Rotary Encoder Debouncing Circuit for Adaptive Edge Filtering

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Solution Overview

Problem

Existing debouncing circuits for rotary encoders are costly, inefficient, and often ineffective, especially in hand-driven applications where unpredictable pulse trains occur, limiting the speed range of decoding.

Innovation Solution

A debouncing circuit that includes an edge detector circuit, a pulse skip and reset circuit, and a sampling circuit, which self-adaptively debounces signals without a timer, ensuring clean input signals for accurate decoding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional debouncing circuits are used, then bouncing effects are removed, but the circuit cost increases and decoding speed range is limited

Engineering Contradiction:

Improvesignal cleanlinessVSAvoidcircuit cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces traditional hardware debouncing circuits with a software-based debouncing algorithm implemented on the microcontroller. The algorithm uses timestamp comparison and state machine logic to detect and filter bounce effects, eliminating the need for additional debouncing ICs or complex hardware circuits while maintaining signal reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The microcontroller performs its own signal debouncing using integrated timing resources and processing capability. The system uses its internal clock and timer units to implement the debouncing logic, making the microcontroller self-sufficient and eliminating external debouncing components.

Inventive Principle:

Principle #25Self-service

2Speed

If software debouncing is implemented, then decoding speed range improves, but processing time increases

Engineering Contradiction:

Improvedecoding speed rangeVSAvoidprocessing delay

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The system records timestamps of signal transitions and uses pre-defined debounce time thresholds to determine valid edges. By preparing timestamp data and using pre-calculated debounce parameters, the system minimizes processing delay while maintaining accurate bounce detection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The debouncing algorithm uses periodic timestamp comparison and state machine transitions that operate synchronously with the encoder signal frequency. This periodic processing approach ensures consistent debounce timing without introducing variable delays, maintaining decoding speed across different rotation rates.

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS12316325B2Circuits and methods for debouncing signals produced by a rotary encoder

Publication Date: 2025.05.27 STMICROELECTRONICS SRL

AI summary

A first input node receives a first input signal and a second input node receives a second input signal. The first and second input signals are in phase quadrature. An edge detector circuit senses the first input signal and produces a pulsed signal indicative of edges detected in the first input signal. A pulse skip and reset circuit senses the pulsed signal and the second input signal, and produces a reset signal indicative of pulses detected in the pulsed signal while the second input signal is de-asserted. A sampling circuit senses the second input signal and the reset signal, and produces an output signal that is deasserted in response to assertion of the second input signal and is asserted in response to a pulse being detected in the reset signal.