Throttle position sensor advanced brake light device

An advanced brake light signalling apparatus utilizes an output from a potentiometric position sensor, buffers the output, differentiates the buffered signal, compares the differentiated signal with a reference, and depending upon the results of the comparison activates the brake lights of a vehicle for a minimum time period. The position of the accelerator at the time of initiation of motion may be utilized to adjust the reference to which the differentiated signal is compared.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to early warning brake lighting systems 
and specifically to a system which utilizes a signal from a throttle 
position sensor. 
2. DESCRIPTION OF THE RELATED ART 
Automobiles have developed through time from the original models which were 
barely able to exceed human walking speed to where relatively enormous 
velocities are attainable and commonplace. Accompanying this development 
of faster cars has been a requirement for better notification of relative 
changes of movement between vehicles to reduce the likelihood of 
collisions therebetween. Perhaps the most basic of these systems is the 
turn signal in which a driver is able to activate a flashing amber light 
to signal to surrounding drivers an intention to make a change in the 
direction the vehicle is taking. 
Additional lighting systems have evolved which are more automatic due to 
the nature of the change being signalled. The present standard brake 
lights are exemplary. In operation a driver will apply pressure to the 
brake pedal and activate some type of switch which in turn energizes tail 
lights on the vehicle. Observance of the tail lights provides a signal to 
all following motorists that the vehicle is braking. 
While the brake light provides warning to following motorists, with 
increasing velocities and greater congestion on the thoroughfares, 
CTS-641, Throttle Position Sensor Advanced Brake Light Device there is not 
always sufficient warning provided to trailing motorists of the braking of 
a leading vehicle. The time required for response by a trailing motorist 
includes reaction time of the leading motorist, travel time by the leading 
motorist's foot from the accelerator pedal to the brake pedal, and 
reaction time of the trailing motorist. In an environment where numerous 
rear-end collisions are occurring daily, including some of extremely 
serious consequence, anything which can be provided to reduce the total 
time for response by the trailing motorist is beneficial. 
Currently, the automotive industry is providing rear window (third) brake 
lights which improve visibility of the light and allow for viewing from a 
trailing car not only to an immediately leading vehicle, but often to a 
second or further leading vehicle. Studies have illustrated a reduction in 
rear-end collisions with the utilization of the third light However, in 
view of the large number of rear-end collisions where time was 
insufficient for braking by a trailing vehicle, clearly there exists a 
need for a product which will increase that warning time. 
Prior art systems to automatically provide more advanced warning of 
deceleration have included accelerometers which sense the acceleration of 
the vehicle and light the brake lights responsive to deceleration. Other 
systems have included switches mounted onto or in the proximity of the 
accelerator pedal and linkage to sense rapid movement of the accelerator 
in a decelerating manner. Some other prior art systems have sensed 
pressure or force applied to the accelerator pedal to detect rapid 
reduction in force, as might be experienced in an emergency movement away 
from the accelerator. 
Each of the prior art systems suffer from disadvantages which are too 
substantial to elicit widespread acceptance of the devices in spite of the 
statistically significant safety enhancement available CTS-641, Throttle 
Position Sensor Advanced Brake Light Device from implementation. The prior 
art accelerometers tend to be sensitive to random road vibration, and in 
some instances, to the incline of the roadway upon which the vehicle is 
traveling. Additionally, the response time gained from the prior art 
accelerometers is questionable, since the vehicle must be already 
decelerating beyond a minimum threshold to activate the device. If this 
threshold is too great, no advance warning is provided since the brakes 
must already be applied to activate the device. If the threshold is too 
low, transmission shifting and road irregularities will activate the 
device. 
Prior art pressure and force sensors offer advanced warning through the 
necessary time required for a lead motorist to release pressure from the 
accelerator and then apply a pressure to the brake pedal sufficient to 
activate the brake light. This is the travel time of the lead motorist's 
foot referred to earlier. However these prior art sensors suffer from 
complications occurring around the accelerator pedal and linkage. Many 
accelerator pedal sizes and shapes are available. Many different methods 
of applying pressure to the accelerator pedal are utilized, varying 
between individual motorists. Finally, many different installation methods 
may be utilized for the sensors. In view of the varying pedal sizes and 
shapes, a manufacturer must make either custom models for each pedal 
resulting in high cost of manufacture, or the manufacturer must design a 
single sensor which is adaptable for custom installation by the end user. 
The concept of a single adaptable sensor is limiting throughout the prior 
art in that the sensor will disrupt the accelerator pedal to motorist 
connection to the significant dissatisfaction of the consumer to whom the 
product is being sold. Additionally, connection between the sensor and the 
brake lights introduces potential problems related to entanglement of the 
sensor with the pedal and linkage, wearing of the parts subjected to 
motion, and difficulty of proper installation in view of the nonCTS-641, 
Throttle Position Sensor Advanced Brake Light Device standard mechanical 
configuration of accelerators and linkages. 
The prior art devices which overcome many of the aforementioned problems 
utilize connection to or within the accelerator linkage. These devices 
create new hazards for the motorists which are potentially more hazardous 
than the original early warning problem. Binding or lock-up of the 
accelerator linkage during operation will potentially take the vehicle out 
of control of the motorist with serious consequence. This can occur due to 
improper installation, mechanical wear, unintentional disruption of the 
device relative to the linkage, loosening with age of mechanical 
fasteners, and other reasons too numerous to mention. 
SUMMARY OF THE INVENTION 
The present invention overcomes the limitations of the prior art by 
utilizing a rate of change electrical detector, in combination with a 
variable resistance, to sense a rapid movement of the accelerator pedal in 
a decelerating manner. The electrical detector includes a differentiator, 
level detector, one-shot and relay/driver. The variable resistance is 
preferred to be the throttle position sensor, but may alternatively be 
comprised by an accelerator position sensor in those applications where 
the automotive maker has provided such a device. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide a device which will warn 
trailing motorists of an emergency-braking condition of a leading vehicle. 
It is a further object of the invention to provide as much response time to 
a trailing motorists as may be reasonably possible CTS-641, Throttle 
Position Sensor Advanced Brake Light Device 
It is further object to provide a device of high reliability design. 
It is further object to provide a device which does not interfere with or 
alter the accelerator linkage in any way. 
It is a further object to provide a device which is insensitive to road 
conditions and vehicular inclination. 
It is a further object to provide a device which is easy to install in a 
reliable manner. 
It is a further object to provide a device which will not produce false 
signals. 
It is a further object to provide a device which does not alter the 
"cockpit" surroundings of a motorist in any way after the device is 
installed. 
It is a further object to provide a limited adjustment so that the device 
may be adapted to conform to the characteristics of an individual motorist 
and individual vehicle. 
It is a further object to provide a device which adds no moving parts to 
vehicles equipped with the device. These and other objects are 
accomplished through the use of the invention and are not intended to be 
limiting to the scope of the invention. The invention may be best 
implemented through the application of the preferred embodiment described 
hereinbelow. CTS-641, Throttle Position Sensor Advanced Brake Light Device

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates the preferred embodiment of the present invention by 
relationships of various functions. Input buffer 201 receives a voltage at 
TPS input 208 representative of the position of the throttle of an 
automobile. Input buffer 201 minimizes electrical loading of the TPS 
source. Additionally, buffer 201 may provide noise and vibration filtering 
to prevent erroneous signals from activating the balance of the circuitry. 
The buffered TPS signal is conducted from buffer 201 to the input of 
differentiator 202 and simultaneously to one input of level detector 204. 
Differentiator 202 generates an output voltage proportional to the rate of 
change of the buffered TPS output from buffer 201. The output voltage from 
differentiator 202 is provided as an input to level detector 204. Level 
detector 204, in addition to receiving input from buffer 201 and 
differentiator 202, receives a reference voltage from sensitivity adjust 
203. 
The relationship between adjust 203, differentiator 202, and detector 204 
will be considered first and then the additional input from buffer 201 
will be considered. 
Level detector 204 receives a voltage from differentiator 202 
representative of the rate of change of position of the throttle. This 
rate of change voltage is compared with the reference voltage CTS-641, 
Throttle Position Sensor Advanced Brake Light Device provided by 
sensitivity adjust 203. When the rate of change voltage is of sufficiently 
large magnitude (representing rapid change in throttle position) and 
proper polarity (representing release of the accelerator) to exceed the 
reference voltage provided by adjust 203, the level detector 204 provides 
an output signal indicative. In turn, one second timer 205 is activated, 
energizing relay driver 206. Relay driver 206 then provides an output 210 
sufficient to activate vehicular brake lights. The circuit is electrically 
powered by automotive battery through input 209 and power supply filtering 
circuit 207. 
As described above, the preferred embodiment is fully operational without 
any operatively direct connection between buffer 201 and level detector 
204. A voltage is received by buffer 201, converted to a signal 
representing rate of change by differentiator 202, compared to a reference 
by level detector 204, and the results of the comparison utilized by timer 
205 and relay driver 206 to activate brake light output 210 when 
appropriate. In an emergency braking situation a motorist will rapidly 
release the accelerator, resulting in rapid change in the position of the 
throttle. When the release of the throttle is rapid enough to be 
representative of an emergency situation, the brake lights are activated. 
False triggering is avoided, since a rapid release of the accelerator pedal 
is nearly always indicative of deceleration, even if not followed by 
braking Maximum warning is provided to trailing motorists since activation 
occurs simultaneous with rapid foot movement and before the driver's foot 
can reach the brake pedal. Slower, more normal movements do not trigger 
the device. 
a typical accelerator linkage incorporates a return spring which provides a 
return force in the direction representative of deceleration. To depress 
the accelerator, a motorist must overcome CTS-641, Throttle Position 
Sensor Advanced Brake Light Device the force of the return spring. From 
physics, the force required to depress the spring increases with 
increasing depression of the accelerator. This increasing spring force 
also contributes to the maximum rate of change of position of the throttle 
position sensor. In other words, when a motorist has the throttle fully 
depressed, relatively large rates of change of position occur without 
corresponding emergency situations. The same rate of change with the 
throttle only partially depressed would likely represent an emergency 
situation. In order to compensate for the varying rates of change 
depending upon the throttle position just prior to release, the throttle 
position buffered output from buffer 201 is provided to level detector 204 
for additional reference. This particular throttle angle compensation 
reduces the sensitivity of the level detector more as the accelerator is 
depressed more. 
FIG. 2 illustrates circuitry of the preferred embodiment. Input buffer 201 
is comprised by op-amp U1A and low pass filter R1-C1. R1-C1 filters out 
electromagnetically induced noise and vibration effects which might 
otherwise trigger the device. The output of U1A is connected to 
differentiator 202, comprising R2-R5, C2, C3, and U1B. The output of U1B 
is applied to the input of level detector 204 where it is filtered by low 
pass filter R6-C5, and then applied to pin 3 of U2A. A comparison voltage 
is applied to pin 2 from sensitivity adjust 203. The comparison voltage is 
generated by potentiometer R9. R7, R8, and C4 are optional, as earlier 
described. They comprise a voltage divider and sample/hold combination. 
The relative ratio between R7 and R8 determines how much throttle angle 
compensation is provided C4 adds sufficient delay in voltage change that 
the differentiator output is compared with the signal which was present 
prior to the change which produced the differentiator output. In other 
words, a constant throttle angle will produce a constant voltage output 
from U1A and an output midway between V.sub.cc and ground from U1B. When 
the throttle CTS-641, Throttle Position Sensor Advanced Brake Light Device 
angle changes, U1B responds very quickly with a voltage swing away from 
midway, either towards ground or towards V.sub.cc. However, the voltage 
impressed upon C4 remains relatively constant at some sensitivity adjusted 
throttle angle compensated level. Therefore, any rapid throttle angle 
change is compared with a voltage reference present just prior to the 
change. 
One second timer 205, illustrated by U3A, R10, C6, and C7 is a standard 
circuit referencable throughout the literature, as is relay driver 205 and 
power supply filtering circuit 207. 
The preferred embodiment of the present invention is fully implementable 
out of view of passengers. Therefore, no distasteful alterations to the 
passenger compartment are required. In operation there should be no 
indication of the presence of the device to the passengers. However, 
trailing vehicles are provided precious extra warning. With electronic 
implementation using few or no moving parts, in the preferred embodiment 
the relay and adjustment potentiometer R9, the reliability of the device 
is excellent. Where sensitivity adjust R9 is not utilized, the entire 
device may be implemented without moving parts through electronic 
switching as is known in the art. The throttle position sensor provides 
all of the necessary information to the device, leaving nothing to get 
tangled in the accelerator linkage. Electrically connected accelerators 
using an accelerator position sensor provide equivalent information for 
operation of the circuitry. Installation involves a very limited number of 
electrical connections all in parallel with existing wiring, resulting in 
a user installable device whereby improper installation does not seriously 
risk the safety of the motorist, as it would with many of the prior art 
devices. Finally, the sensitivity adjust 203 is provided to adapt the 
device to the characteristics of the individual motorist. CTS-641, 
Throttle Position Sensor Advanced Brake Light Device While the foregoing 
is intended to describe what the applicants believe to be the preferred 
embodiment of the present invention, there is no intention to limit the 
breadth or scope of the invention. Rather, the foregoing is provided in 
accordance with what the applicant believes to be the best mode and 
embodiment of the invention. For example, the invention be manufactured 
with a variety of designs and packaging schemes for either oen or 
aftermarket applications. Similarly, the invention would be equally 
applicable to electric cars and to railway vehicles The full scope of the 
invention is set forth hereinbelow in the claims. CTS-641, Throttle 
Position Sensor Advanced Brake Light Device