The article introduced a kind of many pushbutton to help the design example of an aluminous face plate, this face plate is common mix at electric home appliances<gj consume kind of electron product. This kind of method also can apply at other data, be like stainless steel or metallic alloy. It provides the guidance that designs about mechanical system and sensor, the measurement that includes whole system give a demonstration function result.

  

The inductance formula that is used at touching metallic button passes feeling technology 

 

Inductance type passes feeling technology can basis communication (AC) the change of magnetic field is measured with the metal approach level. The AC electricity generation that flows in inductor is perpendicular the AC magnetic field at electric current. LDC measures the AC magnetic field that enters sensor when electric target around when the inductance deflection of the induction coil of generation. The essence when metrical inductance deflection can be used at sensor coil is close to in the target defines a goal.

 

 In system of inductive type ToM (graph 1) in, sensor coil is located in every pushbutton lower part. The metal presses the temporary deflexion that can bring about micron apparently gently. Although cannot see or find this kind of change (feedback besides the touch that offers intentionally) , but high resolution LDC detects very easily. Next, this incident is pressed for small controller by the explanation the pushbutton in the system.

 

Graph 1: Feel the systematic block diagram that the metal realizes

 

Systematic requirement 

 

Stem from the purpose that discusses originally, electric home appliances<gj of give typical examples has the ToM Control Panel that contains pushbutton of two photographs adjacent, the diameter of every pushbutton is 20mm, removed 26mm (the center reachs a center) . Face plate surface is the compressed aluminium with a 0.8 thick millimeter board, milling of every pushbutton lower part comes 0.25 millimeter are thick. Frequency subsystem needs sound feedback, this subsystem already in consist in system, so that be in,press be indicated to the user when pushbutton.

 Optimal result is achieved when passing feeling technology system to designing inductance form, need consideration designs a category 3 kinds below:

 

1. mechanical system is designed

 

Understanding affects the crucial factor that the system answers, for example the amount of pushbutton, size and decorate, and sensor span and the optimal target that install a technology.

 

2. sensor designs a system

 

Practice of optimal sensor design and proper coil geometry form ensure LDC can detect microcosmic metal deflexion.

 

3. software algorithm and user feedback

 

Data processing and check calculate a law to be used at pressing the time of pushbutton is mixed certainly strength.

 

Mechanical system is designed

 

Graph the pushbutton of 2 two photographs adjacent in showing this give typical examples uses a program.

 

Graph 2: Pushbutton of use photograph adjacent

 

Bring to bear on when slight force when pushbutton A, sheet metal is in parcel front printed circuit in pushbutton A board (PCB) sensor deflexion. Press by pushbutton press the deflexion amount that cause to answer enough big, showing frequency deflection mediumly in order to cause LC sensor, its can be detected by LDC and handle by algorithm. The potential error source of deflexion of pushbutton of adjacent of such as photograph or and so on of other environment noise can mask a needed response. Accordingly, pushbutton detects the place of incident needs deflexion quantity to should arise 10 times bigger than systematic noise answer, in order to ensure check calculates the surplus of the law. For example, if systematic noise shows,move for ±0.5μm, criterion pushbutton need is mobile at least 5μm ability detects easily.

 

A lot of elements can affect pushbutton to press the metallic deflexion amount that controls generation, for example metallic stuff and ply. Adopt good systematic design, the metallic deflexion of typical pushbutton is 20-50μm about.

  

1. designs natural pushbutton force 

 

Offer inside the typical and mechanical pushbutton that buy touch feedbacks, the touch in consuming electronic product or electric home appliances<gj for example feedbacks, need 2 N arrives the force of 5 N. To be not the pushbutton of shift component, the lesser force between 0.5N of consumer nature expectation and 2N. Bring to bear on to be in certainly the plate when the force of expectation is out of shape how many, need considers metallic class status, ply and pushbutton structure.

 With use larger plank bearing to compare, use smaller plate to be able to be in given the generation below force is larger be out of shape (graph 3) . For example, the aluminium that the power that needs 0.2N makes 0.25mm thick board be out of shape temporarily 5μm. 0.5mm board the equivalent power that large place needs is 1.5N.

 

Graph 3: Al-6061-T6 give typical examples board force and average deviation

 

Material chooses to be able to show an influence to realize proper deflexion to measure the volume of needs power, although the metallic ply of two kinds of material is identical. Different material can pass their Yang model quantity to undertake comparative, yang model measures the measurement that is metallic flexibility, with Pascal (Pa) measure for the unit. Have inferior the material that Yang model measures normally more agile. Aluminous (AL6061-T6) Yang model quantity is 68.9 GPa, and stainless steel (SS304) Yang model volume is higher, for 203 GPa, this makes its flexibility 3 times lower than aluminium. Aluminium is inductance type passes the good stuff alternative of feeling, because it can be neatly already on inductance type coil,generation tall inductance changes. The material of such as SS304 provided dovish result, but to given deflexion may need greater power.

 

What SS304 has 203 GPa is taller Yang model quantity, this makes its flexibility 3 times lower than aluminium. Aluminium is inductance type passes the good stuff alternative of feeling, because it can be neatly already on inductance type coil,generation tall inductance changes. Material provides dovish result like SS304, but to given deflexion may need greater power. What the deviation difference that pressure amount gives between two kinds of material shows a picture as follows 4.

 

Graph 4: The force of different material and average deviation

 

Normally, need bigger deflexion, because it offerred bigger inductance deflection for LDC sensor.

  

2. looks gauge length leaves 

 

Between sensor and metal nominal the distance must be pressed in the user pressure with producing the difficulty of apparent inductance deflection the respect is having main effect. Be close to sensor as metallic target, inductance deflection measures mushroom. Accordingly, optimal target distance is the position that sensor sensitivity is in peak value, but still have deflexion space. Still have the space of metallic deflexion to the consideration makes common difference and ensure, carry metal and sensor please between nominal span is more than 0.2 Mm. Can cave through be being founded in the metal in pushbutton lower part area will realize this kind of span, the small spacer that perhaps has cut through be being used between metal and PCB sensor will allow metallic deflexion. In addition, sensitivity drops quickly the 20 ％ ; that exceeds coil diameter because this, graph 5) .

 

Graph 5: Optimal target is apart from

  

3. machinery is kept apart 

 

When many pushbutton exist in the system, likelihood happening is different between pushbutton what do not expect is alternant. For example, should press when pushbutton A, abut metallic surface may be out of shape with such means, produce many shift on the pushbutton B sensor of photograph adjacent namely, and the likelihood is behaved for the blame of pushbutton B expectant pushbutton is pressed pressure. In press actively during pressing, 3 these principles can help reduce the machinery between photograph adjacent pushbutton to string together faze:

 

Ensure the physical deflexion that books pushbutton is bigger. From the point of electric angle, right button presses detect with what do not need the big letter a confusion of voices between is compared (SNR) it is to detect right button presses the simplest method of incident. Use thinner metal or choice to have low the material that Yang model measures can ensure the metal is easier be out of shape and smaller to the influence of photograph adjacent pushbutton. For example, aluminium is withier than a lot of stainless steel alloy.

 

Add a space or groove increases between photograph adjacent pushbutton ameliorable mechanical segregation. To achieve optimal result, it is pushbutton the coil that is more than a diameter to the span setting of pushbutton please.

 

The structure between pivot point supports pushbutton or construction the metal that can make pushbutton go up is out of shape stronger (graph 2) .