Pulse Signal Recognition Circuit for PLC Scan Time
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Solution Overview
Problem
Conventional programmable logic controllers (PLCs) fail to recognize pulse signals input for short durations during a scan time without suspending the scan program, leading to increased scan time and limited input contact points due to the need for interrupt ports.
Innovation Solution
An apparatus with a signal delay unit, signal maintaining unit, signal transmission unit, control unit, and reset unit that maintains and outputs pulse signals as pulse maintaining signals, allowing input states to be stored without suspending the scan program, using optical couplers and D flip-flops to delay and store pulse signals until the end of the scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an interrupt port is used to recognize pulse signals, then pulse signal recognition is improved, but device complexity increases
Solution Approach 1:
The patent introduces a pulse signal input circuit as an intermediary component between the input terminal and the interrupt port. This circuit includes an optical coupler and a D flip-flop that work together to condition the pulse signal before it reaches the interrupt port, thereby improving pulse recognition while maintaining the existing interrupt port structure without adding complexity to the core processor
2Reliability
If the scan program is suspended to store pulse input data, then pulse signal recognition is improved, but productivity decreases
Solution Approach 1:
The patent implements preliminary action by using a D flip-flop to capture and hold the pulse signal state at the moment it occurs, before the scan program completes its current cycle. The pulse signal input circuit prepares the data in advance using the timing relationship between the pulse signal and the scan clock, so that when the scan program suspends briefly, the data is already ready for storage without requiring the scan to wait for signal processing
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that the scan program continues its execution flow without significant interruption. The pulse signal is captured during the scan cycle using the scan clock timing, and the brief suspension for data storage does not break the overall continuous scanning operation, allowing multiple pulses to be recognized across successive scan cycles without stopping the PLC's main functionality
3Reliability
If interrupt ports are added to recognize pulse signals, then the number of input contact points is limited, but adaptability decreases
Solution Approach 1:
The patent achieves universality by designing a pulse signal input circuit that can be applied to any input terminal of the PLC system. The circuit uses standard components (optical coupler, D flip-flop) that work with the existing scan clock and interrupt port infrastructure, allowing the same circuit design to be replicated across multiple input channels without requiring different hardware for each application, thereby maintaining adaptability while enabling pulse recognition
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
Enables recognition of pulse signals input for times shorter than the scan time without suspending the scan program, maintaining input states until the scan time terminates and storing data without increasing scan time or requiring additional interrupt ports.
Implementation Method 1
The plurality of pulse signal input circuits C1, ..., and Cn respectively include optical couplers C1-1, ..., and Cn-1, each of which maintains a non-conducting state and then is conducting when a signal is input, thereby outputting the input signal.
Implementation Method 2
when a rising edge of a scan clock is detected, the signal maintaining unit maintains and outputs the input pulse signal as a pulse maintaining signal... the control unit stores the pulse maintaining signal in a pulse signal storage area as pulse input data
Data Source
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AI summary
The present disclosure relates to an apparatus for recognizing a pulse signal, and more particularly, to an apparatus for recognizing a pulse signal, which maintains the pulse signal being input for a scan time until an end time point of the scan time, and stores the pulse signal in a pulse signal storage area as pulse input data. The apparatus for recognizing a pulse signal according to one embodiment of the present disclosure includes a signal maintaining unit (120) configured to maintain and output the pulse signal, which is input for the scan time, as a pulse maintaining signal; a signal transmission unit (130) configured to receive the pulse maintaining signal from the signal maintaining unit and transmit the input pulse maintaining signal based on a transmission control signal; and a control unit (140) configured to output the transmission control signal to the signal transmission unit (130) to receive the pulse maintaining signal, and store the received pulse maintaining signal in a pulse signal storage area as pulse input data.