Abstract:
Brake controllers typically require a microprocessor or some complex digital circuitry to achieve a proportional brake control signal suitable to control electric brakes on a towed vehicle. These components can be difficult to manufacture and can be expensive. Therefore, a brake controller comprises a case, a positioning member held by the case, and an accelerometer attached to the positioning member, wherein the positioning member is moveable to position the accelerometer in an operable position

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from U.S. Provisional Patent Application No. 60/622,434 filed on Oct. 27, 2004, which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to a brake controller, and more specifically, to a brake controller utilizing low cost analog or digital circuitry with a solid-state accelerometer attached to a positioning member.  
       BACKGROUND OF THE INVENTION  
       [0003]     Conventional prior art for brake controllers typically require a microprocessor or some complex digital circuitry to achieve a proportional brake control signal suitable to control electric brakes on a towed vehicle. Such brake controllers often utilize accelerometers mounted to a printed circuit board in a fixed position. Typical brake controllers can use an analog circuit. Such analog brake controllers utilize a pendulum that either breaks a light beam or a pendulum that utilizes a Hall cell and magnet.  
         [0004]     Another alternative is to use a pendulum or a mass movement sensing device for sensing the deceleration of a towing vehicle and for operating either a mechanical or an electrical braking system in the towed vehicle. Examples of such pendulum systems are disclosed in U.S. Pat. Nos. 2,870,876 and 3,053,348. One type of electronic brake controller that includes a pendulum unit for sensing the deceleration of the towing vehicle is disclosed in U.S. Pat. Nos. 3,953,084 and 5,741,048. The pendulum of this patent is provided with a shield to block the passage of light from a light source to a light-sensing unit when the pendulum is in a resting position. When the brakes of the towing vehicle are operated and the vehicle decelerates, the pendulum will swing, permitting light to fall on the light sensing unit that then generates a proportional control signal. The brake controller is responsive to the control signal for producing a pulsed output signal having a fixed frequency and a variable pulse width proportional to the level of the control signal to apply to the brakes of the towed vehicle. However, these systems can have difficulty if the brake controller is not adjusted properly.  
         [0005]     Finally, microprocessor based brake controllers have combined either a single axis or dual axis accelerometer with digital circuitry to automatically adjust the brake output voltage based on mounting angle of the brake controller in the vehicle. These systems can be very expensive and add significant costs to the brake controller.  
       SUMMARY OF THE INVENTION  
       [0006]     An embodiment of the present invention is directed to a brake controller. The brake controller comprises a case, a positioning member held by the case, and an accelerometer attached to the positioning member, wherein the positioning member is moveable to position the accelerometer in an operable position  
         [0007]     According to another embodiment of the present invention a brake controller comprises a clip attachable to a vehicle, a case attachable to the clip, a positioning member attached to the case, a micro-electromechanical system accelerometer or solid state accelerometer attached to the positioning member, and wherein the positioning member is rotatable to position the micro-electromechanical system accelerometer or the solid state accelerometer in an operable position.  
         [0008]     In yet another embodiment of the present invention a method of operating a brake controller is disclosed. The brake controller comprises a case, a positioning member attached to the case, and an accelerometer attached to the positioning member. The method comprises attaching said case to a vehicle, and positioning the accelerometer to an operable position using the positioning member. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]     Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:  
         [0010]      FIG. 1  is a brake controller of an embodiment of the present invention attached to a clip;  
         [0011]      FIG. 2  are a variety of views of the brake controller of an embodiment of the present invention with the clip thereon;  
         [0012]      FIG. 3  are a variety of views of the clip of an embodiment of the present invention;  
         [0013]      FIG. 4  are a variety of views of an embodiment of the printed circuit board holder and the positioning member and pointer in a single molded component;  
         [0014]      FIG. 5  is an exemplary electrical schematic diagram of the electronic system of the brake controller according to an embodiment of the present invention;  
         [0015]      FIG. 6  is block diagram of the function of the brake controller of an embodiment of the present invention; and  
         [0016]      FIG. 7  is a simplified block diagram of the function of the brake controller of an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]     The present invention utilizes a low cost micro-electromechanical system (“MEMS”) or solid-state accelerometer (e.g., Memsic MXR2999ML) to generate a proportional voltage applied to a towed vehicle&#39;s brakes based on the vehicle&#39;s deceleration rate. Other single or dual axis accelerometers, Motorola MMA2260D2, Analog Devices ADXL105, ADXL213, or other accelerometers may be used. Further, the present invention utilizes a positioning member and indicator device to properly adjust the accelerometer signal to compensate for various mounting angles of the brake controller. The proper position of the internal accelerometer sensor is a horizontal plane. The operator, by manually positioning the indicator device, such as a pointer to the down direction, accomplishes this initial condition. Fine-tuning may require the operator to adjust the positioning member to provide for either an aggressive or delayed response from the brake controller.  
         [0018]     The brake controller of the present invention further utilizes a brake control-plastic mounting clip with adjustable mounting positions. The clip incorporates a plastic clip portion that when attached to a vehicle&#39;s mounting surface, it allows the operator to make slight mounting angle adjustments without tools so as to allow the operator to better view the display of the brake controller. Prior art mounted brake controllers either required tools for adjustments, or were not capable of multiple angle positions. Ease of use, combined with a styled and color matched appearance creates a uniform appearance of the brake control and the mounting means.  
         [0019]     With reference to  FIG. 1 , a brake controller  10  for controlling the brakes of a towed vehicle of the present invention is shown. The brake controller  10  comprises a case  12 , such as a plastic case. The case  12 , however, can be made from just about any material, such as plastic, rubber, metal (e.g., aluminum), or a combination of such materials.  
         [0020]     The brake controller  10  is installed on a clip  15  for ease of installation into the cab of a vehicle (not shown), and in particular, onto a vehicle&#39;s mounting surface. The clip  15  of the present embodiment includes rear supports  20 , front legs  25 , and mounting slots  30  as shown in  FIGS. 1 through 3 . It should be understood, however, that this is an exemplary embodiment and the clip  15  may take alternative embodiments and configurations. For example, the clip may be metal and may require screws to be attached to the vehicle&#39;s mounting surface. The brake controller  10  may be removably attached to the clip  15  so that it may be easily removed therefrom. Alternatively, the brake controller may be permanently fixed to the vehicle&#39;s mounting surface.  
         [0021]     To attach the brake controller  10  to the clip  15 , the brake controller  10  is placed into the rear supports  20  and is then angled into position using the front legs  25  and the mounting slots  30  on the side of the clip  15 . When installed, the brake controller  10  will fit securely into the clip  15  as shown in  FIG. 1 . By moving apart the front legs  25 , the brake controller  10  may easily be removed from the clip  15  for storage. More specifically, the clip  15  allows the brake controller  10  to be a quick disconnect clip. No tools will be needed to remove the brake controller  10  from the clip  15 . An operator can use his or her hands to easily and quickly remove the brake controller  10 . This allows the brake controller  10  to easily be removed from the vehicle when it is not needed. Additionally, the clip  15  can be removed from the mounting surface when the brake controller  10  is not in use.  
         [0022]     Further, the clip  15  allows the brake controller  10  to be manually adjusted in several positions relative to the mounting surface of the vehicle. In the present embodiment, the clip  15  allows for at least three adjustable positions. However, any number of adjustable positions can be used. Adjusting the position of the brake controller  10  using the clips  15  permits the brake controller  10  to adjusted so that a display  22  of the brake controller  10  is easily visible to the operator based on its mounting angle.  
         [0023]     When the clip  15  is mounted onto the vehicle&#39;s mounting surface and the brake controller  10  is mounted thereto, the operator may also need to make an adjustment to the printed circuit board, or more specifically, the accelerometer, based upon the mounting angle of the brake controller  10  so as to position the accelerometer in an operable position. The operator may use the clip  15  to position the brake controller  10  so as to see the display  22 . This, however, may move the accelerometer in the brake controller to an inoperable position. Accordingly, the accelerometer needs to be moved to an operable position.  
         [0024]     The present embodiment utilizes a positioning member  100  to adjust the printed circuit board, and, in particular, the accelerometer and its signal, to compensate for various mounting angles of the case  12  of the brake controller  10 . The positioning member  100 , therefore, adjusts the position of the accelerometer to place it in an operable position irrespective of the position of the brake controller  10 . As shown in  FIG. 4 , the positioning member  100  may be a sensor-positioning arm. Alternatively, the positioning member  100  may also take other configurations not just that shown in the figures, e.g., a cylinder, a rectangular shape, an oval shape, etc. Further, the positioning member  100  includes an indicator device  110 , such as the pointer shown in the figures. Alternatively, the indicator device  100  can take other configurations, e.g., a knob, a display, etc.  
         [0025]     The operator, by manually positioning, such as by rotating, the positioning member  100  until the indicator device  110  is in the down direction, compensates for particular mounting angles of the brake controller  10 . In particular, by the operator manually positioning the positioning member  100 , the accelerometer of the brake controller is manually adjusted into an operable position irrespective of the position of the brake controller  10 . By moving the positioning member  100 , the accelerometer is moved into its operable position. The operator, further, may adjust the positioning member  100  to provide for either an aggressive or delayed response from the brake controller  10  based upon the towed vehicle weight and road surface conditions. The operator accomplishes this similarly as described above. In particular, the operator can rotate the positioning member  100  and can use the indicator device  110  as a visual reference.  
         [0026]     More specifically, when the brake controller  10  is positioned within the cab of the vehicle, it may cause the accelerometer to be placed in an inoperable position. Accordingly, the accelerometer must be positioned to an operable position for the brake controller  10  to operate properly. To accomplish such, the operator will position the positioning member  100  until the accelerometer is in an operable position. For example, the operator can rotate an external portion  120  of the positioning member  100  until the indicator device  110  indicates that the accelerometer is in an operable position. Alternatively, the operator can rotate the positioning member  100  until the brake controller  10  indicates using a display, chime, etc. that the accelerometer is in an operable position. Thus, providing a brake controller  10  with a manually adjustable accelerometer.  
         [0027]     The present embodiment incorporates the printed circuit board support and holder, and the external portion  120  of the positioning member  100  and indicator device  110  in a single molded component, as is shown in  FIG. 4 . The single piece design incorporates a printed circuit board support and holder  125  where both ends serve as a card guide  127  and board support holder  129 . Additional printed circuit board side supports  131  secure the printed circuit board securely from side to side. A bearing surface  133  is also incorporated into the same single molded plastic piece. The opposite bearing support surface piece can be integrated into the side of the case or can be a separate piece. Finally, the single piece incorporates anti-rotation stops  135  to limit the angular travel to be within the desired range to prevent over rotation of the positioning member  100 .  
         [0028]     In order to assemble the brake controller  10 , the accelerometer printed circuit board is placed in the front board slot between the two side alignment pieces. The printed circuit board is then pressed down and snapped into place. The two rear locking latches hold the printed circuit board securely. The positioning member  100  and accelerometer printed circuit board are then pushed into the bearing support that is part of the case  12  side.  
         [0029]     The brake controller  10  further includes an electronic circuit  50 , depicted in  FIG. 5 . The electronic circuit  50  utilizes a micro-electromechanical system (“MEMS”) accelerometer with linear control circuitry. The operator can physically adjust the attitude of the accelerometer to provide aggressive or delayed braking to satisfaction. Additionally, the aggressiveness of the current brake controller  10  will increase when traveling downgrade and decrease when traveling upgrade. Many operators view this as an advantage because it automates what the operator would likely done anyway.  
         [0030]     The current brake controller  10  utilizing the electronic circuit  50 , has two modes of operation, manual and automatic. The manual control is smoother than in prior art brake controllers. In particular, it spreads the application of brakes over most of the range of the potentiometer. The automatic mode has also been made as smooth as possible.  
         [0031]     In an embodiment of the brake controller  10 , it utilizes a current-mode PWM control I.C., U 2 , known as a UC2843/UC3843 High Performance Current Mode PWM Controller made by several manufacturers. The I.C. operates with an internal current-mode loop wrapped by a voltage control loop. This is used with the magnetic load that is presented by the brake magnets. Every pulse initiated by the clock circuit is terminated when the load current reaches the request level. The request level is set by the voltage loop. This technique is automatically short circuit or overload proof.  
         [0032]     As depicted in  FIG. 5 , the UC2843/UC3843 (U 2 ) clock is operated at between 250 Hz and 300 Hz as set by R 6  and C 7  of the electronic circuit  50 . C 7  also sets the minimum off time or maximum duty cycle. Maximum duty cycle is set at about 97%. The inputs to the UC2843/UC3843 (U 2 ) are generated by the manual control and the accelerometer as shown in  FIGS. 6 and 7 . The circuit  50  is set up so that the strongest signal dominates.  
         [0033]     The voltage on the wiper of V 2  moves from 5 volts to about 0.6 volts over the entire stroke. U 4   b  is a buffer to isolate the divider on its output from the “or” circuit on its input. The accelerometer is connected via D 6  to the junction of R 15  and U 4   b,  pin  5 . Both the manual and the accelerometer signal start near 5 volts and go to near 0 volts. D 10  and D 6  match the range of the two inputs and yield the “or” function.  
         [0034]     The error amplifier in the UC2843/UC3843 (U 2 ) is internally referenced to 2.5 volts. To minimize delay at turn on, the input on pin  2  draws a very small amount of current during idle. The ratio of voltage divider (R 8  and R 12 ) is slightly less than 0.5. With the voltage at the junction slightly below 2.5 volts, R 10  will draw a few micro-amps from pin  2 . Since pin  2  is a summing node the output of the internal error amp will be driven upward until the output pulses on pin  6  drive enough current through the gain control circuit (V 1 , D 3 , D 1 , and R 3 ) to offset the current being pulled through R 10 . Because Q 10  is not enabled during idle these very narrow pulses do not reach U 1  and U 6 . They only maintain U 2  at the very edge of turn on.  
         [0035]     As manual control (V 2 ) moves down from 5 volts it drives Q 1  on. Q 1  in turn activates the optional relay (Rly  1 ) via Q 2  and enables the voltmeter via D 8 . Q 1  also drives the gate of Q 4  turning on the accelerometer circuit and enabling the drive from U 2  pin  6  to be connected to the input (pin  2 ) of the high side drivers U 1  and U 6 .  
         [0036]     As V 2  moves down it now provides drive to the error amplifier in U 2  through the aforementioned network between the wiper of V 2  and U 2  pin  2 . Since U 1  is now driven (U 6  is optional for a higher power unit) it delivers pulses from pin  5  to P 1  pin D. These pulses will increase in width until the average current through the gain circuit into U 2  pin  2  equals the current pulled out of pin  2  through R 10 . This current is a function of the duty cycle and the setting of V 1 . The higher the setting of V 1  the higher the duty cycle required to offset the current pulled out by R 10 .  
         [0037]     Returning to the idle mode, a stoplight signal is now applied to P 1  pin B. When this signal exceeds approximately 6.2 volts Q 9  operating in a common base mode will be turned on. The collector of Q 9  will enable the voltmeter and through Q 4  will activate the accelerometer and enable the output coupling of U 2  to U 1 .  
         [0038]     The accelerometer U 3  is mounted on a small printed circuit board such that its active axis is oriented in the direction of travel of the tow vehicle. The accelerometer output voltage is 2.5 volts when it is substantially horizontal. The accelerometer is mounted on a circuit board platform such that the attitude of the accelerometer can be rotated about a horizontal axis transverse to the direction of travel, as previously described. In particular, the accelerometer is mounted on the printed circuit board, which is mounted to the positioning member  100 . The positioning member  100  is positionable such that the accelerometer can be positioned to a substantially horizontal axis transverse to the direction of travel.  
         [0039]     This allows the accelerometer to be “leveled” to accommodate various mounting angles of the brake controller  10 . In particular, if the brake controller  10  is mounted such that the accelerometer is not in an operable positioning, the operator may rotate the positioning member  100 , until the accelerometer is “leveled” and is operable. This also allows the driver to adjust the accelerometer to yield an aggressive or delayed setting. An aggressive setting starts out yielding a brake output of perhaps 1 to 3 volts when the brake pedal is initially pressed. To accomplish this, the operator can rotate the positioning member  100  until the accelerometer is slightly angled (as if the brake controller  10  where going downhill). A delayed setting yields a brake output that requires some actual braking of the tow vehicle before the control begins any output voltage. This is accomplished by moving the angle of the positioning member  100 , or more specifically, the indicator device  110  slightly towards the front of the vehicle or in the direction of travel.  
         [0040]     When activated by Q 4  in response to an input from either the manual or stoplight signal, the output of the accelerometer as used here starts with an output of approximately 2.5 volts when it is substantially horizontal and moves downward 1 volt per G of deceleration. As the normal range of deceleration involved in stopping seldom exceeds 0.5 G corresponding to 0.5 volts it is necessary to apply gain and offset to this signal. The circuitry around U 4   a  provides this functionality and the diode D 6  couples it into the “or” circuit discussed earlier. An RC circuit on the input to U 4   a  provides a single pole of low pass to restrict the frequency response of the circuit.  
         [0041]     As in manual activation the signal is applied to U 4   b  connected as a buffer. Again as the signal moves down, current is drawn from the summing node of the error amplifier in U 2 . The control responds by increasing the pulse width (duty cycle) of the output keeping the output proportional to the accelerometer demand signal. The capacitor C 3  in conjunction with R 10  provides another pole of low pass filtering. The error amplifier is configured as an integrator with open loop gain of about 90 db (about 33000).  
         [0042]     The VN920 high current output driver comprises an N-channel MOSFET and charge pump circuitry to drive the gate of the MOSFET. It also has a built in current mirror with level translator and various protection circuitry to make the device nearly indestructible. The translated current mirror signal is used as the feedback for the UC2843/UC3843 current loop. This signal is generated as a current source at pin  4  of the VN920. R 5  and R 21  convert this signal to a voltage to be used by the UC2843/UC3843 to close the loop.  
         [0043]     Current mode controls such as this have instability when operated at greater than 50% duty cycle. It may, therefore, be necessary to apply slope compensation in proportion to the negative slope of the magnetic circuit. This is the rate of decay of current in the magnets while the output is off. During this time the current is flowing through D 5 . The inductance and resistance of the load in conjunction with the forward drop of the flyback diode D 5  establish the decay rate.  
         [0044]     At high duty cycle the current sense signal gets rather flat and a small amount of noise on the signal can cause the pulse to terminate early or late. It can be shown that such a perturbation will not converge and damp out but will instead grow to the point of skipping entire pulses. This is referred to as sub-harmonic oscillation. The problem is especially difficult because of the wide variation in load. The control is intended to drive 2, 4, or 6 brake magnets. On the other hand, too much compensation defeats the current mode operation and turns the circuit back to a voltage loop.  
         [0045]     An appropriate signal can be added to the current sense signal to cause it to intersect the threshold at a steeper angle. This signal is taken from the saw-tooth oscillator on U 2  pin  4 . An emitter follower (Q 3 ) is used to reduce the load on the oscillator. This signal coupled through R 20  to the signal developed across R 21  provides adequate compensation over all conditions.  
         [0046]     Q 10  and Q 11  perform multiple functions. First they permit gating the drive signal to U 1  and U 6 . Second they provide load dump protection for the VN920. During a load dump the vehicle may be at maximum alternator current output when the connection to the battery opens. Since the regulator does not respond immediately the alternator voltage may rise to 60 or 70 volts for up to 300 ms.  
         [0047]     A simple transfer from ground to Vbatt would have to be very large to withstand this transient and protect the circuitry. Placing a resistor in the ground leg of the VN920 (pin  1 ) and a zener diode from pin  1  to Vbatt prevents excess voltage from being applied to the control portion of the VN920. With 100 ohms in the ground leg (R 39 ) the ground offset is only 0.5 volts while the VN920 is on since the ground current is only 5 ma. Additionally, by grounding the emitter of Q 11  to the top of R 39  the voltage rise on R 39  during a load dump turns off Q 11  and turns on U 1  and U 6 . This reduces the voltage across the embedded MOSFET to about 0.5 volts and delivers the load dump pulse to the brake magnets that can handle the energy with ease.  
         [0048]     More protection is provided by Z 1  and R 2 . Without these components if the connection to ground is accidentally lifted and the control is activated the absence of ground can cause the unit to not operate properly. Initially the control will find ground through D 5  and the load. When the control is activated the flyback during the off time will act as boost type power supply and generate a very high voltage across C 4 . The positive terminal of C 4  will of course stay at Vbatt while the negative terminal will drive negative until some circuit element breaks down.  
         [0049]     With Z 1  and R 2  in the circuit any voltage above about 18.5 volts will cause the control to cut back duty cycle. (The zener at 16 volts and the 2.5 volt summing node voltage add up to 18.5.) Voltage above this level will drive current into the summing node and drive pin  1  of U 2  low. The duty cycle will go to zero until the voltage on C 4  decays. If the situation still exists the pattern will repeat. This will continue until the control is no longer activated or the ground is reconnected. Additionally, Z 3  and R 4  protect U 2  from excessive voltage.  
         [0050]     During load dump the Is terminal of the VN920 is protected from going more than 0.6 volts below pin  1  by D 2 . This results in the difference between the load dump voltage and Z 3  appearing across R 5  and R 21  series combination. R 5  in this case reduces the total dissipation during load dump. The circuit could function without R 5  but the dissipation in R 21  would be excessive during load dump.  
         [0051]     U 5  and the circuitry surrounding U 5  perform a dual function. The primary function is that mentioned previously, e.g., a voltmeter. The RC filter of R 27  and C 15  present an average of the output of the brake controller  10  to the A to D input of U 5 . The software reads this voltage and presents it to the operator via a dual seven-segment display.  
         [0052]     Additionally, the software periodically tests the load on the brake controller  10 . Pin  11  drives current into the output through R 32 . If a magnet load is present the output will not rise significantly and no voltage will be seen on pin  10 . The display will show “.c”. If there is no load the display will show “.”. If a load is present and then is disconnected the display will flash “n.c” for about 15 seconds.  
         [0053]     While the circuit described is an embodiment there are of course many equivalents. The chosen accelerometer is a thermal based device but there are capacitance devices available that would serve the same purpose. In fact there may be devices in development using other technologies. All that is of concern is that the device generates a voltage in proportion to acceleration. The functions of the control chip (UC2843/UC3843 (U 2 )) could be embodied in other control chips or a microprocessor. A single microprocessor could encompass the control function as well as the display and test functions. The VN920 high side switch has many equivalents. An equivalent could even be assembled from discrete parts. Also, while the VN920 utilizes an N-channel MOSFET, a P-channel MOSFET based solution could be used.  
         [0054]     As shown in  FIG. 6 , an embodiment of the brake controller  10  includes a vehicle power and ground  200 , a stop light drive  210 , a power control  220  (gain), a manual control  230 , an accelerometer and op-amp  240 , a voltage conditioning filter and protection  250 , a PWM controller  260 , a stoplight drive relay  270 , output drivers with current sense  280 , a display micro  290 , and display drivers and LED display  295 . As shown in  FIG. 6 , the vehicle power and ground  200  is capable of receiving vehicle power input and vehicle power ground input. Further, the vehicle power and ground  200  is capable of sending signals to the voltage-conditioning filter and protection  250  and the stoplight drive  210 . The stoplight drive  210  is capable of receiving stoplight input signals and signals from the vehicle power and ground  200  and the manual control  230 . The accelerometer and op-amp  240  is capable of receiving PWM controller  260  signals. The PWM controller  260  is capable of receiving signals from the voltage conditioning filter and protection  250 , the power control  220 , the manual control  230 , the accelerometer and op-amp  240 , and the output drivers with current sense  280 . The voltage conditioning filter and protection is capable of receiving signals from the vehicle power and ground  200 . The stoplight drive relay is capable of receiving signals from the stoplight drive  210  and capable of sending a stoplight drive output signal. The output drivers  280  are capable of sending and receiving signals from the PWM controller  260  as well as sending signals to the display micro  290  and the brake output voltage. The display micro  290  is capable of receiving signals from the output drivers with current sense  280  and the PWM controller  260  and sending signals to the display drivers and LED display  295 . The display drivers and LED display  295  is capable of receiving signals from the voltage conditioning filter protection  250  and display micro  290 .  
         [0055]     As shown in  FIG. 7 , an embodiment of the brake controller  10  includes vehicle power and ground voltage conditioning filter and protection  310 , inputs  320 , accelerometer and op-amp buffer  330 , PWM controller  340 , output drivers with current sense  350 , and display  360 . The inputs may include gain control, manual control, and stoplight input. The input  320  is capable of receiving signals from the stoplight input and is capable of sending signals so the PWM controller  340 . The accelerometer and op-amp  330  is capable of sending signals to the PWM controller  340 . The vehicle power and ground voltage conditioning filter and protection  310  is capable of receiving signals relating to vehicle power input and vehicle power ground and is capable of sending signals to the PWM controller  340 . The output drivers with current sense  350  are capable of sending and receiving signals from the PWM controller  340  and are capable of sending signals relating to brake output voltage and stoplight drive. Finally, the display  360  is capable of receiving signals from the output drivers with current sense  350  and the PWM controller  340 .  
         [0056]     Although certain embodiments of the present invention have been illustrated in the accompanying drawings and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the embodiments disclosed, but that the invention described herein is capable of numerous rearrangements, modifications, and substitutions without departing from the scope of the claims hereafter.