Capacitive Presence Sensor With Dynamic ADC Reference Control
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Solution Overview
Problem
Existing capacitive proximity sensors for motor vehicles face issues with low sensitivity and high electromagnetic interference, leading to short detection distances and time-consuming user presence detection, particularly in CVD and DCVD systems.
Innovation Solution
A sensor system with a microcontroller and capacitive voltage divider that dynamically sets the reference voltage using a resistive module and capacitive module, optimizing sensitivity and reducing current consumption, while incorporating an initialization phase, reference acquisition phase, and measurement phase to detect user presence effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CVD or DCVD sensor systems are used for presence detection, then rapid detection and measurement capability is achieved, but electromagnetic interference and low-frequency noise increase significantly
Solution Approach 1:
The patent applies dynamics by making the reference voltage adjustable and adaptable rather than fixed. The microcontroller dynamically adjusts the reference voltage based on detected noise levels and operating conditions, allowing the system to optimize performance while minimizing electromagnetic interference. This is achieved through configurable reference voltage values that can be selected from multiple predefined levels or dynamically adjusted during operation.
Solution Approach 2:
The patent changes the reference voltage parameter to resolve the contradiction. By providing multiple predefined reference voltage values (e.g., 1.024V, 2.048V, 4.096V, 8.192V) and allowing dynamic selection among them, the system can adapt to different operating conditions. This parameter change enables the system to reduce electromagnetic interference by selecting appropriate reference voltage levels while maintaining detection accuracy.
2Device complexity
If standard reference voltage configuration is used in analog-digital converter, then device complexity is reduced, but sensitivity and detection distance are limited
Solution Approach 1:
The microcontroller's input-output port serves multiple functions: it acts as a digital input for presence detection, a digital output for controlling the capacitive sensor charging, and a configurable reference voltage input for the analog-digital converter. This multi-functionality eliminates the need for separate dedicated reference voltage generation circuitry, reducing component count while maintaining high sensitivity through adjustable reference voltage.
Solution Approach 2:
The microcontroller internally generates and provides the reference voltage to its own analog-digital converter without requiring external reference voltage circuitry. The microcontroller's input-output port is configured to output the reference voltage directly to the ADC, allowing the system to be self-sufficient and eliminate additional components while maintaining measurement precision.
3Stability of the object's composition
If fixed reference voltage is used in capacitive sensor system, then system stability is improved, but adaptability to different detection conditions is reduced
Solution Approach 1:
The system transitions from a fixed reference voltage to a dynamic, adjustable reference voltage. The microcontroller can select from multiple predefined reference voltage values or dynamically adjust the reference voltage based on detected conditions such as noise levels, detection distance requirements, or environmental factors. This dynamic approach maintains system stability through controlled adjustment while providing adaptability to different detection scenarios.
Solution Approach 2:
The system performs preliminary action by pre-configuring multiple reference voltage values (e.g., 1.024V, 2.048V, 4.096V, 8.192V) that can be selected based on anticipated operating conditions. This allows the system to be pre-adapted to different detection scenarios without requiring real-time complex calculations, maintaining stability while providing adaptability.
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 enhances sensitivity and reduces electromagnetic interference, allowing for improved detection distance and speed of user presence, while minimizing component count and current consumption.
Implementation Method 1
the user acts as a second electrode, connected to ground, which increases the capacitance value of the detection capacitor beyond its nominal capacitance value measured in the absence of a user
Implementation Method 2
the detection capacitor being charged by the voltage generator, followed, secondly, by the conductive transfer of current from the charge stored in the detection capacitor to the storage capacitor
Data Source
AI summary
A presence detection sensor for unlocking an opening panel of a motor vehicle, said sensor comprising a microcontroller implementing an analog-digital converter and comprising a first input, a second input forming the voltage reference of said analog-digital converter, a third input for supplying the microcontroller with voltage, and a plurality of inputs-outputs, and a capacitive voltage divider connected to at least one of the inputs-outputs of the plurality of inputs-outputs. The sensor comprises a resistive module connected between the first input and the second input of the microcontroller and a capacitive module connected between the second input of the microcontroller and a ground.