Single-Chip PLC Design for Low-Cost Machine Control
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Solution Overview
Problem
Highly reliable and stable programmable logic controllers (PLCs) are expensive, making them costly for controlling simple machine actions, which increases manufacturing costs.
Innovation Solution
A cost-effective PLC design utilizing an Intel MCS-51 series SOC single-chip as the core, combined with a DC power module, I/O module, relay output module, and pulse output module, with a system program that allows for easy programming and control of machines, while maintaining reliability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive high-reliability PLCs are used to control simple machine actions, then reliability and stability are improved, but manufacturing costs increase
Solution Approach 1:
The PLC system is divided into functional modules: a single-chip microcomputer core module (Intel MCS-51 series) and separate I/O expansion modules. This segmentation allows the core controller to be simple and inexpensive while adding reliability through modular design with dedicated power modules, I/O modules, and control modules that can be independently optimized and replaced.
Solution Approach 2:
The patent combines multiple functions into an integrated PLC system: the single-chip microcomputer integrates CPU, memory, and basic I/O; power modules combine voltage regulation and protection circuits; I/O modules integrate multiple input/output channels. This merging reduces overall system cost while maintaining reliability through functional integration at appropriate levels.
2Ease of manufacture
If simple low-cost controllers are used, then manufacturing costs are reduced, but reliability and stability deteriorate
Solution Approach 1:
The patent uses inexpensive Intel MCS-51 series single-chip microcomputers as the core controller, which are low-cost and widely available. Rather than using expensive industrial-grade processors, the system accepts the limitations of consumer-grade components and compensates through robust software design, modular architecture, and protective circuitry in the power and I/O modules.
Solution Approach 2:
The power module includes voltage regulation circuits, reverse polarity protection, and over-current protection that cushion against power supply failures before they can damage the sensitive single-chip microcomputer. This beforehand protection ensures reliable operation despite using inexpensive components.
3Ease of manufacture
If a single-chip processor is used instead of traditional PLC architecture, then manufacturing cost is reduced, but device complexity must be managed
Solution Approach 1:
The single-chip microcomputer is designed to perform multiple functions: digital I/O control, analog-to-digital conversion, pulse generation for motor control, and communication protocols. By making the core processor universal and multi-functional, the system reduces the need for separate dedicated circuits, thereby managing complexity while maintaining low cost.
Solution Approach 2:
The patent introduces intermediate I/O modules that mediate between the simple single-chip microcomputer and the complex external world of sensors, actuators, and communication interfaces. These intermediary modules handle protocol conversion, signal conditioning, and isolation, shielding the core processor from complexity while expanding system capabilities.
Data Source
AI summary
A PLC includes a single-chip, a relay output module, an I/O module, a pulse output module, a relay, and a servo motor. The single chip includes a single-chip timer, a hardware watchdog, a 11.0592M crystal, and an A/D converter module. A system program is burned into an EEPROM of the single-chip. The relay connected to the relay output module. The servo motor is connected to the pulse output module. The system program includes a programming module and a control module. The programming module includes a main function and a function subroutine library, and the main function calls the subroutines of the function subroutine library. The control module scans the input signals from the I/O module during predetermined period, and then generates output signals according to the control commands generated by the programming module, to control output of the relay output module and the pulse output module.