Control Pneumatic Cylinder with Arduino: MOSFET Circuit Design

This segment demonstrates implementing a state machine (Finite State Machine) for controlling cylinder movement through sequential operations. The instructor shows how to use SM (Special Memory) bits to represent different states (M0-M9) for each operation phase. Key concepts include: using RST and SET instructions for state transitions, implementing time delays using timers (T0) between position changes, and creating state transitions based on position comparisons. The state machine approach provides structured, reliable control of sequential operations with clear entry and exit conditions for each state.

A finite state machine is a programming approach where a system can exist in one of several distinct states, each performing a specific function. In Arduino programming, this is implemented using the switch-case command structure. The system transitions between states based on conditions, with each state doing exactly one thing and nothing else. This approach provides a clear, organized way to manage complex systems with multiple possible scenarios.

A finite state machine (FSM) is a sequential circuit that transitions between discrete states based on inputs, where the Arduino implementation uses a clock signal to trigger state changes and a control signal to determine the direction of state transitions, demonstrated through a 4-state machine that cycles through states A, B, C, D in forward or reverse order depending on the control input.

This program demonstrates a complex state machine in the Arduino simulator. Four LEDs are controlled by two buttons (pins 8 and 9) with corresponding memory variables. The simulator shows how different button combinations produce different LED patterns: when only button A is pressed, LEDs cycle in one direction; when only button B is pressed, LEDs cycle in the opposite direction; when both buttons are pressed, LEDs flash on and off rapidly. The visual simulation allows users to observe the complete state machine behavior in real-time.

State machines provide a powerful approach for managing complex behaviors in Arduino programming. Unlike traditional spaghetti code where all instructions are mixed in a single loop, state machines divide behavior into multiple distinct loops (states), with only one active at any time. This approach is essential for applications like ovens, measurement devices, and multi-level menus. The fundamental process involves first designing a complete state diagram on paper, then implementing it using switch-case structures in code. Each state contains its own loop that executes specific behaviors, making the system more organized, maintainable, and easier to extend.

Arduino microcontrollers are unsuitable for industrial control applications due to several critical limitations: they require 5-9V DC power (conflicting with industrial 12V+ standards), lack DIN rail mounting capability, have exposed circuitry vulnerable to dust and debris, cannot communicate with industrial protocols like Profibus/Profinet, and lack backup programming capabilities. In contrast, PLCs (Programmable Logic Controllers) are specifically designed for industrial environments with DIN rail mounting, enclosed circuitry, integrated industrial communication protocols, higher power outputs, and expandable I/O capabilities, making them the appropriate choice for industrial automation despite being more expensive and less programmable than Arduino.

This comprehensive section covers the complete journey of Arduino-based industrial PLCs from conceptual introduction to detailed hardware implementation. The system utilizes genuine Arduino Leonardo and Mega 2560 boards as the processing core, wrapped in industrial-grade enclosures featuring DIN rail mountability, 24V compatibility, and isolated relay outputs capable of handling 240V at several amps. Key hardware components include: main enclosures with labeled relay outputs and I/O pins; genuine Arduino boards providing the processing platform; switch-mode power supply modules with ceramic fuses and industrial-rated capacitors; and I/O boards containing Omron relays, opto-isolators, and signal conditioning circuitry. Communication interfaces span I2C, SPI, MODBUS, RS485, and RS232, with pull-up modules available for I2C bus termination. The modular design allows expansion through additional I/O boards connected via ribbon cables, enabling scalable I/O capacity. Safety features include isolated relay outputs with individual electrical separation, screw-terminal connections for high-voltage applications, and proper creepage clearance between relay contacts and control logic. Detailed component analysis reveals opto-isolators (D207/D271 series) providing electrical isolation; STMicro LM2902 operational amplifiers handling signal conditioning; and transistor driver circuits essential for driving relay coils rated for 5A at 240V AC. The boards feature screw terminals for high-voltage connections to prevent vibration-induced disconnection. DIN rail mounting with standoff hardware secures boards against mechanical vibration. CE approval confirms compliance for industrial installations. The design philosophy prioritizes reliability through component selection and mechanical design considerations for industrial environments where temperature fluctuations, electrical noise, and mechanical stress are common operational challenges.

Arduino is designed as an educational training platform for testing and learning, not for industrial environments, while PLCs (Programmable Logic Controllers) are specifically engineered for industrial applications with robust hardware including isolation for 24V systems, noise filtering, and high-voltage control capabilities; however, the microcontroller itself (such as ATmega328 from Microchip) can be extracted and used in industrial projects with proper isolation components like optocouplers and filters.

Controllino is an industrial-grade PLC (Programmable Logic Controller) that allows programming using Arduino IDE and other open-source tools, providing the reliability, safety certifications, and robustness of traditional industrial PLCs while maintaining the ease of use and accessibility of Arduino programming. Unlike standard Arduino boards, Controllino features 4000V ESD protection, circuit protection against overloads and surges, real-time clock functionality, and multiple input/output configurations (digital, analog, relay outputs up to 16A at 230V), making it suitable for industrial automation applications where reliability and safety are critical.

This video demonstrates a professional Arduino-based PLC (Programmable Logic Controller) that addresses key limitations of standard Arduino boards for industrial automation applications. The mini PLC features 24V industrial power input with DC-DC conversion, RS-485 communication for industrial networking, optically isolated digital inputs and outputs (0-24V), and analog inputs supporting both 0-10V and 4-20mA sensor signals. All inputs are protected against voltage surges with transient suppression diodes. The platform maintains Arduino compatibility, allowing developers to leverage existing Arduino libraries and programming knowledge while achieving industrial-grade reliability and performance suitable for factory automation environments.

This video demonstrates how to achieve proportional control of pneumatic cylinders by using two separate air sources (such as two compressed air tanks) connected to each side of the cylinder, which eliminates the creep problem caused by unequal surface areas in standard cylinders; the system uses solenoid valves to hold position and a servo-controlled isolation valve to regulate air flow for smooth deceleration curves, though the Arduino microcontroller requires protection against back EMF spikes from the solenoid coils.

Proportional pneumatic valves use variable voltage signals (typically 0-10V) to continuously adjust valve position, enabling precise control of cylinder speed and position. Unlike traditional on/off valves that only have discrete positions, proportional valves allow the cylinder to move at any speed between fully open and fully closed based on the applied voltage level. When combined with a linear position transducer (potentiometer) that converts mechanical position into an electrical signal, these systems enable accurate position feedback and control in pneumatic automation applications.

Proportional pneumatic control systems use valves that can vary flow rates continuously rather than just opening or closing completely, enabling precise control of actuator speed and position. Unlike discrete systems that only provide full open or full closed states, proportional valves respond to analog signals (typically 0-10V, 4-20mA, or PWM) to create intermediate flow rates. This allows for smooth acceleration, deceleration, and variable speed operation of pneumatic cylinders, which is essential for applications requiring dynamic motion profiles such as robotic systems, automated machinery, and precision positioning equipment. The key advantage is the ability to achieve any desired speed profile by adjusting the signal level, rather than being limited to fixed speed steps.

This video demonstrates proportional control of a pneumatic cylinder using a PID controller, where a mono-stable proportional valve (53) regulates cylinder position by varying electrical input voltage (0V for retraction, 10V for extension, 5V for stop), with a linear potentiometer providing position feedback and a PID controller with proportional gain of 0.1 achieving critically damped response while maintaining a small steady-state error of approximately 0.01V.