For resistive screen, due to the use of processor is inside the ADC module (or an external ADC chip), change the type and size of replacement, as long as there isn't a large difference with the original plan, guarantee the working voltage smartboards in classrooms current can be used. But for complex such as multitouch, gesture recognition, etc., resistive screen obviously can't meet. For capacitance screen, because the I2C, must be through the USB communication interface, such as internal communication protocol designed by the original factory screen, then the whole drive affected point is very broad, mainly manifested in the following aspects:
The kernel version, communication protocol interface, driver USES the kernel of environment, the version of the driver. Kernel version changes, it will cause the kernel API changes, and thus drive shall not apply;
IC hardware upgrade could lead to a part of interactive whiteboards in the classroom the register values change.
Drive once modified, can the problem left to the production process, need to maintain multiple product firmware.
So select capacitance screen, more need to consider the overall supply chain and production control ability.
Overall, resistive screen is suitable for the complex industrial production environment or medical environment, field application to wear gloves or use other tools to press the point contact. And capacitance screen is more applicable to high-end, interactive flat panel display using partial consumer environment, multi-touch, achieve the function more complex applications.
The touch of industrial touch screen is using the working current of induction of human body. Industrial control touch screen is a four layer composite glass screen, the inner surface of the glass and laminated coated with a layer of ITO (indium tin oxide), the outermost layer is a thin layer of silica glass coating, laminated indium tin oxide coating as the working face, four corners raises four electrodes, lining the indium interactive boards for classrooms tin oxide shield to ensure good working environment.
According to the working principle of touch screen and transmission of information media, the touch screen is divided into four kinds, respectively is resistive, capacitive sensing type, infrared and surface acoustic wave. Has its own advantages and disadvantages of each kind of touch screen, and to understand what kind of touch screen is suitable for what kind of situation, the key is to understand the working principle and classroom interactive whiteboard characteristics of every kind of touch screen technology.
When the fingers on the metal layer, the electric field due to the human body, users and industrial touch screen surface formed by a coupling capacitance, for high frequency current, capacitance is directly conductor, so the fingers from the point of contact suck a small current. The current points out from the touch screen on the four corners of the electrode, the four electrodes and the current is proportional to the finger to the four corners, the controller based on the four current ratio of precise calculation, it is concluded that the location of the touch point.