Safety Switching Device Start Mode Selection via Digital Sampling
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Solution Overview
Problem
Existing safety switching devices face challenges in efficiently and reliably selecting different start modes after their safety function has been triggered, often requiring multiple devices with varying configurations, which can be cumbersome, space-consuming, and costly, and may lead to confusion and reduced reliability in detection.
Innovation Solution
A safety switching device with a reset input and an evaluation circuit that uses digital sampling to detect start signals from a sequence of sampled values, allowing for flexible detection of various signal types, including voltage levels, edges, and clocked signals, and includes features like biasing and decoupling to enhance reliability and simplicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple safety switching devices with different start modes are provided, then different start modes can be supported, but device complexity and space requirements increase
Solution Approach 1:
The evaluation circuit is designed to universally detect multiple types of start signals (voltage level, voltage edge, and clocked signals) through a single device. The circuit uses a sampling device that can process different signal types by configuring the sampling parameters, eliminating the need for multiple specialized devices and reducing overall system complexity.
2Adaptability or versatility
If multiple safety switching devices with different start modes are provided, then different start modes can be supported, but cost increases
Solution Approach 1:
By designing a single evaluation circuit that can detect multiple start signal types through configurable sampling parameters, the invention eliminates the need to manufacture and stock multiple different device variants. This universal approach reduces manufacturing costs, inventory requirements, and distribution complexity while maintaining full functionality support.
3Ease of operation
If analog detection is used to detect start signals, then detection can be performed, but reliability is reduced due to temporary deviations
Solution Approach 1:
The sampling device performs preliminary sampling of the signal at the reset input over a defined sequence of sampled values before making a detection decision. This preliminary action allows the circuit to distinguish between temporary deviations and actual start signals by evaluating multiple samples, thereby improving reliability while maintaining ease of operation.
Solution Approach 2:
The evaluation circuit uses feedback from the sequence of sampled values to determine whether a valid start signal is present. By continuously sampling and evaluating the signal characteristics against defined criteria, the circuit provides reliable detection that is immune to temporary disturbances, while still maintaining simple operation through automated evaluation.
4Reliability
If the sampling sequence is extended to improve detection reliability, then reliability increases, but restart time increases
Solution Approach 1:
The sampling device dynamically configures the sampling parameters including the number of samples and sampling rate based on the specific start signal type being detected. This dynamic adaptation allows the system to use shorter sampling sequences for reliable signals while using longer sequences only when necessary, optimizing the balance between detection reliability and restart speed for different operating conditions.
Data Source
Figure 1
Figure 2~5
AI summary
The device (1) has a reset input (IN) for starting the device after triggering a safety function of the device, where the device is operable in various start modes. An evaluation circuit (2) is connected with the reset input to detect application of a start signal. The circuit selects a start mode for the device in correspondence with the detected start signal. The circuit comprises a sampling unit (4) for sampling the start signal at the reset input and detecting a sequence of sample values. The circuit detects a voltage level, a voltage slope or a clocked signal as the start signal.