Non-contact keyboard capacitance sensor and input method

Abstract

The invention discloses a non-contact keyboard capacitance sensor and a key position input method. The non-contact keyboard capacitance sensor comprises a power supply circuit, a capacitance sensor, acapacitance-to-digital conversion circuit, a control module, a state feedback control circuit, an indicator and a communication circuit. The capacitance sensor comprises a first electrode arranged onthe outer side of the periphery of the key position, a second electrode arranged on the periphery of the key position and a third electrode arranged in the center of the key position, wherein any electrode is at least a double-bond position, and the third electrode sinks by 0.8-3.5 mm compared with the second electrode; the three-dimensional position of the finger on the keyboard is determined bydetecting the self-capacitance of each electrode, and a three-state response of the finger pointing to the key position is provided and inputted through the feedback control circuit. The invention provides a low-cost and mature CDC chip technology which is reasonable in structural design and high in resolution, effectively resists various interferences and makes full use of capacitance detection,and a commercial non-contact input solution which can be popularized and promoted is provided for sanitation sensitivity.

Description

Technical field [0001] This application relates to a non-contact keyboard capacitive sensor and input method, which is suitable for public health keyboard buttons, especially sanitary sensitive sensor buttons, such as access control keyboards, POS keyboards and ATM keyboards. Background technique [0002] The emergence of the new crown pneumonia epidemic, coupled with the seasonal flu and other situations, the disinfection of elevators, especially the disinfection of button switches, is facing a huge workload, and it is even difficult to disinfect the virus. For this reason, there is a sense of proximity in society. The need for buttons is due to the direct contact with button switches in public areas, such as elevator floor selection and door opening and closing buttons, toilet flush switches, public drinking water switches, etc., which can easily lead to infectious diseases. Non-contact buttons can avoid this. risks of. [0003] For the proximity of the human body, especially th...

AI Technical Summary

Problems solved by technology

[0004] Chinese patent 201480079328 discloses a technical solution for using gestures to control elevators. In its specification, technologies such as photography are mentioned to record gestures, including preset gestures. The data records in the system form a gesture library, and then after a gesture command is detected, it is compared with the gesture library to determine the meaning of the gesture, which is a bit similar to the face recognition technology that has become popular at present; the technology requires There are many and expensive hardware devices. On the other hand, user customization is also very difficult. Due to the strangeness of human gestures and movements, this technology has considerable challenges in accurately judging the two contradictions of recognition and anti-interference. , there is no such product on the market, which indirectly shows the difficulty of the technology

[0012] However, for access control and vending machines, especially POS and ATM machines with about a dozen keypads, since the size of each key is very small, even its layout has been solidified. It is quite difficult to make a separate electrode that can judge the approach of a finger instead of touching the key. Therefore, despite the cost advantage of the capacitive sensor, although the capacitance-to-digital conversion circuit used in the capacitive sensor is quite mature, it is difficult to obtain a solid-sized keypad type. In terms of products, there is currently no non-contact commercial application on the market, and its hygiene-sensitive requirements are becoming stronger and stronger

[0013] Chinese patent 201710893997 establishes four sensing electrodes around the display screen to detect the stereotaxic positioning of the fingers without contact. Although electronic means such as installing shielding electrodes and equipotentials are adopted, in fact, the influence of the fingers and the palm behind the fingers on the electrodes, And the impact of different angles of human finger pointing action makes this technical solution unable to accurately locate the finger and cannot realize commercial application

[0014] Chinese patent 201110130539 discloses a non-contact technical solution for a small keyboard with a USB interface. This technical solution does not disclose how the capacitive electrodes are constructed. It only discloses the use of a capacitive sensor using Freescale's inductive sensor chip MC34940. The chip has 7 The channel for measuring capacitance obviously cannot meet the needs of at least ten numeric keypads such as the need to enter passwords

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