Card Reader Solenoid Chopper Control for Overheating Prevention
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Solution Overview
Problem
Card readers with IC contact blocks experience coil breakage due to prolonged solenoid energization, leading to overheating during continuous communication with IC chips.
Innovation Solution
Implement a method that includes an IC contact holding step, a holding voltage lowering step using chopper control, and a duty cycle setting step to determine and store the smallest duty cycle for effective voltage reduction, preventing overheating and coil breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the solenoid is continuously energized to keep the IC contact block in contact with the card surface, then the IC contact block maintains stable contact with the card, but the solenoid overheats and the coil may break due to prolonged energization
Solution Approach 1:
The patent applies periodic action by implementing chopper control that repeatedly turns on and off the energization to the solenoid. This periodic energization maintains the IC contact block in contact with the card surface while reducing the average power consumption and preventing overheating of the solenoid coil, thus resolving the contradiction between contact stability and temperature control
Solution Approach 2:
The patent changes the energization parameter from continuous constant current to pulsed current with variable duty cycle. By adjusting the duty cycle ratio (the proportion of on-time within each cycle), the system maintains sufficient contact force while reducing overall heat generation, thereby solving the overheating problem while preserving contact reliability
2Temperature
If chopper control is performed with a low duty cycle to reduce overheating, then the solenoid temperature is controlled, but the IC contact block may not be reliably held in contact with the card surface
Solution Approach 1:
The patent implements feedback by detecting whether the IC contact block is actually held in the contact position and using this information to adjust the duty cycle. The system determines the minimum duty cycle required to maintain contact and uses this feedback to optimize the energization control, ensuring reliable contact while minimizing overheating
Solution Approach 2:
The patent applies dynamics by making the duty cycle adjustable and adaptive rather than fixed. The system dynamically determines the appropriate duty cycle based on actual contact conditions, allowing the energization parameters to change in response to system state, thus maintaining contact reliability while controlling temperature
3Duration of action of stationary object
If the duty cycle is set too low to prevent overheating, then the solenoid is protected from breakage, but the IC contact block cannot be reliably held in contact position
Solution Approach 1:
The patent applies self-service by enabling the system to automatically determine and store the minimum required duty cycle through self-testing. The card reader autonomously performs tests to find the optimal duty cycle value that maintains contact while preventing overheating, eliminating the need for manual configuration and ensuring both contact reliability and solenoid protection
4Duration of action of moving object
If continuous energization is used to maintain contact during repeated communication or card retention, then the IC contact block remains in contact position, but the solenoid coil breaks due to prolonged overheating
Solution Approach 1:
The patent applies periodic action by using chopper control to intermittently energize the solenoid instead of continuous energization. This periodic energization pattern reduces the cumulative heat buildup in the coil over extended periods while maintaining contact position, thereby preventing coil breakage during prolonged operation such as repeated communication or card retention
Solution Approach 2:
The patent changes the energization parameter from continuous to pulsed with optimized duty cycle. By adjusting the duty cycle to the minimum value required to maintain contact, the system reduces the average power dissipation and heat generation in the solenoid coil, extending its operational lifespan while maintaining contact duration
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 method effectively lowers the solenoid's effective voltage through chopper control, inhibiting overheating and preventing coil breakage while maintaining contact with the IC chip, thereby extending the solenoid's lifespan.
Implementation Method 1
a solenoid that moves the IC contact block toward a card conveyance path
Implementation Method 2
a compressed coil spring that retracts the IC contact block from the card conveyance path
Data Source
AI summary
A method for control of a card reader is provided. A control unit of a card reader performs an IC contact holding step for continuously energizing a solenoid to press an IC contact block against a card, and a holding voltage lowering step in which a state in which the IC contact block is pressed against the card is kept by performing chopper control of repeatedly turning on and off energization to the solenoid. The control unit performs the chopper control with a duty cycle being lowered stepwise. A duty cycle one stage before a duty cycle that is first determined to be a duty cycle in which the IC contact block is not held in a spring contact position (that is, a sensor is turned off) is stored in a storage unit. Thereafter, chopper control is performed by using the duty cycle stored in the storage unit.