Latching Relay Reset Circuit for Safe Power-Loss Recovery
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Solution Overview
Problem
Latching relays in industrial process field devices fail to reset after power interruptions, leading to potentially dangerous or damaging conditions due to external devices remaining activated.
Innovation Solution
A reset circuit is integrated into the field device, utilizing a comparator and charge reservoir to detect power interruptions and reset the latching relay, ensuring the device returns to a safe state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a latching relay is used to conserve power in the field device, then power consumption is reduced, but the relay cannot reset after power loss which creates safety hazards
Solution Approach 1:
The power management function is segmented into two independent circuits: a low-power latching relay circuit for normal operation and a separate reset circuit with its own power source (supercapacitor) for safety functions. This segmentation allows the main device to operate with minimal power while maintaining the ability to reset the relay after power loss, thus resolving the contradiction between power conservation and safety reliability.
Solution Approach 2:
A supercapacitor is introduced as an intermediary energy storage device between the power loss event and the relay reset function. The supercapacitor captures residual energy during normal operation and releases it during power loss to activate the reset circuit, enabling the relay to reset without requiring continuous power from the main supply, thus maintaining both low power consumption and safety reliability.
2Reliability
If a reset circuit is added to enable relay reset after power loss, then safety is improved, but device complexity increases
Solution Approach 1:
The reset circuit recovers and utilizes the residual energy stored in the supercapacitor after power loss instead of discarding it. By detecting the power loss condition and automatically discharging the supercapacitor through the relay coil to reset the relay, the circuit achieves safety functionality without requiring additional complex power management components or external power sources.
Solution Approach 2:
The reset circuit is designed to be self-activating upon power loss detection, eliminating the need for external control signals or complex control logic. The circuit automatically detects power loss conditions, activates the supercapacitor discharge path, and resets the relay without human intervention or additional control system involvement, thus improving safety while minimizing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The reset circuit effectively deactivates external devices during power losses, preventing damage and ensuring safety by resetting the latching relay, thus addressing the issue of latching relays maintaining their state post-interruption.
Implementation Method 1
A reset circuit is configured to set the latching relay to the reset state in response to an interruption of electrical power to the relay drive. In one embodiment, the reset circuit includes a supercapacitor configured to store a charge.
Data Source
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AI summary
An industrial process field device (100) includes an active component (111), a latching relay (120), a controller (110), a relay drive (122), and a reset circuit (140). The active component may be a sensor configured to sense a process parameter, or a control device configured to control a process of the industrial process. The controller (110) is configured to generate a switch signal, and the relay drive (122) is configured to set the latching relay (120) in one of a set state and a reset state based on the switch signal. The reset circuit (140) is configured to set the latching relay (120) to the reset state in response to an interruption of electrical power to the relay drive.