Capacitive Touch Electrode Sampling Across Scan Rate Changes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive touch sensor devices face inaccuracies due to manufacturing variations and changes in electrode scan rates, leading to complex compensation calculations and increased power consumption for calibration, especially when detecting touch and release events in varying environments.
Innovation Solution
The system selectively uses settled voltage samples from capacitive touch sense electrodes by discarding initial samples when the scan rate changes, ensuring accurate detection of touch and release events without requiring frequent recalibrations, thus reducing computational complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If electrode scan rate is increased to achieve faster reaction time, then response speed is improved, but measurement precision deteriorates due to capacitive coupling errors and voltage settling issues
Solution Approach 1:
The patent applies preliminary action by performing a settling period before ADC conversion when scan rate changes occur. The system waits for the capacitive coupling voltage to stabilize before taking measurements, preventing measurement errors caused by transient voltage fluctuations. This preliminary waiting period ensures accurate readings while maintaining the ability to use higher scan rates for faster response.
2Measurement precision
If complex compensation calculations are performed to correct electrode value variations, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts and eliminates the need for complex compensation calculations by using settled voltage samples exclusively. Instead of performing sophisticated software-based offset compensation, the system simply discards initial unsettled samples and uses only stable samples for measurement. This extraction of the problematic compensation step significantly reduces computational complexity while maintaining measurement accuracy.
3Measurement precision
If periodic recalibrations are performed to adjust compensation offsets for environmental changes, then measurement precision is improved, but power consumption and device complexity increase
Solution Approach 1:
The patent applies self-service by allowing the system to automatically use settled voltage samples that inherently compensate for environmental variations. The settled samples naturally account for temperature and other environmental effects without requiring external recalibration interventions. This self-adjusting mechanism eliminates periodic recalibration operations, reducing power consumption while maintaining precision across varying environmental conditions.
Data Source
AI summary
A touch sensitive capacitive keypad system (100) is provided with an analog-to-digital converter, a keypad sensing electrode (114) coupledto measure capacitance voltages using a configurable electrode scan rate, and a controller (120) configured to provide scan-rate independent capacitance voltage measurements from the keypad sensing electrode to the analog-to-digital converter when there is a change in the configurable electrode scan rate by repetitively sampling a capacitance voltage measurements (e.g., 524a-f) from the keypad sensing electrode over a plurality of sequential electrode scan cycles and then discarding a predetermined number of the capacitance voltage measurements (e.g., 524a-b) to generate the scan-rate independent capacitance voltage measurements (e.g., 524c-f) that are provided to the analog-to-digital converter.