WO2017167645A1 - Method for detecting a contact of a capacitative sensor element - Google Patents

Method for detecting a contact of a capacitative sensor element Download PDF

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Publication number
WO2017167645A1
WO2017167645A1 PCT/EP2017/056993 EP2017056993W WO2017167645A1 WO 2017167645 A1 WO2017167645 A1 WO 2017167645A1 EP 2017056993 W EP2017056993 W EP 2017056993W WO 2017167645 A1 WO2017167645 A1 WO 2017167645A1
Authority
WO
WIPO (PCT)
Prior art keywords
sensor element
high
detecting
pass filter
output signal
Prior art date
Application number
PCT/EP2017/056993
Other languages
German (de)
French (fr)
Inventor
Marco Dahlhaus
Jan Freiwald
Original Assignee
Leopold Kostal Gmbh & Co. Kg
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE102016003779.2A priority Critical patent/DE102016003779A1/en
Priority to DE102016003779 priority
Application filed by Leopold Kostal Gmbh & Co. Kg filed Critical Leopold Kostal Gmbh & Co. Kg
Publication of WO2017167645A1 publication Critical patent/WO2017167645A1/en

Links

Classifications

    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03KPULSE TECHNIQUE
    • H03K17/00Electronic switching or gating, i.e. not by contact-making or -braking
    • H03K17/94Electronic switching or gating, i.e. not by contact-making or -braking characterised by the way in which the control signal is generated
    • H03K17/96Touch switches
    • H03K17/962Capacitive touch switches
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03KPULSE TECHNIQUE
    • H03K2217/00Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
    • H03K2217/94Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00 characterised by the way in which the control signal is generated
    • H03K2217/96Touch switches
    • H03K2217/9607Capacitive touch switches
    • H03K2217/96071Capacitive touch switches characterised by the detection principle
    • H03K2217/960725Charge-transfer

Abstract

The invention relates to a method for detecting a contact of a capacitive sensor element, wherein a capacitance value of the sensor element is measured by means of a continuously applied integration method, in which a voltage that is applied in each case to an integration capacitor with a known capacitance value is measured by means of an A/D converter and is processed to a raw sensor value, said raw sensor values being evaluated for detecting a contact of the sensor element. The method according to the invention is characterized in that the continuously detected raw sensor values are fed to a high-pass filter, and in that the output signal of the high-pass filter is evaluated for detecting disturbances caused by high-frequency electromagnetic radiation.

Description

 Method for detecting a touch of a capacitive

 sensor element

The invention relates to a method for detecting a contact of a capacitive sensor element, wherein a capacitance value of the sensor element is measured by means of a continuously applied integration method, wherein in each case a voltage applied to an integration capacitor having a known capacitance value measured by means of an A / D converter and to a Raw sensor value is processed, which

Raw sensor values are evaluated for detecting a touch of the sensor element.

Methods of the type discussed herein are used to evaluate capacitive proximity sensors. Such a sensor may detect the presence and, when appropriately configured, the location of a touch or approach by an object, such as a user's finger or a stylus, within a sensitive area. The touch-sensitive area can, for example, overlay a display screen. In a

In the display application, the proximity sensor may allow the user to interact directly with what is displayed on the screen rather than indirectly via a mouse or similar input device. There are a number of different types of touch sensors, such as resistive touch sensors, surface acoustic wave touch sensors, and capacitive touch sensors, the latter of which, in particular, may be detected as a mere approximation, have become the most popular. When an object touches or comes in contact with the surface of a capacitive touch sensor, a change in the capacitance value of the sensor element occurs. The task of an associated sensor control unit or of the measuring method used by it is this

Capacitance change process to capture the triggering touch or approach. The particular difficulty here is that the capacitance values of the sensor elements and in particular the changes to be detected are very small. For this reason, they are often used for their measurement so-called integration method in which small amounts of charge from the sensor element whose capacitance value is relatively small and variable, are transferred to an integration capacitor with a known fixed and significantly larger capacitance value in several successive cycles. By the German patent application DE 10 2010 041 464 A1 is a

A method for detecting a contact of a capacitive sensor element according to the preamble of claim 1 has become known.

The fact that the capacitance values of the sensor elements and

In particular, the changes to be recorded are very small, also has the consequence that the measurement is very prone to failure. Thus, erroneous detection of a supposed touch of the sensor element is possible in particular by the irradiation of high-frequency electromagnetic interference signals, although such has not occurred.

The method according to the present invention has the advantage over the previously described, with the same high sensitivity with respect to the detection of actual touches of the sensor element triggered in particular by high-frequency electromagnetic interference signals

Virtually eliminate misrecognition. This succeeds according to the invention in that the continuously recorded

Raw sensor values are fed to a high-pass filter, and that the output signal of the high-pass filter is evaluated to detect interference by high-frequency electromagnetic radiation.

The suppression of false detections is preferably carried out in that the output signal of the high-pass filter with a fixed

Limit is compared, and when exceeded the limit value by the output signal supposedly detected touches are marked as invalid.

In an advantageous embodiment of the inventive method is provided that in the integration process in several successive integration cycles small amounts of charge from the sensor element to the integration capacitor whose capacitance value is large compared to that of the sensor element, and subsequently applied to the integration capacitor voltage by means of a A / D converter is measured. In the following, the invention is with reference to the attached

Drawing explained.

 The single figure shows the application of a high-pass filter for detecting high-frequency electromagnetic radiation in the evaluation of the raw sensor values of a touch-sensitive sensor element as a flowchart.

In step 1, raw sensor values of a touch-sensitive

Sensor element detected by a capacitive measuring method. These raw sensor values are then supplied to both a touch detection 2 and a high-pass filter 3. The high-pass filter 3 is used for Detection of interference from high-frequency electromagnetic

Radiation.

Only if no fault is detected and a touch is identified at the same time, the touch may be output as valid. Error detections are thus suppressed.

Touch recognition 2 has three different possible output values. If the currently detected raw sensor value is between a lower limit and an upper limit, the output signal "None

 Contact "KB is output If the currently detected raw sensor value is above the upper limit value, the output signal" Detected touch "BE is output. If the currently detected raw sensor value is below the lower limit, this indicates a hardware failure that requires the initiation of a safe state, ie the deactivation of the touch detection. In this case, therefore, the output signal "Fault Detected" SE is output.

The high pass filter 3 has two different possible output values. When the output signal of the high-pass filter 3 is below an upper limit value, the output signal "No disturbance" KS is outputted When the output signal of the high-pass filter 3 is above this upper limit value, the output signal "Fault Detected" SE is output. A touch is only recognized as valid and output in method step BA if the output signal of the touch detection 2 is "touch detected" BE, and at the same time the high-pass filter 3 outputs "no fault" KS. When the touch detection 2 outputs the output signal "Fault Detected" SE, and at the same time the high-pass filter 3 outputs "No Interference" KS the system stopped. There is probably a hardware error in which further operation of the touch detection is not possible.

When the touch detection 2 outputs the output signal "no touch" KB, or the high-pass filter 3 outputs "failure detected" SE, a re-measurement is started, not unlike after a contact recognized as valid and issued in step BA.

Claims

claims
1 . Method for detecting a touch of a capacitive
 Sensor element, wherein a capacitance value of the sensor element is measured by means of a continuously applied integration method, wherein each of a voltage applied to an integration capacitor with a known capacitance value voltage is measured by means of an A / D converter and processed to a Sensorrohwert, which
 Raw sensor values are evaluated for detecting a touch of the sensor element, characterized in that the continuously detected raw sensor values are fed to a high-pass filter, and that the output signal of the high-pass filter for detecting
 Interference from high-frequency electromagnetic radiation is evaluated.
2. The method according to claim 1, characterized in that the
 Output of the high-pass filter is compared with a predetermined limit and when the limit is exceeded by the
 Output signal supposedly detected touches as invalid
 be marked.
3. The method according to claim 1 or 2, characterized in that in the integration process in several successive
Integration cycles small amounts of charge from the sensor element to the integration capacitor whose capacitance value is large compared to that of the sensor element, are transmitted, and subsequently the voltage applied to the integration capacitor voltage is measured by means of an A / D converter.
4. The method according to any one of claims 1 to 3, characterized in that the raw sensor values are also evaluated for detecting hardware errors of the sensor element.
5. The method according to claim 4, characterized in that the
 Output signal of the high-pass filter is compared with a predetermined limit and when exceeded the limit value by the output signal supposedly detected hardware errors are marked as invalid.
PCT/EP2017/056993 2016-03-26 2017-03-23 Method for detecting a contact of a capacitative sensor element WO2017167645A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE102016003779.2A DE102016003779A1 (en) 2016-03-26 2016-03-26 Method for detecting a contact of a capacitive sensor element
DE102016003779 2016-03-26

Publications (1)

Publication Number Publication Date
WO2017167645A1 true WO2017167645A1 (en) 2017-10-05

Family

ID=58410334

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2017/056993 WO2017167645A1 (en) 2016-03-26 2017-03-23 Method for detecting a contact of a capacitative sensor element

Country Status (2)

Country Link
DE (1) DE102016003779A1 (en)
WO (1) WO2017167645A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7031886B1 (en) * 2004-12-14 2006-04-18 Synaptics Incorporated Methods and systems for detecting noise in a position sensor using minor shifts in sensing frequency
WO2009070814A2 (en) * 2007-11-27 2009-06-04 Frederick Johannes Bruwer Capacitive sensing circuit with noise rejection
DE102010041464A1 (en) 2009-09-25 2011-04-14 Atmel Corporation, San Jose Method and apparatus for measuring the self-capacitance using a single pins

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7031886B1 (en) * 2004-12-14 2006-04-18 Synaptics Incorporated Methods and systems for detecting noise in a position sensor using minor shifts in sensing frequency
WO2009070814A2 (en) * 2007-11-27 2009-06-04 Frederick Johannes Bruwer Capacitive sensing circuit with noise rejection
DE102010041464A1 (en) 2009-09-25 2011-04-14 Atmel Corporation, San Jose Method and apparatus for measuring the self-capacitance using a single pins

Also Published As

Publication number Publication date
DE102016003779A1 (en) 2017-09-28

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