Application of capacitive sensing technology in control circuits for video games

　　Graphics and processing speed can limit or showcase the development status of software in games, making them most likely to attract attention from consumers and critics. The console controller is equally important. The interface methods of video game controllers are constantly being updated, aiming to enable more effective interaction with the scenes displayed on the screen.

　　Although most video game development focuses on software and processors, many major creative and forward-thinking ideas are related to controllers. Because game systems and peripheral developers strive to improve how players interact with their systems, continuous development and improvements are made in ergonomics, style, functionality, and unique features.

　　Seeking new models

　　We may all remember the earliest Atari controllers with square bases, featuring a central joyckey and a button beside it—a design that was quite sufficient for video games at the time. At that time, all you needed were basic directional controls and a select button to play games, and this controller fully met those requirements. Nintendo later released the Nintendo Entertainment System with a square controller, where the arrow button replaced the game stick and added a second button—a major change developed with existing technology.

　　From that point on, the controller became increasingly complex. Now, standard console controllers have more buttons than ever before, and each key offers more powerful functions. Buttons with pressure-sensitive interruption provide better control over the trigger effect, which is especially useful for braking and acceleration control in driving video games.

　　In fighting games, capacitor-to-voltage converters use switching capacitor technology. The rumble-packs feature allows players to experience realistic sensations, rather than just sound and light effects. Thanks to the joystick's outstanding simulation capabilities, it comes to life on the latest controllers. Capacitive sensing technology (capacitive touch sensing) is the latest interface technology that enhances the usability of game controllers and offers the most impressive mechanical designs.

　　Overview of Capacitive Sensing Technology

　　Capacitive sensors are most commonly used on personal computer touchpads and portable media players. Mobile phone manufacturers have also begun investing to promote its use and have developed several models for sale. Simple architecture, device waterproofing, and robust mechanical design are all highly attractive features of capacitive sensing interfaces.

　　Method

　　There are several ways to achieve capacitive sensing effects, but the basic elements remain fixed. Among them, capacitive sensors are simply copper pads connected to the controller circuit on a printed circuit board. The combination of sensing buttons and their connecting wires generates capacitance around them.

　　The grounding plane, metal support devices, and other electronic and mechanical components considered during design all affect the sensor's capacitance value. It is generally believed that the sensor's capacitance value is equivalent to the capacitance value between it and the ground plane. When a conductive trigger material (such as a finger) approaches the sensor to a certain extent, the capacitance value increases. This is because the conductor itself creates more possible paths between the sensor and the ground plane, and the more paths there are, the more field lines are generated, which in turn increases the overall capacitance value.

　　At the front end of a capacitive sensor, there are switched capacitors, an internal current source, or a voltage source with external resistors. These methods are all intended to input voltage values into the sensing capacitor. This voltage value can be processed by the ADC or a charging time measurement circuit composed of comparators, and then transmitted to the counter or timer. When digital output values are used for data processing and decision-making in capacitive sensing systems, they undergo transformations in the ADC output value or analog changes in the count value in the capacitor. Later, we will delve into two commonly used methods: relaxation oscillator and successive approximation method.

　　Actual design

　　Building a capacitive sensor in actual design is not difficult. As mentioned above, capacitive sensors simply place a conductor sheet on the printed circuit board, usually a copper sheet. This conductor sheet is triggered by a material—usually a finger—and can be directly connected to the control components; And you can interact directly with it. The induction plate is placed on an overlay surface directly below the sensing area. It is best to ensure there is no air between the sensor and the overlay, and a non-conductive adhesive should be used to tightly adhere the sensor substrate to the overlay.

　　The control circuit can be set near the sensor, and the closer the better. The mechanical structural requirements of sensors determine the configuration of control circuits. The farther the sensor and the control circuit, the higher the primary capacitance between the sensor and the ground plane, because the conductor interacts with the surrounding environment and thus increases the capacitance; The longer the distance, the more pronounced the increment.

　　Although it's not easy to set the maximum distance, generally speaking, 6 to 12 inches is considered the functional limit. The substrate of capacitive induction devices is not fixed; Among these, the most common design is the basic FR4 printed circuit board with copper wires. In addition, elastic printed circuit boards with copper sheets (usually using polyimamide film—Kapton) are also common. Elastic substrates make mechanical design easier, especially on curved surfaces. Printed with conductive ink such as carbon or silver on elastic materials, capacitive sensors can be produced at extremely low cost, but this process requires control of the PCB and connectors because the elastic material cannot be soldered.

　　Transparent conductive materials, such as Indium TinOxide (Indium TinOxide; ITO has also been rapidly and widely used in touchscreen applications. ITO sensors are printed onto glass or polyethylene terephthalate (PET) films, then combined with the final finished design. Although chip-on-glass is now available to control such applications, using elastic connectors or hot bar soldering on printed circuit boards is a more economical approach.