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Touch screens for HMI (human machine interface)
Dec 07, 2018


The touch screen panel according to the induction principle can be divided into four kinds of resistive, capacitive, surface acoustic wave touch, and optical. Resistive touch panel is mainly made of two sets of upper and lower ITO conductive laminate, using pressure conduction, the upper and lower electrode panel via the controller detect voltage changes and calculate the position of the point of contact input; capacitive touch panel is electrostatic coupling between the transparent electrode and the body of the arrangement arising from changes in the capacitance arising from induced current to detect its coordinates; principle of optical touch panel is calculated using the light source receiving interdiction principle, within the scope of the panel covered with light source and composition of the matrix and the receiver, when the light was interdiction support, you can not receive the signal receiver position, and to determine its precise location; the sonic touch panel is used, and calculated to emit ultrasonic reception strength to calibrate the relative position of contact with indicators was caused by absorption of ultrasound attenuation, the received signal has not action, the precise location via a controller and calculated based on the amount of attenuation before and after use.


Touch screen panel technology induction principle

Touch Description: When the touch of a finger Sensor, there will be an analog signal output by the controller converts the analog signal into digital signals that the computer can accept, and then via computer touch driver integration components are built, and finally by the display card output signal of the screen shows the touch position on the screen.

Touch technology according to the induction principle can be divided into: resistive touch panel (Resistive), capacitive touch panel (Capacitive), the optical touch panel (Optics), acoustic wave touch panel (Surface Acoustic Wave), electromagnetic touch panel.

A/D Controller: the most generic for the use of the USB or RS-232 port transmission controller, the controller function Sensor sent over an analog signal into a digital signal, via the driver to judge the use of the touch driver a variety of design and functionality increase can do various changes, for example, presents multiple language  convenience of customers, increase the handwriting recognition, multiple screen system support, computer game support, in addition to can increase the added value of the touch screen is still guest system software design in accordance with customer demand.


A resistive type touch screen panel

Resistive type touch panel is composed of ITO Film and ITO Glass middle separated by DOT, pass into the 5V voltage between ITO Film and ITO Glass, by finger or stylus to touch the ITO Film form a depression and lower ITO Glass contact voltage changes the digital signal via the A / D controller to let the computer do the arithmetic processing to obtain the (X, Y) axis position, thus achieving the purpose of positioning.

Resistance in accordance with the performance and universality can be divided into four-wire and five-wire, four-wire resistive line XY axis distribution in ITO Film and ITO Glass, will form an open circuit when the ITO Film severely scratched , caused by the touch panel inoperative. The five-wire regarded as four-wire touch panel improved the uniform electric field based on the ITO glass, the upper ITO Film purely as a conductor, so when the ITO Film was scratching only the Agency is unable to use other parts of the action can still , but if the injuries to the lower ITO Glass will still result in the failure of the Touch Panel.

Main actuation principle is easy to find on the Internet conductive layer by layer structure (structure diagram)

When a single finger, stylus or even other forces put pressure on the surface of the touch panel

Generating circuit conduction cause Duplex conductive layer contacts

After the back-end IC contact position can be calculated to achieve the effect of touch

Simple, as long as there is a slight pressure action on the reaction

NDSL is a representative


capacitive type touch screen panel

Capacitive type touch screen panel is substantially derived for improved scratch resistance type characteristics in the structure of the outermost layer of a thin layer of silica-hardened layer, hardness reaches 7H, second layer of ITO the establishment of a uniform electric field on the glass surface, sense the body of a weak current to achieve the purpose of touch, the lowest layer ITO acts as a masking function in order to maintain the Touch Panel can be good interference environment.

The action principle is to produce a uniform electric field at the surface of the touch panel

Single human contact will be changed because the human body is a conductor electric field

Detection of changes in the electric field to determine the touch location.

Capacitive panel to rely on the human body or something conductive to reach only response


Sonic touch screen panel

Sonic touch panel is developed In order to improve the shortcomings of the capacitive touch panel, capacitive touch panel susceptible to noise and static characteristics and surface hardening treatment to achieve 7H, but Sio2 in order not to cut off from the ITO surface currents, so the plating is very thin when applied to the capacitance of the external force is too large, there will still be a wound to the ITO may cause a malfunction, therefore, the development of a sound wave touch panel.

Sole by the glass composition on the surface of the acoustic wave touch panel, the three corners of the intermediate region is formed by a ultrasonic transmitter and receiver in a uniform acoustic force field, the use of sound waves encounter soft medium is absorbed energy Typical do contact control positioning the purpose of.


Optical (infrared) touch panel

Optical touch panel in recent years through the LED quality improvement and process sophisticated comeback, optical touch panel is composed by the the surrounding infrared emitter and receiver, the infrared rays generated by the X-axis and Y-axis to form a matrix arrangement, naturally when an opaque object blocking the light after the X-axis and Y-axis positioning.




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