Single-Wire Safety Relay Communication Without Redundant Channels
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Industrial safety systems require reliable monitoring of safety input devices without the need for dual redundant signal channels, which are cumbersome and prone to cross faults, while maintaining high safety reliability.
Innovation Solution
A single-wire safety system architecture that uses a comms master and safety devices configured for single-wire safety communication, where a safety master generates a pulse train that is passed through each device, and upon detecting a safe state, isolates power to industrial components, utilizing bi-directional communication for status and diagnostic information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual redundant signal channels are used for safety monitoring, then safety reliability is improved, but device complexity and susceptibility to cross faults increase
Solution Approach 1:
The patent merges safety monitoring and diagnostic communication functions into a single-wire interface. The safety device communicates both safety status and diagnostic information through one shared communication channel, eliminating the need for separate redundant signal channels while maintaining safety reliability through integrated monitoring capabilities.
Solution Approach 2:
The single-wire interface serves multiple functions simultaneously: it transmits safety signals, carries diagnostic data, enables bidirectional communication, and provides device status monitoring. This multi-functional approach replaces traditional multi-channel redundant safety systems, reducing complexity while preserving safety integrity.
2Reliability
If dual redundant signal channels are used for safety monitoring, then safety reliability is improved, but potential faults increase
Solution Approach 1:
By consolidating safety monitoring and diagnostic functions into a single-wire interface, the patent eliminates the cross faults that can occur between multiple redundant channels. The unified communication path removes the possibility of inter-channel interference while maintaining comprehensive safety monitoring through integrated diagnostics.
3Device complexity
If single-wire communication is used for safety devices, then device complexity is reduced, but communication capability for diagnostics is limited
Solution Approach 1:
The single-wire interface is designed to handle multiple communication tasks simultaneously: safety status transmission, diagnostic data exchange, bidirectional communication, and device configuration. This multi-functional capability ensures that diagnostic information is not lost despite the reduced physical channel complexity.
Solution Approach 2:
The system employs periodic communication cycles where safety signals and diagnostic data are transmitted in structured time-multiplexed sequences. This periodic action allows comprehensive diagnostic information to be conveyed through the single-wire interface without compromising safety signal integrity.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A single-wire safety system architecture is provided that yields reliable safety device monitoring without the need for dual redundant signal channels. The safety system comprises a safety relay acting as a communications master device and one or more compatible safety devices connected in series with the safety relay via a single-wire communication circuit. The safety device farthest from the safety relay on the safety circuit modulates a safety signal with a recognizable pulse pattern that traverses the single-wire safety circuit to the safety relay via the intermediate safety devices. The safety relay maintains safety mode as long as the pulse pattern is received and recognized. The architecture allows bi-directional communication of initialization, configuration, and diagnostic messages over the single-wire safety channel, and can also allow safety devices to insert prognostic data into the safety signal in order to convey health information while the system is in normal operation mode.