Single-Wire Safety Relay Architecture for Global E-Stop Sharing
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Solution Overview
Problem
Modern industrial automation systems face challenges in ensuring reliable safety responses without dual redundant signal channels, which increase wiring complexity and risk of cross faults, while also needing to share global emergency stop signals between independent safety systems.
Innovation Solution
A single-wire safety system architecture that uses a safety master device with a pulse verification component, relay control, and networking capabilities to monitor pulse signals, disconnect power when unsafe conditions are detected, and send diagnostic messages, allowing for global emergency stop signals to be shared between safety systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual redundant signal channels are used to ensure reliable safety responses, then safety reliability is improved, but wiring complexity and risk of cross faults increase
Solution Approach 1:
The patent combines multiple safety functions (signal transmission, fault detection, and device identification) into a single-wire safety channel. The safety master device communicates with multiple safety input devices through one shared communication channel, eliminating the need for dual redundant wiring while maintaining safety reliability through intelligent protocol design and fault detection capabilities.
Solution Approach 2:
The single-wire safety channel serves multiple functions: transmitting safety signals, detecting faults, identifying devices, and enabling global emergency stop propagation. This multi-functional approach replaces traditional dedicated redundant wiring with a versatile communication channel that handles various safety tasks through software and protocol intelligence.
2Reliability
If independent safety systems are used for different safety circuits, then system independence is maintained, but global emergency stop signal sharing is prevented
Solution Approach 1:
The safety master device acts as an intermediary that receives global emergency stop signals from one safety circuit and propagates them to other networked safety master devices. This mediator approach allows independent safety circuits to share emergency stop functionality through the network communication channel without compromising their operational independence or requiring direct physical connections between circuits.
3Device complexity
If a single-wire safety channel is used to reduce wiring complexity, then device complexity is reduced, but diagnostic capability and device identification become more difficult
Solution Approach 1:
The safety master device implements feedback mechanisms by sending diagnostic messages through the single-wire safety channel and receiving response messages from safety input devices. This feedback loop enables the master device to identify which specific device caused a safety signal loss, providing comprehensive diagnostic capability despite the simplified single-wire architecture.
Data Source
AI summary
A single-wire safety system architecture yields reliable safety device monitoring without the need for dual redundant signal channels. The safety system comprises a safety relay and one or more compatible safety input devices connected in series with the safety relay via a single-wire communication circuit. A safety signal with a recognizable pulse pattern traverses the single-wire safety circuit to the safety relay via the safety devices. The safety relay opens its contactors and deenergizes its associated industrial equipment if the pulse pattern is not received and recognized. The safety relay can also be configured to initiate a global emergency stop in response to a loss of a safety function by one of its safety input devices, the global emergency stop instructing other safety relays of other safety circuits to open their contactors and enter safe mode.