CAN Bus Active Terminator With Automatic Relay Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing CAN bus termination methods rely on user memory and are often complex and expensive, as they require manual switching of terminating impedances when extensions are added, leading to potential mistermination and system degradation.
Innovation Solution
A data bus arrangement with an electronic relay that automatically connects and disconnects termination impedance across the high and low data conductors based on the presence of a CAN bus extension, using a photoMOS relay circuit to ensure proper termination without user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual switching of terminating impedances is used, then the system can be terminated properly when extensions are added, but the complexity and cost increase due to requiring user intervention and memory
Solution Approach 1:
The termination arrangement automatically detects when a CAN bus extension is connected and switches the terminating impedance accordingly without requiring user intervention. The system monitors the bus state and self-adjusts the termination configuration, eliminating the need for users to remember to manually switch terminators while maintaining proper termination reliability.
2Ease of operation
If automated termination arrangements are used, then user intervention is eliminated, but the complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical switching mechanisms with a simple electronic relay circuit controlled by voltage detection. Instead of using complicated automated switches or microcontrollers, the system uses the inherent voltage changes on the CAN bus to control a relay, achieving automated termination with minimal added complexity.
Solution Approach 2:
The relay circuit acts as an intermediary between the CAN bus voltage state and the terminating impedance. It monitors the voltage on the bus and automatically switches the termination configuration based on whether an extension is detected, providing automated operation without requiring complex control logic.
3Reliability
If terminating impedances are manually plugged in or switched, then proper termination can be achieved, but system degradation occurs due to user error and forgetfulness
Solution Approach 1:
The terminating impedance is pre-configured and automatically activated when needed without requiring user action. The system is designed so that the termination is already in place and only needs to be switched on or off based on bus conditions, eliminating the time users would spend manually plugging in or switching terminators while maintaining accurate termination.
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 solution ensures automatic and reliable termination of the CAN bus, maintaining system performance by adjusting impedance dynamically with the connection of extensions, eliminating the need for manual switching and reducing complexity and cost.
Implementation Method 1
The electronic relay may comprise a photoMOS relay circuit
Data Source
AI summary
A terminator for a CAN bus includes an electronic relay and a termination impedance. The electronic relay has first and second control input conductors and switched output conductors. The electrical connection between the switched output conductors is normally closed. The first control input conductor is connected to the power conductor and the second control input conductor is connected to a fifth terminal of the first CAN bus connector. The termination impedance is connected in series at the end node of the CAN bus with the switched output conductors across the high data conductor and the low data conductor. By this arrangement, the termination impedance is effectively connected across the high data conductor and the low data conductor at the end node of the CAN bus until an extension of the CAN bus is plugged into the first CAN bus connector. When an extension of the CAN bus is plugged into the first CAN bus connector, the fifth terminal of the CAN bus connector is connected to the ground conductor. This actuates the relay and opens the switched output conductors.