Bus Communication Terminal Detection Using Pulse Width Measurement
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Solution Overview
Problem
In air-conditioning systems with bus-connected cordless extension units, identifying the communication device near the terminal end of a communication line is challenging, especially in large installations, due to signal reflection issues and the need for manual adjustment of terminating resistors when units are added or removed.
Innovation Solution
A detection device connected to the communication line that receives signals with prescribed pulse widths, measures pulse widths, and identifies the communication device near the terminal end by detecting the shortest pulse width, allowing for automatic setting of terminating resistors to minimize signal reflection and maintain stable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of cordless extension units is increased or communication wiring length is increased to expand system coverage, then system versatility and area coverage are improved, but signal reflection increases and communication stability deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of terminating resistor settings based on real-time detection of communication line characteristics. The base device automatically detects the number of connected extension units and adjusts the terminating resistor value accordingly, transforming a static configuration into a dynamic adaptive system that maintains communication stability regardless of system expansion
Solution Approach 2:
The patent changes the parameter of terminating resistor value based on the detected number of extension units. By varying the resistor parameter dynamically (e.g., selecting from different resistance values), the system optimizes signal termination for different communication line lengths and configurations, preventing signal reflection and maintaining communication reliability
2Reliability
If manual adjustment of terminating resistors is performed to optimize communication, then communication stability is improved, but operation complexity and time consumption increase
Solution Approach 1:
The patent enables the base device to automatically detect the number of connected extension units and self-adjust the terminating resistor setting without manual intervention. The system performs self-diagnosis and self-configuration, eliminating the need for operators to manually find and adjust terminating resistors on extension units
Solution Approach 2:
The patent implements a feedback mechanism where the base device detects communication line characteristics (number of extension units) and uses this feedback information to automatically adjust the terminating resistor setting. This closed-loop control ensures optimal communication stability without requiring manual operation
3Reliability
If terminating resistors are set in extension units to minimize signal reflection, then communication quality is improved, but device complexity and configuration difficulty increase
Solution Approach 1:
The patent makes the base device universal by equipping it with both communication management functions and terminating resistor adjustment capabilities. The base device can serve as the sole terminating point for the communication line, eliminating the need for terminating resistors in extension units and simplifying the overall system configuration
Solution Approach 2:
The patent extracts the terminating resistor function from the extension units and consolidates it in the base device. By removing the need for terminating resistors from distributed extension units, the system reduces configuration complexity while maintaining signal quality through centralized termination control
Data Source
AI summary
A detection device is connected to a plurality of communication devices by a communication line. The detection device has a reception unit, a measurement unit, and a detection unit. The reception unit receives signals with prescribed pulse widths transmitted from the plurality of communication devices, respectively. The measurement unit measures the pulse widths of the signals received by the reception unit. The detection unit is configured to detect the communication device disposed near a terminal end of the communication line as a terminal-end communication device on the basis of the plurality of pulse widths measured by the measurement unit.