Relay Socket Assembly Using PTC Reverse Connection Protection
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Solution Overview
Problem
Existing relay assemblies are prone to damage due to incorrect relay insertion, causing short circuits and potential harm to the relay coil and printed circuit board traces, as they lack effective protection against improper orientation.
Innovation Solution
Incorporation of a positive temperature coefficient thermistor (PTC) between the relay socket and power source to prevent overcurrents in case of incorrect relay orientation, utilizing a polymer-based PTC material with conductive fillers and additives for enhanced sensitivity and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a relay is designed with symmetrical pins for ease of installation, then the ease of operation is improved, but the reliability deteriorates due to risk of incorrect insertion causing short circuits
Solution Approach 1:
A PTC thermistor is introduced as an intermediary protective component between the power source and the relay socket. This thermistor acts as a mediator that allows normal current flow during correct operation but blocks excessive current during incorrect relay insertion, thus protecting the relay and circuit board without affecting the symmetrical pin design
Solution Approach 2:
The PTC thermistor provides beforehand cushioning by being pre-installed in the circuit to cushion against the harmful effects of incorrect relay insertion. When reverse polarity or short circuit occurs due to wrong insertion, the PTC thermistor rapidly increases its resistance to limit current, preventing damage before it occurs
2Reliability
If a PTC thermistor is added to protect against reverse connection, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The PTC thermistor provides self-service protection by automatically responding to overcurrent conditions without requiring external control circuits or additional components. When excessive current flows due to reverse connection, the thermistor's temperature increases and its resistance increases accordingly, automatically limiting the current and protecting the circuit
Solution Approach 2:
The PTC thermistor utilizes parameter changes in its electrical resistance based on temperature. Under normal operating conditions, the thermistor maintains low resistance for minimal voltage drop. When reverse connection or overcurrent occurs, the temperature rise causes the resistance to increase dramatically, providing protection without adding complex control logic
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
Prevents damage to relays and connected components by blocking overcurrents when relays are inserted incorrectly, enhancing functionality and safety.
Implementation Method 1
a positive temperature coefficient thermistor (PTC) for reverse connection protection
Implementation Method 2
utilizing a polymer-based PTC material with conductive fillers and additives for enhanced sensitivity and protection
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Disclosed are electrical relay assemblies including a positive temperature coefficient thermistor (PTC) for reverse connection protection. In some embodiments, a relay assembly includes a relay socket receiving a relay, a power source connected to the relay socket, and a positive temperature coefficient thermistor (PTC) connected between the relay socket and the power source.