Resistive Touch Actuator Signal Stabilization for Force-Invariant Dimming
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Solution Overview
Problem
Conventional touch dimmers are responsive to both the force and position of a point actuation, leading to undesired intensity control when lightly pressed, as the contact resistance varies with actuation force, making them unreliable for precise position-based control.
Innovation Solution
A load control device incorporating a semiconductor switch, a controller, a touch-sensitive actuator, and stabilizing circuits that filter out transient voltage changes due to low-pressure touches, ensuring the control signal is responsive only to the position of the actuation, using a resistive-capacitive circuit with a filter capacitor to prevent large transient voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a touch-sensitive actuator responds to both force and position of actuation, then the device can detect user input across a range of pressures, but the contact resistance varies with actuation force causing unreliable intensity control
Solution Approach 1:
The patent segments the actuation response into two independent components: a force-detection component (whacker circuit) and a position-detection component (voltage divider circuit). This segmentation allows the system to separately process force information for trigger validation and position information for intensity control, eliminating the coupling between force and position responses that causes reliability issues.
Solution Approach 2:
The patent introduces a microcontroller as an intermediary that processes signals from both the whacker circuit and voltage divider circuit. The microcontroller acts as a mediator that validates force-based triggers and then uses position-based voltage readings to control dimming, separating the control functions and preventing direct coupling between force and position effects.
2Ease of operation
If the touch dimmer uses contact resistance variation to control intensity, then the device can respond to different actuation forces, but lightly pressed touches cause undesired intensity changes
Solution Approach 1:
The patent extracts the force-detection function into a separate whacker circuit that only provides trigger validation, while the intensity control is extracted to depend solely on position information from the voltage divider circuit. This extraction eliminates the harmful coupling where light touches cause undesired intensity changes.
Solution Approach 2:
The patent changes the operational parameter for intensity control from contact resistance (which varies with force) to voltage division ratio (which varies with position). This parameter change allows the system to maintain touch responsiveness while achieving accurate intensity control based on position rather than force magnitude.
3Measurement precision
If the touch-sensitive actuator has varying contact resistance with actuation force, then the device can detect different pressure levels, but the control signal becomes unreliable for position-based dimming
Solution Approach 1:
The patent segments the measurement functions into separate circuits: the whacker circuit measures actuation force for trigger detection, while the voltage divider circuit measures position for dimming control. This segmentation prevents the contact resistance variations from contaminating the position signal.
Solution Approach 2:
The patent implements feedback through the microcontroller that monitors both the whacker circuit output and voltage divider output. The system uses feedback to validate that a sufficient force was applied (via whacker) before accepting position information (via voltage divider) for intensity control, ensuring reliable position-based dimming.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a touch dimmer that is not responsive to light touches, ensuring accurate control of lighting intensity based solely on the position of actuation, enhancing user experience by maintaining consistent control signals regardless of actuation force.
Implementation Method 1
An elastomer is received by an opening in the rear surface of the bezel. The elastomer is positioned between the bezel and the touch-sensitive device, such that a press on the front surface of the bezel is transmitted to the conductive element of the touch-sensitive device.
Data Source
AI summary
A user interface for a lighting control, the user interface comprising a touch sensitive front surface having a longitudinal axis and a lateral axis; a four-wire resistive touch pad responsive to a point actuation on the touch sensitive front surface, the resistive touch pad having a longitudinal resistive element for providing a first control signal representative of the position of the point actuation along the longitudinal axis, and a lateral resistive element for providing a second control signal representative of the position of the point actuation along the lateral axis; a controller operable to receive the first and second control signals; a first capacitor adapted to be coupled between the lateral resistive element and a circuit common, the first capacitor operable to charge and discharge through the longitudinal resistive element of the resistive touch pad to stabilize the first control signal; and first, second, and third switches responsive to the controller, each of the switches comprising first, second, and third terminals, and operable to be controlled between a first position in which the first terminal is electrically connected to the second terminal, and a second position in which the first terminal is electrically connected to the third terminal, the switches coupled to the touch sensitive device, such that when the controller controls all of the switches to the first position, a DC supply voltage is coupled across the longitudinal resistive element, the controller is coupled to the lateral resistive element, and the first capacitor is coupled between the lateral resistive element and the circuit common, and when the controller controls all of the switches to the second position, the DC supply voltage is coupled across the lateral resistive element and the controller is coupled to the longitudinal resistive element;wherein the controller is operable to determine, from the second control signal, if the touch sensitive front surface is presently being actuated, and to determine, from the first control signal, the position of the point actuation along the longitudinal axis.