Projektarbeit: Touch Sensing with

Time Domain Reflectometry

Markus ZimmermannBetreuer: Raphael Wimmer

Outline

• Introduction• Hardware• Signal Analysis• Applications• Demonstration• Discussion

Introduction: Time Domain Reflectometry

Reflections

• Termination• Capacitive / Resistive / Inductive

Present usage

• Wiring maintainance (communication, aaviation)

• Agricultural and geotechnical (humidity, ...)• Semiconductor/circuit board analysis• New Approach: Touch Sensing

Hardware: Tektronix 1502

• Characteristics

Signal Analysis

• Acquisition• Filter• Motion Smoothing• Calibration• Detection• Mapping

Stage 1: Acquisition

• Camera• OpenCV

Stage 2: Filter

• Averaging in Frequency Domain

Convolution / FFT

• Explanation of Convolution Filtering

Stage 3: Motion Smoothing

• Stability depends on Alteration, Gradient

Stage 4: Calibration

• Thresholds, Gradients

Stage 5: Detection

Stage 4: Mapping

Applications

„Wire“

„Snake“

„Fractal“

Applications: Outlook

• Wiring 3D Objects• ITO evaporation

Demonstration

• Video

Discussion

• Prototyping Technique• Noisy• HF interferences• Increasing Resolution

Conclusion

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