What are the characteristics and application scope of the finger spring

Touch induction spring can be seen everywhere in everyday life. Touch induction spring refers to the special spring key used for capacitive and microcontroller touch screen appliances. Touch spring is also known as touch induction spring, key spring, contact spring. Its stainless steel wire and other materials include, piano carbon steel wire, low carbon steel wire, high carbon steel, manganese steel wire, nickel wire, 60SizMNA, environmental protection nickel, nickel plating free white K, straight gold, gold, silver, bronze, ancient silver and so on. Touch spring refers to the special spring key used for capacitive and microcontroller touch screen appliances. Touch spring can also be called touch induction spring, key spring, contact spring. For the traditional mechanical switch, it is a robust capacitive induction replacement scheme. It does not need to change the shell mold to realize the touch key to control the product, and the sensitivity of the touch is also very good.

First, the range of use of the finger spring

Because touch refers to the sensitivity of the spring is very good, so the applicability is wide and in everyday life we see contact spring products have induction cooker, light wave stove, electric, disinfection cabinet, lampblack machine, water heater, fan, warm wash dish machine, paper, massager, electric oven, electronic wine ark, water dispenser and a series of high-grade intelligent touch refers to the small home appliance products.

Touch refers to the spring

Two, the working principle of the finger spring

1. The use of spring to build capacitive inductor electric-capacitive induction is a robust alternative to the traditional mechanical switch. However, in some applications, the printed circuit board cannot be placed directly under the overlay or attached to the device housing. Applications include household appliances such as cookstoves, washing machines, refrigerators, microwave ovens, and a variety of vehicle electronics such as radio and TV tuners, control panels, occupant detection systems on seats, metal spring sensors - which can be used instead of solid-state conductance sensors so that the PCB can be positioned away from the cover, And can provide reliable sensor connection under the working conditions of strong vibration or rapid temperature change. In addition, the spring can also provide backlighting, fusion mechanical and capacitive buttons and other functions.

2. In order to determine the optimal physical size of the spring, the correlation of the FTC will be modeled according to its height, diameter and the thickness of the spring wire. When the finger is placed on the sensor, the spring is as sensitive as the solid-state conductance sensor. The sensitivity of both sensors decreased when the finger position was slightly away from the center of the sensor, but the sensitivity of the spring sensor was slightly stronger than that of the conductance sensor. When the finger position is deviated, the strong signal on the spring sensor is a big advantage of the spring sensor, especially in the application of slider), this advantage is more obvious. If the cover is 2 mm thick or thicker, the spring sensor will be more sensitive. More suitable for the best capacitance characteristics of the spring physical size.

3. The height of the finger spring should be 5 mm or above. Beyond this range, the sensitivity will no longer increase with the height of the spring, but will not lead to performance degradation; Thus, the distance between the board and the overlay can be lengthened accordingly as needed. If the height of the spring is less than 5 mm, characteristics such as elasticity, sensitivity and side sensitivity are affected. For 4 mm thick cover, the diameter of the spring must not be less than 10 mm for optimal spring sensitivity. In certain cases, a spring with a smaller diameter may be selected if the sensitivity of the spring is sufficient in relation to the selected cover. When the FTC varies within a few hundredths of a skin, the thickness of the spring wire does not have much effect on the capacitance characteristics. Therefore, the thickness of the spring wire should be determined by the required strength of the spring. In general, the thickness of the spring line should be between 0.3 and 1.5 mm. According to the intermediate results of the simulation, the self-capacitance of the spring sensor is generally larger than that of the solid-state conductance sensor with the same diameter. When the CSD method is used, it can be compensated by protecting the electrode.

Three, the installation requirements of the finger spring

The installation of the touch spring in PCB requires that, due to the high sensitivity of the side of the spring, the distance between the adjacent spring sensors should be as far as possible to avoid wrong detection. If the sensor spacing is small, a comparison layer can be added. The requirements for the spring sensing area are the same as those for the solid state button. If the cover is thick, the spring diameter must be at least 2 to 3 times larger than the thickness of the cover, and the distance between the PCB and the cover must be 5 mm or more. Do not place solid ground under the spring, as this complicates spring welding and increases the sensor's native capacitance.

Four, the additional functions of the touch spring

There are many additional features that can be developed with the spring, including the use of backlight sensors usually require a backlight. Using a spring as a sensor, leds can be built in for uniform front panel lighting. Can implement two types of backlight: the first is the LED installed in the upper portion of the plate can provide diffusion of backlit effect, the second is installed at the bottom of the plate LED to shoot the light through the opening up, realize the focusing effect, a wide range of scattered light is suitable for the icon of the backlight design on the front panel, and a narrow state of condenser is applicable to the design of the lamp. Two-color leds are ideal for many applications that require both backlighting and button status indication. Touching the button triggers only the sensor, while pressing the button triggers both the sensor and the mechanical button. In this case, only when the sensor is working can it provide a backlight, prompt and other preparatory actions. The final action is performed when both buttons are fired at the same time. For example, in the GPS navigation system, the touch button only displays the prompt information and can only be operated by pressing the button.