lights 10 and 11. The 
time delay 26 may optionally be placed in the circuit between the ignition 
switch and the coil 17C. 
In FIG. 6, the double relay control system of the present invention is 
shown in a circuit to supply power at a reduced level to the high beam 
filaments 10' whenever the ignition switch 12 is ON and the starter switch 
13 is OFF or open. In such a system, it is necessary to be able to 
override the daytime running light (DRL) operation whenever the 
conventional vehicle light switch 14 is activated to provide full power to 
the vehicle headlights and taillights. Power at a reduced level is applied 
in the DRL circuit to the high beam filaments 10' by connecting the 
filaments to the vehicle power supply through a primary relay 15. Movable 
contact 16 which is normally open is connected through a current overload 
protector 18 to the vehicle power supply and is also connected through a 
Zener diode Z1 to the high beam filament 10'. The Zener diode functions to 
reduce the power to an appropriate level so as to illuminate the high beam 
filaments at a reduced level and thereby prolong the life of the high beam 
filament. Movable contact 16 of relay 15 is closed by activation of coil 
17 which is connected to the vehicle ignition switch 12. An optional 
manual override switch 25 and time delay switch 26 may be provided as 
previously discussed to further control power through the primary relay 
15. Coil 17 is connected to ground through normally closed contact 23 of 
relay 22. Normally closed contact 23 is open by activation of coil 24 
whenever the vehicle starter switch 13 is activated to provide power to 
the starter motor. This automatically ensures that all power to the 
vehicle headlights and taillights is terminated at relay 15 whenever the 
starter motor is engaged. Relay 15 is further connected through the 
vehicle dimmer switch 20 to the low beam filaments 10" and may optionally 
be connected to activate the vehicle parking, tail or running lights 11, 
as shown in dotted line in FIG. 6, wherever the coil 17 is activated. 
It should be noted that as opposed to powering the high beam filaments 10' 
of the vehicle headlights at reduced power, the low beam filaments may be 
powered at either a reduced power level or full power level. The relays 
would function in the same manner as described for regulating power to the 
high beam filaments in a DRL mode. 
The conventional vehicle light switch 14 is connected directly to the 
vehicle parking, tail or running lights 11 and through a diode D3 to the 
vehicle dimmer switch 20 and from there to the vehicle headlights 10' and 
10". It is necessary to override the DRL power supply to the high beam 
filament 10', or power to the low beam filament, in a DRL mode, in the 
event the conventional light switch 14 is activated. To accomplish this, 
whenever the manual light switch is ON, voltage is applied to the coil 24 
of relay 22 opening the movable contact 23 to thereby terminate power to 
the coil 17 of relay 15. By de-energizing the coil 17 of relay 15, the 
relay is open thereby turning OFF the high beam headlights at reduced 
power through Zener diode Z1. Under this condition, optional or 
alternative power to the tail, parking and running lights, and/or the low 
beam headlight filaments, as shown in dotted line in FIG. 6, is also 
extinguished through relay 15 and power is applied directly through the 
vehicle light switch 14 to the exterior vehicle lights including 
headlights and taillights. A diode D1 is placed between the starter switch 
13 and the junction of the circuit from the light switch 14 to the coil 24 
of relay 22 so that the light switch activation does not activate the 
starter. Diode D2 is placed between the light switch circuit and the 
junction of the light switch circuit to the starter motor switch 13 so 
that when the starter switch is activated the normal manual light switch 
is not activated. The diode D3 is placed ahead of the input side of the 
dimmer switch 20 to prevent back feed voltage from the high beam 
headlights, during the DRL operation, into the light switch circuit to 
thus preventing the high beam DRL activation from activating relay 22 and 
causing the lights to flash ON and OFF. 
As previously discussed, the time delay 26 may be placed in the circuit 
between the ignition switch 12 and the coil 17 of relay 15 to delay the 
activation of relay 15 until the starter switch is activated. This will 
prevent the lights from coming ON until after the starter switch has been 
released. The manual override switch 25 may be placed between the ignition 
switch 12 and the coil 17 of relay 15 to manually extinguish power to the 
lights at a time when it is necessary to allow continued vehicle operation 
without lights. It should be noted that the relay configurations shown in 
FIGS. 4 and 5 may also be used. 
With reference to FIG. 7, the double relay control circuitry of the present 
invention is shown in further combination with sensors for controlling the 
activation of the exterior vehicle lights including headlights and 
taillights depending upon various ambient conditions, such as the presence 
of moisture or the reduction of light levels. In this embodiment, the 
control of the headlights during the DRL operation of the system is the 
same as described with respect to FIGS. 6 with the optional control of the 
taillights in the DRL mode being shown in dotted line in the drawing 
figure. Again, the double relay configurations of FIGS. 4 and 5 may also 
be used. 
A power take off circuit line 30 is connected between the current overload 
protector 18 and the input to the movable contact 16 of relay 15. Line 30 
is connected to a light sensor (LS) 31 and a moisture sensor (MS) 32 the 
outputs of which are connected to a coil 33 of a third relay 35. Relay 35 
includes a normally open movable contact 36 which is moved to a closed 
position upon the activation of either the light sensor 31 or moisture 
sensor 32 determining a low light level or the presence of moisture. When 
one of the sensors is activated, coil 33 is activated thereby closing the 
contact 36 and providing power from the power supply directly to the 
vehicle parking lights, taillights and running lights 11 and to the 
vehicle headlights 10' and 10" through diode D3 and the dimmer switch 20. 
The output of switch 35 is also shown as being connected through diode D2 
to the coil 24 of relay 22. Therefore, whenever the power is being 
supplied to the dimmer switch 20 and to the parking, tail or running 
lights 11 by activation of the relay 35, relay 22 will be caused to open 
thereby terminating power to coil 17 of relay 15 and thus de-activating 
the power supply through Zener diode Z1 in the DRL mode to the vehicle 
headlights and optional parking lights 11. 
As opposed to monitoring moisture by way of a moisture sensor (MS) 32, or 
in addition thereto, a separate automotive condition sensor may be 
provided for monitoring activation of the vehicle windshield wiper circuit 
40 (WW), as shown in dotted line in FIG. 7. Whenever the windshield wiper 
motor(s) is activated, power will be supplied to coil 33 of relay 35 
thereby closing contact 36 and extinguishing the DRL mode of light power 
supply. 
The relay control circuit of the present invention may also be utilized in 
combination with control sensors for monitoring other specific conditions 
of the vehicle so that power in the DRL mode is prevented even when the 
ignition switch 12 is ON and the starter motor switch 13 is OFF. In some 
instances, automatic illumination of the vehicle exterior lights may not 
be desired, such as when the vehicle is parked or when the emergency brake 
is applied. A sensor (TP) 42 may be associated with the vehicle 
transmission which is operable to supply current to coil 23 of relay 35 
when the transmission is placed in "K." A sensed position of the 
transmission lever or control will therefore override the DRL operation of 
the lighting system. Likewise, a sensor (PB) 45 may be incorporated with 
the vehicle parking brake to provide power to the coil 33 of relay 35 
whenever the parking brake is engaged to thereby override the DRL 
operation of the lighting system. 
The following truth table shows the possible operative combinations of the 
relay control circuit of the present invention when incorporated with the 
DRL, ambient condition sensor (ACS) and vehicle condition sensors (VCS). 
The number "1" indicating an ON condition and "0" an OFF condition. 
A Truth Table, Table I, of the embodiment shown in FIG. 7 of the 
inputs--ignition switch 12, starter switch 13, light switch 14, any one or 
both ambient condition sensors (ACS) 31, 32, and any one or more vehicle 
condition sensors (VCS) 40, 42, 45--and outputs --DRL (HB only, LB only, 
HB and PL, HB and PL) HL, and PL (normal through the conventional 
headlight switch)--of the present invention. 
TABLE I 
__________________________________________________________________________ 
8 INPUTS 3 OUTPUTS 
__________________________________________________________________________ 
IGN (12) 
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 
ST (13) 
1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 
LS (14) 
0 0 1 1 1 1 0 0 0 1 1 1 1 0 0 0 
ALS 0 0 0 1 1 0 1 1 0 0 1 1 0 1 1 0 
VCS 0 0 0 0 1 1 1 0 1 0 0 1 1 1 0 1 
DRL 0 1* 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
HL 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 
PL 0 0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 
__________________________________________________________________________ 
*Note: DRL will go to "0" if auxiliary manual cutoff switch 25 is open 
between the ignition switch and the relay control circuit. 
The foregoing description of the preferred embodiment of the invention has 
been presented to illustrate the principles of the invention and not to 
limit the invention to the particular embodiment illustrated. It is 
intended that the scope of the invention be defined by all of the 
embodiments encompassed within the following claims and their equivalents.