Keyless entry function expander

An add-on, or after-market, remote-control vehicle security system expander allows auxiliary remote-control functions to be added to previously-installed remote-control systems. Using complementary remote control functions for multiple actuation encoding permits auxiliary function codes to be transmitted without a change of state in the underlying function. Signal validation by coincidence timing and voltage comparison are used to prevent inadvertent local actuation of the auxiliary remote-control functions. Decoding is also limited to a time-window to reduce electrical interference.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is relates to keyless entry vehicle security systems. 
In particular, the present invention relates to expander modules that can 
be added to those systems to increase the operational options available to 
the user. 
2. Background of the Invention 
Remote control vehicle security systems have become a standard, 
factory-installed feature of present day automobiles. The typical 
factory-installed unit has a two or three button remote control that 
provides certain predetermined functions, usually door lock, door unlock, 
and trunk release. An owner who wishes to add remote starting or window 
control options must replace the factory-installed unit with an 
after-market unit that includes those extra options with the basic three 
provided by the factory installed unit. Thus the consumer is stuck with 
the cost of a second installation, as well as a product that duplicates 
the functions of the factory-installed unit that must be replaced. 
Some after-market units are available that add as many as two additional 
functions to the basic, factory-installed three-function units. However, 
the units presently available merely piggyback an additional response onto 
the responses of the factory-installed system. Therefore, it is impossible 
to obtain the added, optional function independent of the underlying 
function of the factory-installed system. In these systems merely pressing 
the lock/unlock switch on the car door can have unintended consequences 
that are undesirable, and potentially dangerous. 
In vehicles that have these add-on systems a child playing with that door 
lock switch could not only lock the door but start the engine, exposing 
the child to carbon monoxide fumes. Even an adult driver would be caught 
off guard if, while the driver is waving goodby and pressing the door 
lock/unlock switch on the car door, the driver's-side window suddenly 
rolls up| 
SUMMARY OF THE INVENTION 
A vehicle security system expander in accordance with the present invention 
comprises a detector for detecting a control output from security system 
control module and an identifier for determining when the output of that 
system control module is produced by operation of the remote control unit. 
Also there is a supplemental control unit which provides a given auxiliary 
function when the output detected by the system control module is produced 
by actuation of the remote control unit. 
In one embodiment the origin of the output is determined by comparing the 
voltages of a remote control output signal of said security system control 
module to the voltage of the output signal of a local control switch. 
In another embodiment, the origin of the output is determined by comparing 
the timing of the output signal of said security system control module to 
the timing of the output signal of a local control switch. 
In a preferred embodiment the invention further includes a timer for 
measuring a predetermined time period in response to receipt of a remote 
control signal and a detector for detecting signals within said time 
period.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows an electro-mechanical rocker-type switch 10 that cooperates 
with a factory-installed remote-control receiver 12 to control the 
actuator 14, which is a solenoid, vacuum switch or stepper motor that 
operates the door lock on the driver's side of the vehicle. The 
installation of such two-wire control circuits is preferable for safety 
reasons, but often more costly than single-wire circuits. 
Pressing down on side "A" of the rocker switch causes the contact on side 
"A" to remain grounded but causes the contact on side "B" to connect the 
lock actuator to the 12-volt dc supply. This opens the lock on the 
driver's door. Pressing down on side "B" of the rocker switch causes the 
contact on side "A" to connect the lock actuator 14 to the 12-volt supply 
line in the opposite direction, reversing the movement provided by the 
actuator. This re-locks the driver's door. 
Alternatively, an rf remote-control signal received by the basic remote 
control receiver module 12 that is commonly installed as standard 
equipment, will produce a pulse on either the "open" or the "lock" output 
on this receiver module 12. Thus these "open" and "lock" output connect 
respective sides of the door lock actuator 14 to the 12-volt supply line, 
without actuating the rocker switch 10. Commonly, the remote control 
transmitter has a respective "lock" and "unlock" button. Some units also 
have an additional button for lights or trunk release. 
FIG. 2 shows a single-wire electro-mechanical rocker switch 30 and basic 
remote-control receiver module 32 that control the lock actuator 14. Here, 
a single moveable contact floats at a 12-volt potential until pressed into 
contact with side "A" or side "B" to open or lock the driver's side door 
lock by connecting a respective out-board relay 34, 36 to the 12-volt dc 
line, which in turn connects the door lock actuator 14 to the 12-volt 
supply line. The out-board relays 34, 36 can also be selectively connected 
to the 12-volt supply by the receiver module 32. This circuit may be 
preferred for its ease of installation, noted above. 
Function expanders are add-on units that upgrade the operation of these 
basic modules 12, 32, by responding to multiple actuations of the rf 
remote-control transmitter that operates the basic receiver module 12. 
That multiple actuation simply results in a multiplication of the pulses 
output by the reciever. 
In the circuits shown in FIGS. 1 and 2, however, a pulsed output can be 
produced by actuation of their rocker switches 10, 30, as well as by an 
output from the receiver modules 12, 32. Thus, inadvertent re-actuation 
of, or contact bounce in, these rocker switches 10, 30 will produce pulses 
that can be mistakenly decoded as an auxiliary function command by the 
microprocessors that monitor those outputs. 
FIG. 3 shows a function expander 40 in accordance with the present 
invention installed as an add-on to the two-wire remote-control module 
shown in FIG. 1. The microprocessor 42 of this expander 40 is installed on 
the remote-control receiver module 12 of FIG. 1 in parallel with actuator 
14. 
This expander 40 detects the origin of the first pulse appearing on either 
the "lock" or "unlock" input to the microprocessor, to eliminate local 
triggering of the auxilliary functions. In the quiescent state, switches 
A3, A4 and B3, B4 of the expander are set so as to select either 
comparator inputs C1 and C2 or timing inputs T1, T2, T3 and T4, 
respectively. These switches may be on-board dual in-line package (DIP) 
switches accessible on the expander unit 40, as shown, or 
software-selectable switches internal to the processor 42. 
In FIG. 3, if the remote control unit produces a 12 V logic high at A1 or 
B1, a logic high appears on processor input C1 or C2, respectively. If a 
contact in switch 10 produces a 12 V high on A3 or B3 that signal also 
propagates from the switch 10 to A1 or B1 across a voltage drop in the 
receiver 12 such that A1 or B1 are reduced below the voltage level 
appearing at A3 or B3, respectively. Similarly, if the pulse originated in 
the local door switch 10, the pulse that appears at A1 or B1 will also lag 
A3 or B3 by an interval reflecting the gate delay inside the receiver 12. 
These relationships in some vehicles may be reversed: the impedance losses 
and lags in the wiring being greater than those encountered across the 
receiver 12, or the relative lag, or the voltage drop being too small to 
be reliably detected. Therefore, to assure reliable operation of this 
verification circuit in after-market expanders that are intended for use 
in a wide variety of vehicles, the settings of switches A3, A4, B3 and B4 
and also the relative levels detected by the comparators 44, 46 are 
preferrably software-selectable. 
Auxilliary functions are initiated by toggling between logic levels, or by 
a trigger pulse having a software-selectable duration. Conventionally, 
function initiation requires a 800 milliampere ground pulse between 800 
milliseconds and 8 seconds in duration, or toggling a 800 milliampere 
current between logic states. These paramters of the signals appearing at 
function outputs F1-F5 on the expander 40 are software-selectable, and the 
outputs are all current-limited to protect the microprocessor. 
The combination of multiple pulses detected by the processor 42 on the two 
outputs of this receiver module 12 are treated as digitally-encoded 
commands for initiating five additional auxilliary functions. The 
processor 42 is connected in parallel with the actuator 14, to monitor 
those pulsed outputs on the "lock" and "unlock" outputs and decode them. 
To prevent false signals produced by electrical interference from affecting 
the microprocessor, the microprocessor only responds to codes it receives 
within a finite time window following the first verified pulse. The window 
is opened by the first input received from either the lock or the unlock 
terminal of the receiver. 
Any complementary functions that the basic receiver controls by providing 
pulses on respective separate output terminals in response to respective 
additional buttons on the transmitter, can also be used to provide 
auxilliary function codes in accordance with the present invention. Such 
codes are particularly advantageous in that they can be implemented 
without necessarily changing the status of the underlying basic function 
provided by the respective additional buttons on the remote control 
transmitter. 
FIG. 4a shows a standard 800 millisecond door-lock output pulse in trace A 
that can be used to open the three-second window. A much shorter, 300 
millisecond door-lock output pulse, shown in trace B, will also open the 
three-second window, as shown in trace C. 
In either case, once the three-second window is open, verified combinations 
of door-lock and door-unlock pulses that are received within that 
three-second time window will initiate respective auxilliary functions. 
For example, the door-lock output alone can easily provide both auxilliary 
functions #1 and #2, as shown for voltage-verified expander apparatus in 
traces D and E. These pulses appearing at A1 are compared to the voltage 
level at A3 for verification. 
The door-unlock pulse shown in trace F could produce any one of three 
different functions, depending on whether it appeared in the three-second 
window alone or in combination with either trace D or trace E. 
In these traces, the pulses in the auxilliary function codes are all 
verified. In accordance with one preferred embodiment of the present 
invention, all unverfied pulses would be disregarded. At least the first 
pulse received by the processor 42 should be verified, to eliminate most 
instances where the auxilliary decode window might be opened by a 
locally-originated pulse rather than a pulse originated by the 
remote-control transmitter. 
FIG. 4b shows a standard 800 millisecond door-lock pulse appearing at A1 
that provides a timing-verified doorlock pulse for auxiliary function #1. 
The three-second window for decoding remote-control functions opens after 
the coincidence-timing of the first pulse received is verified by 
detecting a slight lag in the appearance of this pulse at point A3 in the 
circuit. 
FIG. 5 shows the logical flow of the auxiliary function decoding process. 
The system shown in FIG. 5 uses coincidence timing to validate the 
auxiliary function signal. 
The invention has been described with particular reference to the 
presently-preferred embodiments of the invention. It will be apparent to 
one skilled in the art that modifications and variations are possible 
within the spirit and scope of this invention. For instance, the invention 
may be implemented by installing the expander on the prior art remote 
door-lock circuit shown in FIG. 2, where voltage verification relative to 
the 12 V source timing verification. The invention is defined by the 
appended claims.