Digital touch operated switch

A touch operated switch for control of electrical lighting, appliances, machinery and equipment which requires non sparking fail-safe operation. The switch utilizes digital complementary metal oxide semi-conductor technology which requires nearly insignificant standby power and incorporates a unique count down reset circuit which prevents extraneous operation from static discharge, radio frequency (RF) signals or power line transients. The switch will only respond to the electromagnetic flux generated by the power source that the controlled load is connected to. All other signals or pulses of differing frequencies are ignored by the switch thereby preventing inadvertent operation. Due to the limited number of discreet components utilized the total cost of manufacture will be extremely low and is expected to be less than the present manufacturing cost of the standard wall-type light switches that this invention will replace. The switch also simplifies inventory control due to the fact that a single switch type replaces all of the multi-pole mechanical switches currently utilized to provide switching capability from various locations.

SUMMARY OF THE INVENTION 
A touch operated switch for control of electrical lighting, appliances, 
machinery and equipment which requires non sparking fail-safe operation. 
The switch utilizes digital complementary metal oxide semi-conductor 
technology which requires nearly insignificant standby power and 
incorporates a unique count down reset circuit which prevents extraneous 
operation from static discharge, radio frequency (RF) signals or power 
line transients. Due to the limited number of discreet components utilized 
the total cost of manufacture will be extremely low and is expected to be 
less than the present manufacturing cost of the standard wall-type light 
switches that this invention will replace. 
There are presently on the market numerous touch operated switches and most 
of them fall onto one of the two following catagories: 
The majority of touch operated switches presently available employ high 
impedance 60 Hertz flux actuated circuits. These circuits are susceptable 
to operation by stray radio frequency signals, static discharge and power 
line transients. These types of touch actuated switches also exhibit 
erratic operation in the presence of electronic motor speed controller and 
lamp dimmers. 
To overcome the erratic and extraneous operational characteristics of the 
above type of touch switch technology, a second category of touch switch 
utilizing body heat, infra-red radiation and/or special filters is 
available. These switches are utilized in hospital operating rooms, 
ordinance facilities and other areas where possible explosive atmospheres 
necessitate non-sparking touch type switches for control and illumination 
of electrical equipment in addition to the required reliability 
characteristics, these switches are also quite expensive. 
The most common switches on the market, the standard single pole single 
throw "light switches", are mechanically operated and open or close a 
circuit by either shorting a set of contacts or by causing a small 
quantity of mercury to bridge a gap between conductors within a sealed 
container. The switch must be configured to handle the maximum current 
which flows through the controlled circuit. This means that the wire size 
which is required to handle the load current is the same size which must 
be connected to the switch and all voltage drop and "copper loss" 
calculations apply to the switch wires as well as to the wire which brings 
the power from the main distribution panel to the load. This also means 
that any change in the switch location requires rewiring of the circuit 
and in most cases is accompanied by structural changes in the facility 
which makes most electrical system changes cost prohibitive. 
OBJECTS AND ADVANTAGES OF THE INVENTION 
In view of the foregoing, it is an object of this invention to provide a 
reliable, solid-state, touch operated switch for all applications which 
presently utilize mechanical switches. These applications include all 
appliance, machinery and illumination controls. 
It is another major object of this invention to provide a solid-state 
digital count and reset circuit which initiates switch activation when 
desired and prevents activation from extraneous sources, the switch 
utilizing circuitry which requires less than one watt of stand-by or 
operating power. 
Another object of this invention is to provide a non-sparking, 
ultra-reliable, low-cost, touch operated switch for all applications which 
require low voltage remote operation similar to the expensive touch switch 
technology currently utilized in hospitals and other special or hazardous 
facilities. 
A further object of this invention is to provide an extremely reliable, low 
cost, rugged and compact, long lasting touch operated switch which, due to 
its inherent invulnerability to extraneous signal activation, permits the 
switch to replace existing mechanical (wall light) switches and which can 
be installed by the average do-it-yourself individual. This touch operated 
switch provides a low sensor inputs from several physically separated 
touch sensitive sources and still provide positive control of the load. 
Still another object of this invention is to provide remote switching 
capability in the average home which permits the occupants to control 
electrical circuits in the home from remote locations, and to change the 
controlling location at will, without the necessity of rewiring the 
system. The touch operated switches can be coded to require any number of 
input pulses to actuate the circuit, thereby permitting adapting of the 
switch for controlling heavy machinery, safety circuits, or special 
security installations. In addition, the switch utilizes a unique internal 
timer to provide the hysteresis necessary for single point switch 
activation "on" or "off", and further provides an inherent emergency 
signalling capability by a person maintaining continuous contact with the 
sensor. 
The foregoing as well as other objectives and advantages of this invention 
may be more clearly understood by reference to the following detailed 
description which when taken with the drawings illustrate certain aspects 
of the present invention.

PREFERRED EMBODIMENTS 
In FIG. 1, the invention major components are represented by numerals 1-18. 
The touch sensor, numeral 1, is connected either directly or by shielded 
wire to the switch circuit via an isolation network, 2. A person or object 
touching the sensor causes a capacitive coupling to ground of 
approximately two hundred (200) pico farads which provides a signal path 
for the "sine wave" power line induced pulses. These pulses occur at a 60 
hertz rate (line frequency) in the United States and at 50 hertz in most 
of Europe. The pulses, at the power line frequency are coupled by the 
isolation network, 2, to the input of a Schmitt Trigger, 3. The Schmitt 
Trigger, 3, provides the hysteresis necessary to isolate the follow 
circuits from the spurious effects of noise of the input signal. The 
Schmitt Trigger, 3, also generates fast transitions from the slow rising 
"sine wave" input signals. The symetrical square wave output of the 
Schmitt Trigger, 3, is connected to the clocking input of the digital 
count-down circuit, 4, which is the heart of this invention. 
The digital count-down circuit, 4, is a divide by "N" counter which is 
configured by the manufacturer to permit an output only after a 
predetermined number of sensor input pulses are received. The sensor input 
counter, 4, is also provided with a reset capability which, when 
activated, causes the counter, 4, to reset and begin the sensor signal 
pulse count at "0". The reset pulse for the sensor counter, 4, reset 
circuit is derived from a second digital countdown circuit, 5. The second 
counter, 5, is also a divide by "N" circuit which is configured by the 
manufacturer to provide an output only after a predetermined number of 
input pulses are received. The line counter, 5, is set to provide an 
output at a number greater than the number selected for the sensor 
counter, 4. Therefore if the sensor counter, 4, is configured to provide 
an output of the 16th pulse, the line counter, 5, would be required to 
provide a reset pulse at some number greater than 16, or if the same 
number of pulses is desired for both counters 4 and 5 the sensor counter 
would be configured to increment on the leading edge of each pulse while 
the line counter, 5, increments only on the pulse trailing edge. A pulse 
leading edge is considered to be the low to high transition of the square 
wave and trailing edge is the high to low transition. 
The input pulses for the line counter, 5, are derived directly from the 
power line serving the switched circuit. The power line is connected to 
the input of a Schmitt Trigger, 6, which provides the same function for 
the power line signals as the Schmitt Trigger, 3, does for the sensor 
signals. It is understood, then, that the sensor counter, 4, can only 
provide an output if it receives the proper number of input pulses prior 
to receiving a reset pulse from the line counter, 5. As an example, in 
practice, assume that contact is made with the sensor, 1, initiating the 
sensor count at the same instant that the line counter, 5, has reached a 
count of "3". Assume also that the sensor counter, 4, requires a count of 
16 to generate an output and that the line counter, 5, provides a reset 
pulse on the 17th count. The sensor counter, 4, will have only reached a 
count of "14" by the time the line counter, 5, reaches "17", generates an 
output, and causes the sensor counter, 4, to reset to "0". In order for 
the sensor counter, 4, to generate an output, contact with the sensor must 
be maintained for an additional 16 pulses at the power line frequency. In 
the above scenario, the total time between initiation of contact and the 
generation of an output by the sensor counter, 4, is one half (1/2) second 
in a 60 hertz circuit. This is determined by adding the first fourteen 
(14) pulses, prior to system reset, to the sixteen (16) pulses required 
for operation. 
The delay circuit timer, 7, generates an output when an input signal is 
received from the sensor counter, 4. The delay circuit timer, 7, is 
configured to ignore inputs received at a rate greater than one (1) per 
one half (1/2) second. This prevents sudden on/off applications of line 
power to the switched load which would be caused by failure of the person 
or object touching the sensor, 1, to break contact immediately following 
switch activation. The scenario above required sixteen (16) pulses for 
switch activation, therefore, continuous contact with the sensor, 1, will 
cause the sensor counter, 4, to generate an output at a rate just slightly 
less than four (4) times per second, however, the timer prevents switch 
operation at a rate greater than approximately once per second. The delay 
circuit timer, 7, permits an apparently immediate operation of the switch 
upon contact with the sensor, 1, but also provides a comfortable time 
delay to enable breaking contact when the desired switch action (on or 
off) is accomplished. Continuous contact with the sensor, 1, will cause 
the switch to cycle on and off at approximately the rate determined by the 
delay circuit timer, 7, which permits utilization of the switch for 
emergency signaling, advertising, or warning applications. 
Operation of the Triac, 9, is also fairly well understood. The Triac 
functions as a solid-state switch which permits electrical current flow 
between the main terminals, 11 and 12, only when the proper voltage is 
applied to the gate terminal, 10. When the flip-flop, 8, output is in the 
"on" state, gate voltage is applied to the Triac, 9, gate terminal, 10, 
allowing current flow between terminals 11 and 12, which causes power to 
be applied to the load, 13. When the flip-flop, 8, is off, the Triac, 9, 
gate terminal, 10, is grounded which causes the Triac to exhibit an "open 
circuit" between the main terminals, 11 and 12, preventing application of 
electrical power to the load. 
Standby power for the touch operated switch is derived from the power line 
and utilizes the capacitive reactance (Xc) of a small capacitor, 14, to 
provide the voltage drop necessary for system operation. The main 
advantages of capacitive reactance utilization as opposed to resistance 
for voltage drop is that the current across the capacitor leads the 
voltage by approximately 90 degrees which means a nearly "0" power factor. 
Since power dissipation is calculated by multiplying the voltage drop by 
the current flow by the power factor, it is readily seen that only an 
insignificant amount of power is lost in heat by utilization of a 
capacitor, 14, in the touch operated switch power supply, 16. Capacitor, 
15, is utilized, in conjunction with two diodes within the integrated 
circuit, to provide the filtered direct current (DC) supply necessary for 
system operation. 
The extremely high input impedance inherent in CMOS logic elements, 
(approximately 1.times.10 megohms) and the very low leakage 
characteristics exhibited by modern large molecule plastic dielectric 
capacitors combine to provide the invention with memory capability which 
does not require battery backup during power line interruptions. Memory 
retention is provided by the fact that CMOS devices require supply current 
only when actually counting or switching, therefore, when the input power 
is interrupted, the only requirement for memory retention is to maintain a 
static voltage across the flip-flop, 8, supply terminals until power is 
restored. The necessary static charge is provided by capacitor, 18. 
Capacitor, 18, is connected across the flip-flop, 8, supply terminals and 
during normal switch operation is charged through diode, 17. The diode, 
17, prevents discharge of capacitor, 18, through other elements of the 
touch switch when line power fails. When line power is restored following 
an interruption the flip-flop, 8, output state will be as it was when the 
interruption occurred. The touch switch memory feature is particularly 
desirable in those applications where the switch controls power to 
equipment such as a furnace, air conditioner, water pump, security 
lighting, or other normally unattended switching applications. 
FIG. 2 illustrates the touch switch configured as a direct replacement for 
standard toggle type wall switches. The monolithic very large scale 
integrated circuit (VLSIC) is totally encapsulated in a non-conductive 
plastic compound, 19, to protect the circuit from environmental conditions 
and to provide a low cost unit package. The switch is provided with three 
color coded wires and instructions for installing in accordance with the 
"National Electrical Code". A switch box cover plate, 20, either blank or 
decorative, will be provided with each switch. 
In applications which normally require two or more switches, such as 
"2-way" and "3-way" circuits, the present invention will perform the same 
function with only one switch. FIG. 3 depicts the conventional prior art 
method for wiring a typical stair light for control from two locations. 
Input power from the circuit breaker or fuse panel is connected to a 
single-pole-double-throw (SPDT) switch, 21. The black "hot" wire is 
switched to either the black or red wire which is connected between the 
switches 21 and 22. The second SPDT switch, 22, selects either the black 
or red wire as an input and, depending on the position of switch 21, 
applies or removes the line power to the lighting fixture, 23. As the 
number of switch positions increases, the wiring complexity, switch cost 
and number of conductors required for hook-up increases accordingly. 
FIG. 4 schematically depicts a typical installation which provides for 
control of a remote light from several sensors but utilizes only one unit 
of the present invention. The touch operated switch, 24, is installed in 
the first Box 25 between the supply voltage and the light fixture, 26. The 
box cover plates, 28, are connected together by low cost shielded wire, 
27, and contact with any one of them will cause switch activation. 
FIG. 5 depicts a duplex electrical outlet, 29, with molded in touch switch 
sensor connected, 30, in the box cover, 31. A typical remote sensor is 
schematically depicted by FIG. 6. The sensor itself is any conductive 
object, 1, mounted on a nonconductive base, 32. The conductive object, 1, 
is connected to the shielded conductor of wire, 27. The wire, 27, can be 
any convenient length. Lengths of six, twelve and eighteen feet have been 
successfully employed with the engineering development models. The 
shielded wire, 27, is terminated in a standard "RCA" type plug, 33, which 
mates with the connectors installed in the duplex oulet covers illustrated 
in FIG. 5. It should be noted that and "RCA" type jack will also be 
installed in all units employing the touch switch unless the unit is 
provided with an integral sensor such as the wall switch depicted by FIG. 
2. FIG. 7 represents an example of the touch switch utilization in a 
typical residence. As shown, at least one electrical outlet in each room 
would be provided with the unit depicted by FIG. 5. The duplex electrical 
outlets will be wired normally in accordance with existing code 
requirements and the associated sensor connector, 30, would be connected 
to a centralized switch matrix panel, 35, by low cost American Wire Gage 
(AWG) size 24 shielded wire. 
The purpose of the switch matrix, FIG. 8, is to permit a user to control a 
number of remote electrical circuits from selected sensor locations and to 
change the selected locations at will without the necessity of rewiring 
the system. 
Again, referring to FIG. 7, in establishing the system operating 
configuration, a user need only determine which electrical circuits are to 
be controlled from which sensor location and then activate the appropriate 
matrix junction by inserting a plastic pin at the appropriate 
intersection. The panel, 35, operates in classic matrix fashion in that 
contact at a junction completes the circuit between the associated row and 
column functions. Each controlled circuit is initially wired to a touch 
operated switch which is installed in the matrix panel. The actual touch 
switch modules, 24, are plug-in units to enable the system to accommodate 
various power load requirements and to afford the system maximum 
flexibility. 
The switch module, 24, sensor inputs are connected to designated "columns" 
within the matrix, 34, and the circuits are identified in the indicated 
spaces across the top. Each remote sensor cable is connected to a "row" 
and the associated location is indicated in the horizontal spaces 
extending down the side of the matrix switch, 34. Insertion of a plastic 
pin in a hole in the switch causes electrical connection between the 
selected "row" and "column". The selected circuits are then controlled by 
physical contact with the sensors (FIG. 6) plugged into the appropriate 
remote connectors. A selected circuit can also be controlled from several 
locations if desired. 
In practice, the touch operated switch described herein has proven to be 
extremely reliable in operation. Twenty (20) versions of the switch have 
been constructed for testing. The units have been subjected to a combined 
total of over 150,000 hours of operation and the only failures were 
attributed to discrete components which will not be utilized in production 
units. All of the test units utilized integrated circuits of the 
complementary metal oxide semiconductor (CMOS) logic family to assure 
reliable operation with minimal standby power consumption. The switched 
loads consist of both incandescent and fluorescent lighting, a vacuum 
cleaner, a wood turning lathe, electric drills, a router and other power 
tools. In all cases, the switch performed without fault. 
Although each of the development models of the test switch utilized 
individual integrated curcuits and other discrete components, production 
models of the switch will employ large scale integration (LSI) techniques 
which will reduce the number of discrete components required. This will 
allow total encapsulation of the units to provide immunity from shock, 
vibration and moisture. It also provides for small size and low cost 
packaging. 
In view of the foregoing, specific forms of the present invention have been 
described in detail. Modifications, however, may occur to those skilled in 
the art without departing from the spirit of the present invention.