Nowadays, touch sensing technology is getting more and more attention and application in electronic products. It is not only beautiful and durable, but also has greater sensitivity, stability and reliability than traditional mechanical buttons, and can greatly improve the quality of products. Touch-sensing solutions are attracting more and more attention from IC design manufacturers. New technologies and ICs are constantly available, and domestic companies are launching similar programs. Cpress's CapSenseTM technology is a pioneer in sensing technology and is at the forefront of this field. It is widely used in high-end products. MCP has introduced mTouchTM, AT has also introduced QTouchTM technology, and FSL has introduced electric field sensing. The inductive touch of technology and MCP is also unique, and even ST has QST products.
However, all current touch solutions use dedicated ICs, which is costly and difficult to develop. The RC acquisition-based solution described in this article can be implemented on any MCU and is a revolutionary breakthrough in touch sensing technology. Firstly, the basic principle of RC charging, as well as the testing and improvement methods of charging time are introduced. Then, the hardware and software design steps based on STM8S single-chip microcomputer are discussed in detail, and the key points are noted.
Basic principle of RC charge detection
The basic principle of RC charge detection is to measure the charge and discharge time of an electrode capacitor using a PCB, and to detect whether there is a 'press' action by comparing small changes generated during human contact, and can be used for any single or multiple buttons. , roller, slider.
As shown in Fig. 1(a), the periodic charging voltage Vin is applied to the RC network, and Vout is measured to obtain the timing as shown in (b). By detecting the change in the time tc from the start of charging to the time when Vout reaches a certain threshold value, Determine if there is human contact. Figure 2 shows that the charging time becomes longer when there is human contact.
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Many people do not know what kind of cameras are invisible cameras, and do not know how to distinguish invisible cameras, so here is how to distinguish invisible cameras.
Invisibility, as the name suggests, means that it is not easy to be seen or found, so where do such cameras exist? In fact, invisible things are hidden by the external environment, so they will not be discovered. Such invisible cameras are generally hidden in things that are more difficult to see, such as: inside the socket, inside the TV, inside the stereo, inside the fan, etc. Cameras can be hidden in various household appliances. Why should they be hidden in electrical equipment? The main reason is that these equipments have power supply and will not be used because the camera cannot be powered.
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