2.4 MSP CapTIvate PCB Design Guidelines for Self Capacitive Sensors
A good capacitive sensor design can improve a product's HMI (human machine interface) performance and robustness. This video introduces the fundamentals of self capacitance as well as suggested guidelines for button, slider and wheel sensor PCB layout.
This video covers self capacitive:
- PCB layout principles
- Button sensor
- Slider and wheel sensors
Capacitive sensing is performing a measurement to detect a capacitive change to a sensor element. A sensor element can be any conductive material (copper PCB plane, a wire, etc.) The change can be due to human interaction, such as a finger, ear, or hand. This is often termed "capacitive touch" or "proximity." However, capacitive sensing is not limited to human interaction. Other objects or materials can change the capacitance of a sensor. This could be an organic or inorganic material. Think metals or liquids. In either case, the interpretation of the change in capacitance is what defines an application.
Measuring changes in capacitance with respect to earth ground is commonly referred to as self capacitance measurement. Sometimes it is also referred to as surface capacitance. In a parallel-plate model, the electrode defines one plate of the capacitor, with the other plate being ground (for C_electrode) or the user's finger (for C_touch). A touch causes the capacitance of the electrode to increase. (Typically 1-10pF)