Embodiments of the invention relate generally to proportional push buttons and, more particularly, to a strain gauge proportional push button.
Remote controls for controlling machinery or devices by radio frequency generally consist of a remote hand-held transmitter which can be a push button panel, a console, or other type of transmitter according to the application, where said transmitter is partly managed by an operator, through which said operator can remotely provide instructions to the machine or device. The transmitters may incorporate a plurality of mechanisms—including push buttons, rotary buttons, selector switches, joysticks or levers—each of which has a different function. As an example, a transmitter for use with an off-road vehicle or equipment may incorporate a plurality of mechanisms to control a crane, winch, etc. on the vehicle/equipment.
With respect to push buttons included on the remote control, it is recognized that such push buttons may be in the form of proportional pushbuttons that generate a range of values depending on how hard the push button is pressed. This allows an operator to, for example, increase the speed of the controlled axis on the equipment (e.g., crane) by pressing harder on the push button. Most proportional push buttons on remote control transmitters have a long range of travel, such as greater than ½″, for example. For proportional push buttons that are included as part of a remote transmitter, the buttons are sealed and protected from the environment—with a flexible rubber seal typically providing protection for the push button over its range of travel.
While long range proportional push buttons as described above are effective for controlling their associated machinery/device, it is recognized that the standard construction of these buttons has drawbacks and limitations associated therewith. For example, as the rubber seal of a long range push button is required to flex long distances, the rate of wear of the seal (and the switch in general) is increased. Additionally, the long range push button and its seal have to be physically larger for mechanical strength and flexibility, such that the size/footprint of the button on the remote control is increased. Further, it is more costly to create a mechanically robust push button that has a longer range of travel.
It would therefore be desirable to provide a proportional push button that overcomes the aforementioned drawbacks of increased wear, size and cost associated with existing long range proportional push buttons.
Embodiments of the invention are directed to a strain gauge proportional push button for use in a transmitter device.
According to an aspect of the invention, a transmitter device includes a printed circuit board including one or more electrical components thereon and a proportional push button having a flexible membrane, a dome switch positioned beneath the flexible membrane and attached to the printed circuit board, the dome switch being proximate to the flexible membrane such that depression of the flexible membrane causes the dome switch to snap down and thereby form a closed circuit in the dome switch, and a strain gauge formed on or applied to the printed circuit board and positioned adjacent the dome switch, the strain gauge generating an electrical output proportional to an amount of deflection of the printed circuit board caused by pressure exerted thereon by depression of the flexible membrane and the dome switch.
According to another aspect of the invention, a proportional push button for use on a transmitter device includes a flexible button membrane and a snap-action dome switch positioned beneath the flexible membrane and attached to a printed circuit board, the snap-action dome switch being proximate to the flexible membrane such that depression of the flexible membrane causes the a movable member of the snap-action dome switch to collapse and thereby form a closed circuit in the dome switch. The proportional push button also includes a strain gauge structure formed on or applied to the printed circuit board and positioned adjacent the dome switch, the strain gauge structure generating an electrical output proportional to an amount of deflection of the printed circuit board, with the deflection of the printed circuit board being caused by pressure exerted thereon by depression of the flexible membrane and the snap-action dome switch.
According to yet another aspect of the invention, a transmitter device includes a printed circuit board and a plurality of proportional push buttons positioned on and adjacent to the printed circuit board. Each of the plurality of proportional push buttons further includes a flexible membrane, a dome switch positioned beneath the flexible membrane and attached to the printed circuit board proximate to the flexible membrane such that depression of the flexible membrane causes the dome switch to snap down and thereby form a closed circuit in the dome switch, and a strain gauge structure positioned adjacent the dome switch and configured to generate an electrical output proportional to an amount of deflection of the printed circuit board caused by pressure exerted thereon by depression of the flexible membrane and the dome switch. The strain gauge structure further includes an arrangement of strain gauge resistors and push button monitoring circuitry in operable communication with the arrangement of strain gauge resistors to process electrical output therefrom. The printed circuit board includes an arrangement of slots formed therein adjacent each strain gauge structure, with each arrangement of slots at least partially surrounding the arrangement of strain gauge resistors of a respective strain gauge structure to isolate the strain gauge structure from a strain gauge structure of any adjacent proportional push buttons.
Various other features and advantages of the present invention will be made apparent from the following detailed description and the drawings.
The drawings illustrate preferred embodiments presently contemplated for carrying out the invention.
In the drawings:
Embodiments of the invention are directed to a strain gauge proportional push button. The proportional push button includes a dome switch mounted on a printed circuit, with a strain gauge being provided on the printed circuit that measures the force applied to the circuit board.
While embodiments of the invention are described below as being implemented in a remote hand-held transmitter device (i.e., a “remote control”) used to control machinery or devices, it is recognized that strain gauge proportional push buttons could be employed on numerous other systems or devices. Accordingly, embodiments of the invention should be understood to not be limited to the specific implementations and embodiments described herein, and it is recognized that other systems or devices that employ strain gauge proportional push buttons are considered to be within the scope of the invention.
Referring to
The remote control 10 also includes components 18 that are mounted on a printed circuit board 20 positioned within the outer housing. The printed circuit board 20 may be formed of one or more layers of dielectric material and one or more layers of metal traces (not shown) and may be a rigid printed circuit board or a flexible printed circuit board. Components 18 may be, for example, integrated circuits, discrete components such as capacitors, resistors, and inductors, switches, connectors, sensors, RF transmitters, input-output devices such as status indicators lights, audio components, or other electrical and/or mechanical components for the remote control 10. Components 18 may be attached to printed circuit board 20 using solder, welds, anisotropic conductive film or other conductive adhesives, or other conductive connections. One or more layers of patterned metal interconnects (i.e., copper traces or metal traces formed from other materials) may be formed within one or more dielectric layers in printed circuit board 20 to form signal lines that route signals between components 18.
As shown in
An exemplary construction of the dome switch 24 is illustrated in
Referring back now to
An illustrative strain gauge resistor configuration that may be used for strain gauge 42 is shown in
Illustrative push button monitoring circuitry 50 that may be used in making strain gauge measurements for strain gauge 42 of push button 16 is shown in
Push button monitoring circuitry 50 may include an amplifier 51, an analog-to-digital (A/D) converter 52 and processing circuitry 54—with processing circuitry being in the form of a microprocessor running software that interprets the A/D converter output. In an exemplary embodiment, auto-zeroing circuitry 55 is also included in push button monitoring circuitry 50 that performs an auto-zeroing of the applied force to the push button 16, as will be explained in greater detail below. While auto-zeroing circuitry 55 is shown in
During operation of push button monitoring circuitry 50, a voltage drop of Vcc-Vss will be applied across bridge circuit 56. Resistors R1, R2, R3, and R4 may all nominally have the same resistance value (as an example). In this configuration, bridge circuit 56 will serve as a voltage divider that nominally provides each of paths 58 and 60 with a voltage of (Vcc−Vss)/2. The voltage difference across nodes N1 and N2 will therefore initially be zero.
With one suitable arrangement, resistors R1 and R3 are mounted in a flexible printed circuit 20 so that both resistors R1 and R3 will experience similar stresses during use. Resistors R2 and R4 may be located away from resistors R1 and R3 and/or may be oriented so as to avoid being stressed while resistors R1 and R3 are being stressed. This allows resistors R2 and R4 to serve as reference resistors. With this approach, pressure to the strain gauge resistors R1 and R3 in flexible printed circuit 20 from a user finger will cause the resistance of resistors R1 and R3 to rise simultaneously while resistors R2 and R4 serve as nominally fixed reference resistors (compensating for drift, temperature changes, etc.). Because both R1 and R3 respond to the application of pressure, amplifier 51 and analog-to-digital converter 52 will receive a larger signal than a configuration in which only one of the strain gauge resistors in bridge circuit 56 response to the application of pressure. This is because the voltage on path 58 will drop due to the increase in the resistance of resistor R1 while the voltage on path 60 simultaneously rises due to the increase in the resistance of resistor R3. Other types of bridge circuit layouts may be used if desired.
Due to the changes in resistance to resistors R1 and R3, the voltage between paths 58 and 60 will vary in proportion to the strain that is being applied to the strain gauge structure 42. Amplifier 51 amplifies the voltage signal across paths 58 and 60, while analog-to-digital converter 52 digitizes the amplified voltage signal and provides corresponding digital strain (stress) data to processing circuitry 54. Processing circuitry 54 and other control circuitry in remote control 10 can take appropriate action in response to the measured strain data. For example, processing circuitry 54 can convert raw strain data into button press data or other button input information. Remote control 10 can then respond accordingly to generate a desired signal/output (e.g., by using the strain gauge button data as data for generating an RF control signal for transmission to a remotely controlled device/machine, etc.).
As indicated above, the strain gauge 42 (or more accurately resistors 44) may be formed in/on the printed circuit board 20 or attached thereto. In an embodiment where the strain gauge resistors 44 are attached to the printed circuit board 20, the strain gauge resistors 44 may be applied using traditional techniques. In an embodiment where the strain gauge resistors 44 are formed in/on the printed circuit board 20, the resistors 44 can be printed directly on the printed circuit board 20 or formed as part of a layer within the circuit board—with the integral forming of the strain gauge resistors 44 with the printed circuit board 20 conserving space within the remote control 10 and improving performance and reducing complexity thereof. When the strain gauge resistors 44 are formed integrally with the printed circuit board 20, the printed circuit board may be formed of multiple layers of material, as illustrated in
In operation of the remote control 10, and of the proportional push button 16 thereon, an operator depresses upper flexible membrane 22 such that it comes in contact with the dome switch 24 and causes a deformation or snapping down of the dome switch 24. The snapping down of the dome switch 24 closes the circuit in the push button 16 and causes an electrical signal to be generated (via the dome member 26 coming in contact with the electrical contacts/traces 30, 34 to provide an electrical connection, as in
When the circuit is closed responsive to the dome switch 24 being snapped down/closed, an auto-zeroing of the applied force to the push button 16 is initiated by auto-zeroing circuitry 55—with the dome switch 24 being in operable communication with the auto-zeroing circuitry 55 to enable such auto-zeroing (e.g., wired to the auto-zeroing circuitry 55, either as separate circuitry or incorporated in processing circuitry 54). The auto-zeroing step is performed by comparing a known amount of force required to collapse to the dome switch 24 to the actual force applied to the dome switch 24 to collapse the dome switch 24 in the present depression of the push button 16. The difference between these force values can then be determined to perform the auto-zeroing. Beneficially, the auto-zeroing allows for changes in the resistive elements 44 of strain gauge 42 that might be due to temperature and other environmental factors to be to be accounted for and nulled out of the force equation employed with the strain gauge 42 in determining the force applied thereto, such that the proportional output of the remote control 10 is then determined by how much force the operator continues to apply to the push button 16. For force that is continued to be applied to the push button 16 (to upper flexible membrane 22 and dome switch 24), stress/bending imparted to the printed circuit board 20 is measured by strain gauge 42—with a change in resistance within the stain gauge resistors 44 being measured using strain gauge resistor monitoring circuitry 50, as shown and described in
In an exemplary embodiment, in generating a proportional output via push button 16, a maximum proportional value can be determined by having the operator calibrate the maximum amount of force he is willing to apply to the push button 16. This maximum force is measured and stored permanently in the remote control 10 (e.g., in processing circuitry 54) during the calibration process. It is then used to scale the proportional output based on these calibrated values.
While the remote control 10 of
In order to minimize the force interactions from one push button 16 to another push button 16 during operation of the remote control 70, an exemplary embodiment of the remote control 70 includes a printed circuit board 20 having a plurality of slots or cutouts 72 formed therein adjacent each of the push buttons 16. As shown in
Referring now to
Beneficially, embodiments of the invention thus provide a strain gauge proportional push button that overcomes the drawbacks of increased wear, size and cost associated with existing long range proportional push buttons. The strain gauge proportional push button makes use of a snap-action dome button/switch and strain gauge sensor to enable detection of when the push button is actuated on and a detection of further force/pressure subsequent to activation of the switch. An auto-zeroing feature of the push button beneficially allows for changes in resistive elements of strain gauge that might be due to temperature and other environmental factors to be to be accounted for and nulled out prior to stress/strain detection.
Therefore, according to an embodiment of the invention, a transmitter device includes a printed circuit board including one or more electrical components thereon and a proportional push button having a flexible membrane, a dome switch positioned beneath the flexible membrane and attached to the printed circuit board, the dome switch being proximate to the flexible membrane such that depression of the flexible membrane causes the dome switch to snap down and thereby form a closed circuit in the dome switch, and a strain gauge formed on or applied to the printed circuit board and positioned adjacent the dome switch, the strain gauge generating an electrical output proportional to an amount of deflection of the printed circuit board caused by pressure exerted thereon by depression of the flexible membrane and the dome switch.
According to another embodiment of the invention, a proportional push button for use on a transmitter device includes a flexible button membrane and a snap-action dome switch positioned beneath the flexible membrane and attached to a printed circuit board, the snap-action dome switch being proximate to the flexible membrane such that depression of the flexible membrane causes the a movable member of the snap-action dome switch to collapse and thereby form a closed circuit in the dome switch. The proportional push button also includes a strain gauge structure formed on or applied to the printed circuit board and positioned adjacent the dome switch, the strain gauge structure generating an electrical output proportional to an amount of deflection of the printed circuit board, with the deflection of the printed circuit board being caused by pressure exerted thereon by depression of the flexible membrane and the snap-action dome switch.
According to yet another embodiment of the invention, a transmitter device includes a printed circuit board and a plurality of proportional push buttons positioned on and adjacent to the printed circuit board. Each of the plurality of proportional push buttons further includes a flexible membrane, a dome switch positioned beneath the flexible membrane and attached to the printed circuit board proximate to the flexible membrane such that depression of the flexible membrane causes the dome switch to snap down and thereby form a closed circuit in the dome switch, and a strain gauge structure positioned adjacent the dome switch and configured to generate an electrical output proportional to an amount of deflection of the printed circuit board caused by pressure exerted thereon by depression of the flexible membrane and the dome switch. The strain gauge structure further includes an arrangement of strain gauge resistors and push button monitoring circuitry in operable communication with the arrangement of strain gauge resistors to process electrical output therefrom. The printed circuit board includes an arrangement of slots formed therein adjacent each strain gauge structure, with each arrangement of slots at least partially surrounding the arrangement of strain gauge resistors of a respective strain gauge structure to isolate the strain gauge structure from a strain gauge structure of any adjacent proportional push buttons.
Embodiments of the present invention have been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.