U.S. patent application number 10/356239 was filed with the patent office on 2003-08-14 for electrical switch and method of generating an electrical switch output signal.
This patent application is currently assigned to Easter-Owen Electric Company. Invention is credited to Easter, David A., Karnowka, Thomas P., Milby, Douglas K., Rosenberg, Armand, Teen, Timothy N..
Application Number | 20030150702 10/356239 |
Document ID | / |
Family ID | 26830949 |
Filed Date | 2003-08-14 |
United States Patent
Application |
20030150702 |
Kind Code |
A1 |
Karnowka, Thomas P. ; et
al. |
August 14, 2003 |
Electrical switch and method of generating an electrical switch
output signal
Abstract
An electrical switch and a method of generating an electrical
switch output signal. An electric switch senses both pressure
placed upon the switch's surface and the contact of the object
exerting the pressure on the switch. When both conditions exist,
the switch is activated. The electrical switch may employ a
piezoelectric element to recognize the application of pressure, a
capacitive sensing circuit to recognize the presence of an object
applying the pressure, and a microcontroller circuit to control
output switch circuity upon satisfaction of both conditions
precedent. The electrical switch can be configured to provide a
continuous output signal for the duration that the switch is
pressed after the conditions are satisfied or to switch between
open and closed states each time the switch is pressed after the
conditions are satisfied.
Inventors: |
Karnowka, Thomas P.;
(Littleton, CO) ; Easter, David A.; (Arvada,
CO) ; Teen, Timothy N.; (Randolph, NJ) ;
Milby, Douglas K.; (Arvada, CO) ; Rosenberg,
Armand; (Rehovoth, IL) |
Correspondence
Address: |
Robert E. Purcell
Wall Marjama & Bilinski LLP
Suite 400
101 S. Salina Street
Syracuse
NY
13202
US
|
Assignee: |
Easter-Owen Electric
Company
|
Family ID: |
26830949 |
Appl. No.: |
10/356239 |
Filed: |
January 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10356239 |
Jan 31, 2003 |
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09552837 |
Apr 20, 2000 |
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6522032 |
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60133002 |
May 7, 1999 |
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Current U.S.
Class: |
200/81R |
Current CPC
Class: |
H03K 17/96 20130101;
H03K 17/964 20130101; H03K 17/962 20130101 |
Class at
Publication: |
200/81.00R |
International
Class: |
H01H 035/24 |
Claims
What is claimed is:
1. An electrical switch comprising: a switch actuation surface
adapted to receive an object pressed thereagainst; pressure sensing
means for sensing the condition of an object being pressed against
said switch actuation surface; pressure sensing signal means for
generating a pressure sensing electrical signal in response to said
pressure sensing means sensing said pressed against condition;
presence sensing means for sensing the presence of said object in
the vicinity of said switch actuation surface; presence sensing
signal means for generating a presence sensing electrical signal in
response to said presence sensing means sensing the presence of
said object in the vicinity of said switch actuation surface;
determining means responsive to both said pressure sensing signal
means and to said presence sensing signal means for determining
whether said pressure sensing electrical signal is generated within
a predetermined time interval of which said presence sensing
electrical signal is generated; and means responsive to said
determining means for generating an electric switch output signal
if said determining means determines that said pressure sensing
signal is generated within said predetermined time interval.
2. An electrical switch according to claim 1 wherein said pressure
sensing means includes a piezoelectric element.
3. An electrical switch according to claim 1 wherein said presence
sensing means includes a photovoltaic cell in which a light beam is
interrupted by said object.
4. An electrical switch according to claim 3 wherein said presence
sensing means includes an electrically conductive medium and
capacitive sensing means for sensing a capacitive change in said
conductive medium.
5. An electrical switch according to claim 4 wherein said switch
actuation surface includes said conductive medium.
6. An electrical switch according to claim 3 wherein said pressure
sensing means includes a piezoelectric element.
7. An electrical switch according to claim 4 wherein said pressure
sensing means includes a piezoelectric element.
8. An electrical switch according to claim 5 wherein said pressure
sensing means includes a piezoelectric element.
9. An electrical switch according to claim 1 wherein said
determining means determines whether said pressure sensing
electrical signal is generated within a predetermined time interval
after said pressure sensing signal is generated.
10. An electrical switch comprising: an electrically conductive
casing, at least one piezoelectric element, a microcontroller,
whereby said casing supports said piezoelectric element, whereby
said microcontroller is electrically connected to said casing to
sense a change in said casing's capacitance above a predetermined
threshold caused by contact with a conductive object, whereby said
microcontroller is electrically connected to said piezoelectric
element to sense a change in said piezoelectric element's voltage
caused by pressure applied to said piezoelectric element, whereby
said microcontroller opens or closes said electrical switch in
response to sensing a change in said casing's capacitance above a
predetermined threshold and sensing a change in said piezoelectric
element's voltage.
11. An electrical switch according to claim 10 wherein said
microcontroller includes a timer for monitoring time of a
preselected duration whereby if said microcontroller senses a
change in said casing's capacitance above a predetermined threshold
said microcontroller initiates said timer and if said
microcontroller senses a change in said piezoelectric element's
voltage prior to the expiration of said predetermined timer
duration, said microcontroller opens or closes said electrical
switch.
12. An electrical switch according to claim 10 wherein said
microcontroller produces an output pulse of a predetermined
duration when said microcontroller opens or closes said electrical
switch in response to sensing a change in said casing's capacitance
above a predetermined threshold and sensing a change in said
piezoelectric element's voltage.
13. An electrical switch according to claim 10 wherein said timer's
preselected duration is between 0.1 and 2.5 seconds.
14. An electrical switch according to claim 10 wherein said
piezoelectric element is electronically connected to said
microcontroller by a flexible leadless connector.
15. An electrical switch according to claim 10 wherein said
microcontroller is mounted within said casing.
16. An electrical switch according to claim 10 possessing internal
power supply circuitry.
17. An electrical switch according to claim 10 which provides
switch closure for the duration that pressure is provided to said
piezoelectric element and an object is in contact with said
casing.
18. An electrical switch according to claim 10 which alternates
between switch closure and opening each instance pressure is
provided to said piezoelectric element and an object is in contact
with said casing.
19. An electrical switch, comprising: a cylindrical electrically
conductive casing with a length, two opposing open distal ends, an
exterior surface and an interior chamber formed from said interior
surface; a flexible cap mounted over one of said distal open ends
with a surface accessible to pressure input and a second inner
surface opposite said first surface facing said interior of said
chamber; a support frame mounted within said interior of said
chamber in contact with said cap's second inner surface; at least
one piezoelectric element mounted in said support frame within said
interior of said chamber with a contact surface to receive
transmitted pressure input from said cap and an opposing voltage
transmission surface; piezoelectric signal conditioning circuitry
mounted within said interior of said chamber and electrically
connected to said piezoelectric element's voltage transmission
surface; capacitive sensing circuitry mounted within said interior
of said chamber; power supply circuitry mounted within said
interior of said chamber; a microcontroller mounted within said
interior of said chamber electrically connected to said
piezoelectric signal conditioning circuitry and electrically
connected to said capacitive sensing circuitry and driven by said
power supply circuitry; switch circuitry mounted within said
interior of said chamber electrically connected to and controlled
by said microcontroller outputs; interface terminals electrically
connected to said switch circuitry and extending through said
second distal end of said electrically conductive casing to said
exterior of said electrically conductive casing.
20. An electrical switch according to claim 19 wherein said cap is
incorporated into said electrically conductive casing.
21. An electrical switch according to claim 19 wherein said
piezoelectric element's voltage transmission surface is
electronically connected to said microcontroller by a flexible
leadless connector.
22. An electrical switch according to claim 19 wherein said
microcontroller, capacitive sensing circuitry, and switch circuitry
are mounted on at least one printed circuit board.
23. An electrical switch according to claim 19 which provides
switch closure for the duration that pressure is provided to said
piezoelectric element and an object is in contact with said
casing.
24. An electrical switch according to claim 19 which alternates
between switch closure and opening each instance that pressure is
provided to said piezoelectric element and an object is in contact
with said casing.
25. An electrical switch comprising: an electrically conductive
casing; pressure input sensing means for generation of a pressure
presence signal when pressure is exerted on the exterior of said
electrically conductive casing; proximity detecting means for
generation of a contact signal when an object comes into contact
with the exterior of said electrically conductive casing; detection
means for acknowledging concurrent existence of said pressure
presence signal and said contact signal; control means being
responsive to said detection means and operative to provide switch
opening or closure.
26. An electrical switch according to claim 25 wherein said control
means provides switch closure for the duration of the existence of
said pressure presence signal and said contact signal.
27. An electrical switch according to claim 25 wherein said control
means alternates between switch opening and closure upon each
individual instance that said pressure presence signal and said
contact signal concurrently exist.
28. An electrical switch according to claim 25 wherein said
pressure input sensing means comprises a piezoelectric element.
29. A method of opening and closing an electrical switch comprising
the steps of: (a) sensing the input of pressure on an electrical
switch; (b) sensing the presence of an object in contact with an
electrical switch; (c) sensing whether electrical switch is closed;
(d) opening the electrical switch if the electrical switch is
closed and pressure was applied concurrently with an object
contacting the electrical switch; (e) closing the electrical switch
if the electrical switch is open and pressure was applied
concurrently with an object contacting the electrical switch.
30. The method of claim 29 wherein step (b) occurs prior to step
(a).
31. The method of claim 29 wherein step (a) and step (b) occur
simultaneously.
32. A method of opening or closing an electrical switch comprising
the steps of: (a) sensing the input of pressure on an electrical
switch; (b) sensing the presence of an object in contact with an
electrical switch; (c) closing the electrical switch if pressure
was applied concurrently with an object contacting the electric
switch; (d) monitoring the continual contact of the object in
contact with the electrical switch; (e) opening the electrical
switch when the object in contact with the electrical switch is
removed.
33. The method of claim 32 wherein step (b) occurs prior to step
(a).
34. The method of claim 32 wherein step (a) and step (b) occur
simultaneously.
Description
[0001] This application is based upon a provisional application
filed on May 7, 1999 with a Serial No. of 60/133,002, and is hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to electric switches, and more
particularly pertains to an improved piezoelectric switch
incorporating a unique system of discerning between deliberate
touch activation and various other false trigger possibilities
which can provide information concerning the duration of the
activating contact.
[0003] Mechanical activated switches provide switch control
capabilities, but are affected by environmental factors such as
extreme temperature variations and moisture and are subject to
degradation due to wear, which can limit such switch's life and
effectiveness. Non-mechanical, electrical switches, like
piezoelectric switches, avoid the life limiting wear
characteristics inherent to mechanical switches, but are subject to
false activation.
[0004] The present invention provides an improved electrical switch
which possesses the ability to detect the occurrence of when an
object such as a human finger applies pressure to the switch and
the ability to monitor the duration of the presence of such object
in contact with the switch. The present invention, therefore, can
provide a relatively accurate, controlled means of discerning
between intentional switch actuation and anomalies which might
cause unintentional activation as well as provide an accurate
measure of the duration of the switch activation contact.
[0005] The present invention is broad enough to contemplate an
electrical switch which monitors two separate conditions. The
preferred embodiment, described in detail subsequent, monitors
actuation pressure applied to the switch and capacitive change in
the switch's case caused by contact with a conductive object, such
as a human finger. By requiring these separate conditions
precedent, the switch avoids actuation by pressure placed upon the
switch inadvertently, such as by incidental contact or by sound
waves or atmospheric variations, and avoids actuation by only
conductive contact with the switch, such as by contact with
inadvertent liquid spills, humidity, or rain.
SUMMARY OF THE INVENTION
[0006] The present invention contemplates an electrical switch and
a method of generating an electrical switch output signal. The
electric switch senses both pressure placed upon the switch's
surface and the contact of the object exerting the pressure on the
switch. When both conditions exist, the switch is activated. The
electrical switch may employ a piezoelectric element to recognize
the application of pressure, a capacitive sensing circuit to
recognize the presence of an object applying the pressure, and a
microcontroller circuit to control output switch circuity upon
satisfaction of both conditions precedent. The electrical switch
can be configured to provide a continuous output signal for the
duration that the switch is pressed after the conditions are
satisfied or to switch between open and closed states each time the
conditions are satisfied
[0007] While the above are important features of the invention,
there are, of course additional features of the invention that will
be described hereinafter and which will form the subject matter of
the claims appended hereto. In this respect, before explaining at
least one preferred embodiment of the invention in detail, it is to
be understood that the invention is not limited in its application
to the details of construction and to the arrangements of the
components set forth in the following description or illustrated in
the drawings. The invention is capable of other embodiments and of
being practiced and carried out in various ways. Also it is to be
understood that the phraseology and terminology employed herein are
for the purpose of description and should not be regarded as
limiting. As such, those skilled in the art will appreciate that
the conception, upon which the disclosure is based, may readily be
utilized as a basis for the designing of other structures, methods,
or systems for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing features of the present invention will be more
readily understood by reference to the following detailed
description taken with the accompanying drawings, in which:
[0009] FIG. 1 is a longitudinal cross-sectional, schematic view of
an electrical switch according to one embodiment of the present
invention;
[0010] FIG. 2 is a schematic diagram of the circuitry of the
embodiment of the present invention shown in FIG. 1;
[0011] FIG. 3 is a flow diagram of the operation of the embodiment
of the present invention shown in FIGS. 1 and 2;
[0012] FIG. 4 is a logic flow diagram of the operation of another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] The present invention will be described with reference to
the accompanying drawings wherein like reference numerals refer to
the same item.
[0014] There is shown in FIG. 1 an electrical switch according to
one embodiment of the present invention. The switch includes a
substantially cylindrical, conductive case 10 possessing a closed
distal end cap 12 and a series of threads about the external
peripheral surface to permit installation of the switch in a
correspondingly threaded aperture in a wall, plate, or other
mounting structure. Thus, the switch may be adapted for a wide
range of applications in a wide variety of mounting structures.
While the preferred embodiment is depicted as a threaded
cylindrical conductive case, the present invention contemplates
cases of various shapes and sizes as well as a variety of
installation means other than those depicted in FIG. 1.
[0015] The closed distal end cap 12 of the case 10 is sufficiently
pliant and elastic to bend slightly (to a deformity of
approximately two or more microns) when the end cap 12 receives
pressure input such as is generated by a person's finger. Standard
human finger pressure is in the range of three to five Newtons. The
distal end cap 12, therefore, is made of a material and is of a
corresponding thickness which can be deflected two or more microns
by ordinary human finger pressure. In the preferred embodiment
described herein, the closed distal end cap 12 of the case 10 may
be integrally formed with the case 10, but need not be. The case 10
may be fashioned of a conductive material such as aluminum,
stainless steel, brass, or any other equivalent rigid, semi rigid,
or non-rigid conductive material. The cap 12 may be fashioned of a
material which is either the same as or different from that forming
the case 10. The preferred embodiment uses a cap 12 that can be
deflected as described previously, however, the invention broadly
contemplates other means of transmitting pressure information such
as push buttons acting against a compression spring or similar
means. A support frame 14 is mounted to the interior surface of the
distal end cap 12 and holds a piezoelectric element 16 having a
contact surface 22 in contact with the distal end cap 12, whereby
pressure applied to the distal end cap 12 in the direction of arrow
17 shown in FIG. 1 is transmitted to the piezoelectric element 16.
The support frame may be fashioned from any non-conductive material
such as plastic, rubber or glass. When pressure is applied to the
contact surface 22 of piezoelectric element 16, the element flexes,
whereby surface charges are induced by the piezoelectric element's
dielectric displacement, and an electrical field is built up within
the piezoelectric element 16. Typical piezoelectric elements
require being flexed less than two microns to generate such an
electric field. Therefore, the pressure transmitted to flex the
piezoelectric element need only be slight.
[0016] The electric field within the piezoelectric element 16 is
transformed into electric voltage on the element's voltage
transmission surface 24. This voltage is transmitted to piezo
signal conditioning circuitry 18 by flexible leadless conductor pad
20. The preferred embodiment utilizes an anisotropic electrical
conductive rubber. The invention, however, contemplates connecting
the piezoelectric element 16 to the piezoelectric conditioning
circuitry by any electrically conductive means. The transmitted
voltage is received by piezo signal conditioning circuitry 18,
which upon receipt of the transmitted voltage, generates a control
signal, which signal is transmitted to the microcontroller
circuitry 32. This signal indicates to the microcontroller that
pressure is applied to the distal end cap 12 of the case 10.
[0017] Microcontroller circuitry 32 incorporates capacitive sensing
circuitry which is electrically connected to the case 10 by
enclosure contact clips 26. Contact by a human finger, hand, or
other conductive object with the closed distal end cap 12 of the
case 10 varies the base capacitance of the case 10 and generates a
contact signal within the microcontroller circuitry 32 in a manner
fully explained below. When the microcontroller circuitry 32
acknowledges the contact signal and receives the control signal
from the piezo signal conditioning circuitry 18, the
microcontroller circuitry 32 selectively instructs output switch
circuitry 34 to provide either an active or an inactive current
sink at interface terminal 28. The microcontroller circuitry 32
selection of active or inactive current sink is more fully
explained below.
[0018] The microcontroller circuitry 32 and piezo signal
conditioning circuitry 18 are both powered by power supply
circuitry 30. The operation of the power supply circuitry 30 is
more fully explained below.
[0019] FIG. 2 is a schematic diagram of the interface terminal 28,
power supply circuitry 30, microcontroller circuitry 32, piezo
signal conditioning circuitry 18, and output switch circuitry 34.
The interface terminal 28 possesses six interface pins. Power
supply circuitry 30 is supplied external voltage, direct current or
alternating current, through interface terminal 28 pin number two.
Series diode 100 conducts only the positive component of the input
waveform and the positive peak of the unregulated input voltage is
then held by capacitor C1. Zener diode 102, biased by resistor 104,
provides a stable reference voltage to the base of transistor Q106.
Load current to power the microcontroller circuitry flows from C1
through the collector of transistor Q106, where the voltage is
dropped to a steady five volts at the emitter of Q106. Capacitor
C108 then provides high frequency decoupling for the
microcontroller power supply.
[0020] Piezo signal circuitry 18 comprises piezoelectric element 16
in parallel with load resistor 136 and spike arrest zener diode
110. Output voltage derived from bending the piezoelectric element
16 turns on transistor 112 dropping input potential to the
microcontroller circuitry 32 from its normally high state (VDD) to
low (gnd/RTN), thereby indicating pressure applied to distal closed
end 12 of the case 10.
[0021] Microprocessor 114 generates an oscillating output waveform
at microprocessor 114 pin number five which is received by
microprocessor 114 pin number seven through resistor 116. When the
switch is untouched, capacitor 118 leaves the output waveform
unaffected. When contact is made with the switch such as human
contact, the capacitance of the case 10 increases. The increased
capacitance appears in series with capacitor 118 through enclosure
contact clips 26. The combined capacitance phase shifts the
oscillating output waveform as the waveform is received at
microprocessor 114 pin number seven. The microprocessor 114 is
internally programmed to recognize this phase shift as contact with
the closed distal end cap 12 of the case 10. The microprocessor 114
can be programmed to recognize any range of capacitive change to
increase or decrease the actuation contact requirement for a
corresponding range of switch sensitivity. While the preferred
embodiment utilizes capacitive sensing circuitry to sense contact
with the case, the invention broadly contemplates other presence
sensing devices which may not require contact with the case. Such
presence sensing devices may include photovoltaic cells in which an
object interferes with the light detection of the cell, magnetic or
electromagnetic field detection circuitry which can sense a change
in magnetic or electromagnetic fields induced by proximate objects,
temperature sensing means which senses change in temperature due to
proximate objects, or any other similar presence sensing
devices.
[0022] When microprocessor 114 receives a low signal from piezo
signal conditioning circuitry 18 and recognizes contact with the
closed distal end cap 12 of the case 10, the microprocessor 114
produces two output signals at microprocessor 114 pins four and
five, one constant and the other a pulse of five hundred
millisecond duration. The five hundred millisecond signal can be
used for a variety of purposes, for example, to create an audible
signal which indicates switch actuation. As the invention is not
limited to these particular output signals, the microprocessor can
be programmed to generate a variety of other outputs signals of
varying duration or to output waveforms in response to recognition
of the two conditions precedent. The output signals are transmitted
to identical circuits within output switch circuitry 34. While the
preferred embodiment utilizes a microprocessor, the invention
contemplates other determining means such as linear logic circuitry
or discrete circuitry.
[0023] The preferred embodiment utilizes output switch circuitry to
provide current-sink outputs which are transmitted through the
interface terminals to external electronic equipment. The invention
is broad enough, however, to contemplate a switch providing actual
electrical continuity between two or more electrical nodes, or the
output of waveforms or various signals responsive to satisfaction
of the two predetermined conditions precedent. To provide
current-sink switch capability, transmitted output signals from the
microprocessor 114 are received at the gates of transistors 120 and
122 across resistors 124 and 126 respectively. High transmitted
output signals turns off transistors 120 and 122 which, in turn,
turns off transistors 128, 130, 132, and 134. When transistors 128,
130, 132 and 134 are off, electrical discontinuity exists between
interface terminal 28 output pin numbers one and three and
ground/RTN. This "inactive current-sink" state is recognized by
external circuitry to be the electrical equivalent of an "open"
circuit. Low transmitted output signals turns on transistors 120
and 122 which in turn turns on transistors 128, 130, 132, and 134.
With transistors 128, 130, 132, and 134 on, electrical continuity
exists between interface terminal 28 output pin number 6 and
ground/RTN, and between interface terminal 28 output pin number 4
and ground/RTN, allowing AC or DC current to flow through each
circuit. This "active current-sink" state is recognized by external
circuitry to be the electrical equivalent of a "closed"
circuit.
[0024] While the preferred embodiment described in FIGS. 1 and 2
and explained above show an electric switch case 10 within which
all circuitry is self contained, the invention should not be so
limited. Variations of the invention are possible whereby all or
some of the elements and circuitry described are electrically
interconnected but separate from the body of the switch. Such
variations would allow for installation in locations where a self
contained switch may be impractical.
[0025] FIGS. 3 and 4 shows the microprocessor's operational flow
for two embodiments of the electrical switch. In FIG. 3, interface
terminal 26 output pins one and three begin in a default "open" or
"inactive current-sink" state. When the case 10 is touched as
described above, the microprocessor 114 senses a change in the
case's 10 capacitance as described previously and initializes a two
second timer. If within the two second period, the piezo signal
conditioning circuitry 18 is activated by pressure as previously
described, the microprocessor 114 sets interface terminal 28 output
pin one to the "closed" or "active current-sink" state and
interface terminal 28 output pin three to the "closed" or "active
current-sink" state for five hundred milliseconds and then resets
interface terminal 28 output pin three to the "open" or "inactive
current-sink" state. The microprocessor 114 then initializes a ten
millisecond timer. If within ten milliseconds, the case's 10
capacitance returns to its initial value due to removal of contact
with the case 10, the terminal 28 output pin remains in the
"closed" or "active current-sink" state until the ten millisecond
time period is over. If the case's 10 capacitance indicates touch
contact has returned prior to the end of the ten millisecond
period, the terminal 28 output pin one remains in the "closed" or
"active current-sink" state, and the microprocessor 114
reinitializes the ten millisecond timer, thereby monitoring the
switch every ten milliseconds until the case 10 is released.. In
this way, the ten millisecond timer allows inadvertent removal of
touch contact with case 10 without resetting terminal 28 output pin
one to an "open" or "inactive current-sink" state. This is a method
of providing a switch "debounce". If the case's 10 capacitance
remains at its initial value at the end of the ten millisecond
period, indicating that contact with the case 10 has been removed,
the microprocessor 114 resets terminal 28 output pin one to an
"open" or "inactive current-sink" state. This embodiment therefore,
provides current-sink output for the duration that the electrical
switch's closed distal end cap 12 of the case 10 is pressed. Again,
the invention is not limited to the particular timer durational
increments mentioned above (two seconds and five-hundred
milliseconds). Other timer increments can easily be programmed into
the microprocessor 114 to alter the inventions sensitivity and
speed.
[0026] An alternative embodiment shown in FIG. 4 utilizes the
microprocessor 114 to alternate setting interface terminal 28 pin 1
to the "open" and "closed" states upon satisfaction of the two
conditions precedent described in detail above. The default state
is, therefore, unimportant. When the case 10 is touched as
described above, the microprocessor 114 initializes a two second
timer. If within the two seconds the piezo conditioning circuitry
18 sends a pressure signal as described above, the microprocessor
114 sets interface terminal 28 pin 3 to the "closed" or "active
current-sink" state for five hundred milliseconds and then resets
interface terminal 28 pin 3 to the "open" or "inactive
current-sink" state. At the same time, the microprocessor senses
whether interface terminal 28 pin 1 is in the "closed" or "open"
state and sets the output to the opposite state. In this
embodiment, therefore, the electrical switch's output current-sink
will toggle between active and inactive with each individual
contact with the closed distal end cap 12 of the case 10. The
invention is not limited to the two second timer duration mentioned
above. Other timer increments can easily be programmed into the
microprocessor 114 to alter the inventions sensitivity and
speed.
[0027] While the above are important features of the invention,
there are, of course additional features of the invention that will
form the subject matter of the claims appended hereto. In this
respect, it is to be understood that the invention is not limited
in its application to the details of construction and to the
arrangements of the components set forth in the previous
description or illustrated in the drawings. The invention is
capable of other embodiments and of being practiced and carried out
in various ways. Also it is to be understood that the phraseology
and terminology employed herein are for the purpose of description
and should not be regarded as limiting. As such, those skilled in
the art will appreciate that the conception, upon which the
disclosure is based, may readily be utilized as a basis for the
designing of other structures, methods, or systems for carrying out
the several purposes of the present invention. It is important,
therefore, that the claims be regarded as including such equivalent
constructions insofar as they do not depart from the spirit and
scope of the present invention.
[0028] The invention is illustrated with respect to specific
embodiments thereof. Though numerous characteristics and advantages
are set forth in the foregoing description, together with details
of the structure and function of the invention, the disclosure is
illustrative only. Changes may be made in detail, especially in
matters of materials, shape, size, and arrangement of parts within
the principles of the invention to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed. Various modifications and additions may be made and will
be apparent to those skilled in the art. Accordingly, the invention
should not be limited by the foregoing description in any manner,
but rather should be defined only by the following claims.
* * * * *