Input interface device with semiconductor strain gage
View Patent ↗The invention provides for an interface device that measures strain on a specific area of the printed circuit board. The measurements are converted into an electrical signal and sent for processing. The processing results in the apparatus performing a desired function. The interface device includes a printed circuit board. The printed circuit board comprises a plurality of layers, including a conductive layer. The interface device further includes a strain sensing device. The strain sensing device is mounted on the printed circuit board and includes a substrate, a strain sensing element, and associated circuitry. In some instances, the strain sensing device includes one strain sensing element and in other instances multiple strain sensing elements can also be used. In one embodiment, the strain sensing device can include a piezoresistive strain gage combined with signal conditioning circuitry such that a single electronic component can be mounted on the printed circuit board for reduced cost and improved signal-to-noise performance. In operation, a user or another device applies force on the printed circuit board in the area of the strain sensing device. The strain sensitive element deforms in response to the applied force or strain on the printed circuit board. The deformation results in the change of resistance or conductivity of the strain sensitive element. The associated circuitry, which can be a signal conditioning circuit, converts the change in resistance or conductivity into a digital signal. Once the conversion occurs, the associated circuitry uses the conductive layer of the printed circuit board to communicate the digital signal to either the processor or the processing circuit of the electronic apparatus. The processor or processing circuit receives the digital signal and responds by performing a desired action. In one instance the interface device may be used to measure the magnitude of the force applied by a finger pressing on the touch screen of an electronic apparatus such as a cell phone. The magnitude of the applied force can then be used to control, the operation of the cell phone. A high magnitude force would result in a higher strain being sensed and can cause the apparatus to operate in one way, whereas a low magnitude force would result in a lower strain being sensed and can cause the apparatus to operate in another way, e.g., in a mobile phone environment where an application is used to draw a picture, a light force applied to the touch screen could be processed to result in a thin line being drawn and a stronger force could be processed to result in a wider line being drawn. In another instance the interface device may be used to measure the magnitude of the force applied to a control toggle on the steering wheel of a car. The toggle may be used to control the intensity of the sound emitted from the audio system in the car. A high magnitude force could be processed to cause the intensity of the sound to change rapidly whereas a low magnitude force could be processed to cause the intensity of the sound to change slowly.
1. An interface device for an electronic apparatus comprising:
a printed circuit board having a plurality of layers, wherein one or more of the layers is a conductive layer;
a strain sensing device comprising
a substrate, wherein the substrate is formed from a material which is not the same material as the printed circuit board,
at least one strain sensing element formed on the substrate, wherein the strain sensing device is mounted on the printed circuit board,
and a signal conditioning circuit formed on the substrate and connected to the strain sensing element,
wherein the strain sensing device measures the deformation or bending of the printed circuit board in response to an applied force or strain on the printed circuit board, wherein the deformation or bending results in the change of resistance or conductivity of the strain sensing element, wherein the amount of change of resistance or bending is translated into a digital signal; and
a processing unit communicatively connected to the printed circuit board and the strain sensing device, wherein the processing unit receives the digital signal thereby resulting in an action executed by the processing unit.
2. The interface device of claim 1 , wherein a flexure is formed within the printed circuit board, wherein the force is applied to the flexure, wherein the flexure includes a plurality of sides, wherein at least one side is attached to the printed circuit board thereby providing structural stability to the flexure, wherein a plurality of sides are not attached to the printed circuit board, wherein the flexure is situated such that either the top, bottom, or both top and bottom of the flexure is able to deform or bend when a force is applied.
3. The interface device of claim 2 , wherein the flexure has a length of between 2 mm and 10 mm, wherein the printed circuit board has a thickness of between 0.2 mm and 2 mm and wherein the flexure is designed to have a maximum strain of between 10 and 1000 microstrain when a force of between 0.1 and 10 N is applied to the flexure.
4. The interface device of claim 1 , further comprising a signal conditioning circuit, wherein the signal conditioning circuit is formed on the substrate of the strain sensing device, wherein the signal conditioning circuit converts the change of resistance or conductivity of the strain sensing element into the digital signal.
5. The interface device of claim 4 , wherein the signal conditioning circuit communicates with the processing unit to relay the digital signal.
6. The interface device of claim 4 , wherein the conductive layer of the printed circuit board is used for communicating with the processing unit through the signal conditioning circuit.
7. The interface device of claim 1 , wherein the processing unit is a processor or processing circuit.
8. The interface device of claim 1 , wherein the strain sensing element is a semiconductor strain gage.
9. The interface device of claim 1 , where substrate of the strain sensing device is attached to the printed circuit board with an epoxy.
10. The interface device of claim 1 , wherein the substrate of the strain sensing device is attached to the printed circuit board with solder.
11. The interface device of claim 10 , wherein the solder includes a filler material.
12. The interface device of claim 1 , wherein the strain sensing device includes a plurality of bond pads.
13. The interface device of claim 12 , wherein the plurality of bonds pads define the outline of two or more regions, wherein a region contains either a strain gage or a signal conditioning circuit.
14. The interface device of claim 1 , wherein the substrate of the strain sensing device is mounted in a recess in the printed circuit board.
15. The interface device of claim 1 , wherein the action executed by the processing unit is either to turn a switch to an ON or an OFF position for a desired feature of the electronic apparatus.
16. A method of sensing a force applied to a printed circuit board of an electronic apparatus, the method comprising:
exerting a force on a printed circuit board thereby resulting in the bending or deforming of the printed circuit board; wherein the magnitude of force exerted is directly related to the amount of deformation such that a force with a smaller magnitude results in a smaller deformation and a force with a larger magnitude results in a larger deformation;
measuring the bending or deformation of the printed circuit board using a strain sensing device, wherein the strain sensing device comprises
a substrate, wherein the substrate is formed from a material which is not the same material as the printed circuit board,
at least one strain sensing element formed on the substrate, wherein the strain sensing device is mounted on the printed circuit board,
and a signal conditioning circuit formed on the substrate and connected to the strain sensing element;
changing the resistance or conductivity of the strain sensing device, wherein the change in resistance of conductivity is in response to a force applied on the printed circuit board;
converting the change into an analog signal using a signal conditioning circuit that is coupled to the strain gage; and
converting the analog signal into a digital signal using the signal conditioning circuit; and
communicating the digital signal to a processing unit that is communicatively coupled to the strain gage such that the processing unit receives the digital signal and executes an action.
17. The method of claim 16 , wherein a smaller force results in the processing unit to execute a first action for the electronic apparatus while a larger force results in the processing unit to execute a second action for the electronic apparatus.
18. The method of claim 17 , wherein the first action and the second action activate the same feature of the electronic apparatus, wherein the first action provides a slower or lesser response while the second action provides a faster or higher response.
19. The method of claim 16 , the force exerted on the printed circuit board is on a flexure, wherein a flexure is formed within the printed circuit board, wherein the flexure includes a plurality of sides, wherein at least one side is attached to the printed circuit board thereby providing structural stability to the flexure, wherein a plurality of sides are not attached to the printed circuit board, wherein the flexure is situated such that either the top, bottom, or both top and bottom of the flexure is able to deform or bend when a force is applied.
20. The method of claim 19 , wherein the force exerted results in the bending of the flexure.
21. The method of claim 16 , wherein the amount of bending of the printed circuit board is reduced by applying an epoxy or solder to the substrate that is mounted on the printed circuit board.