Capacitative sensor system
First Claim
1. A circuit arrangement for generating an output signal correlated with an approach based on changes of the dielectric properties of the environment of a sensor electrode, the circuit arrangement comprising:
- a sensor electrode that at least partly juxtaposed with an observation area;
a microcontroller outputting a square-wave voltage;
a voltage attenuation circuit external to said microcontroller receiving the square-wave voltage, the voltage attenuation circuit being directly connected between an output of the microcontroller and ground and adjusting a level of the square-wave voltage outputted by the microcontroller, wherein the voltage attenuation comprises an output connected with the sensor electrode via a charging resistor; and
a field-effect transistor (FET) operating as an impedance converter comprising a gate terminal directly connected with the sensor electrode and via the charging resistor with the output of the voltage attenuation circuit, wherein the charging resistor is dimensioned such that during a semi-period of the square-wave voltage an almost complete charge and discharge at the gate terminal of the FET occurs.
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Accused Products
Abstract
The invention relates to a capacitive sensor system, in particular for detecting the approach of objects and in particular also for gesture recognition. The problem of the present invention is to provide a capacitively operating sensor system, which can be implemented with low component complexity and thus low costs and space requirements and is also characterized by low power consumption, so as to operate with batteries having a low charge capacity and/or a long operating time. Said problem is solved according to the invention by a circuit configuration for generating an output signal correlating with an approximation process based on changes in the dielectric properties of the surroundings of a sensor electrode, having a sensor electrode which is adjacent to an observation area in at least some sections, a microcontroller circuit (μC) for output of an alternating voltage, a voltage divider circuit for achieving an adjustment of the level of the alternating voltage output by the microcontroller (μC), and a field effect transistor (FET) in the function of an impedance converter, wherein the field effect transistor is incorporated into the circuit configuration in such a way that the voltage output by the voltage divider circuit is present at the gate input thereof and at the same time at the sensor electrode (ES).
38 Citations
21 Claims
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1. A circuit arrangement for generating an output signal correlated with an approach based on changes of the dielectric properties of the environment of a sensor electrode, the circuit arrangement comprising:
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a sensor electrode that at least partly juxtaposed with an observation area; a microcontroller outputting a square-wave voltage; a voltage attenuation circuit external to said microcontroller receiving the square-wave voltage, the voltage attenuation circuit being directly connected between an output of the microcontroller and ground and adjusting a level of the square-wave voltage outputted by the microcontroller, wherein the voltage attenuation comprises an output connected with the sensor electrode via a charging resistor; and a field-effect transistor (FET) operating as an impedance converter comprising a gate terminal directly connected with the sensor electrode and via the charging resistor with the output of the voltage attenuation circuit, wherein the charging resistor is dimensioned such that during a semi-period of the square-wave voltage an almost complete charge and discharge at the gate terminal of the FET occurs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A circuit arrangement for generating an output signal correlating with an approach of the dielectric properties of the environment because of changes of a sensor electrode, the circuit arrangement comprising:
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a sensor electrode at least partly juxtaposed with an observation area; a microcontroller outputting a square-wave voltage; a voltage divider external to said microcontroller and being directly connected between an output of the microcontroller and ground and operable to adjust a level of the square-wave voltage outputted by the microcontroller; and a field-effect transistor operating as an impedance converter and configured in such a way that an approach is detected based on an event correlating with the change of a ratio of charging time to discharging time, wherein an output of the voltage divider is connected via a charging resistor to a gate of the field effect transistor and to the sensor electrode, wherein the gate of the field effect transistor is directly connected with the sensor electrode and a drain of the field effect transistor is connected with a supply voltage, and wherein the charging resistor is dimensioned such that during a semi-period of the square-wave voltage an almost complete charge and discharge at the gate terminal of the FET occurs.
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19. A circuit arrangement for generating an output signal correlated with an approach based on changes of the dielectric properties of the environment of a sensor electrode, the circuit arrangement comprising:
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a sensor electrode that at least partly juxtaposed with an observation area; a microcontroller outputting a square-wave voltage; a voltage divider comprising a first and second resistor directly connected in series between an output of the microcontroller and ground for adjusting a level of the square-wave voltage outputted by the microcontroller; and wherein the circuit arrangement further comprises a field effect transistor (FET) stage with only a single FET, wherein the FET having a gate terminal connected directly with the sensor electrode and operating as an impedance converter and integrated into the circuit arrangement in such a way that the voltage outputted by the voltage divider is connected via a charging resistor with the gate terminal and the sensor electrode, wherein the charging resistor is dimensioned such that during a semi-period of the square-wave voltage an almost complete charge and discharge at the gate terminal of the FET occurs. - View Dependent Claims (20)
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21. A circuit arrangement for generating an output signal correlated with an approach based on changes of the dielectric properties of the environment of a sensor electrode, the circuit arrangement comprising:
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a sensor electrode that at least partly juxtaposed with an observation area; a microcontroller outputting a square-wave voltage; a voltage divider for adjusting a level of the square-wave voltage outputted by the microcontroller being directly connected between an output of the microcontroller and ground, wherein the voltage attenuation comprises an output connected with the sensor electrode via a charging resistor; and wherein the circuit arrangement further comprises a field effect transistor stage with only a single FET, wherein the single FET operates as an impedance converter comprising a gate terminal directly connected with the sensor electrode and via the charging resistor with the output of the voltage attenuation circuit and wherein a source of the FET provides the output signal.
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Specification