Reliability and safety are the core and most fundamental functions of automated equipment. User-friendly and efficient human-machine interaction is the primary manifestation of the value of the equipment. These aspects best reflect the designer’s skills. Especially in electrical systems, whether in scheme design, program coding, or circuit design, the goal should be to achieve safe and reliable operation and efficient human-machine interaction.

How should we understand reliability and safety? Reliability means the equipment can operate stably, working 24/7 without various faults. If a device has major issues frequently and minor problems constantly, it is absolutely unacceptable. Safety means that under any circumstances, the equipment can stop quickly to prevent accidents and damage to materials or components.

How to achieve efficient human-machine interaction? It means that no matter how complex the equipment is, the operation should be simple, allowing frontline workers to quickly understand it. When issues arise, the equipment should display fault information, enabling workers to quickly identify and resolve the problem. Even if workers cannot solve the issue, the designer should be able to immediately determine the fault point from the feedback on-site.

Achieving these goals seems simple, but it is actually a long process that requires lifelong learning, continuous thinking, and experience summarization. Therefore, many people who think they understand PLC by just creating a few start-stop circuits and operating a few cylinders believe PLC is simple, which is quite amusing.

In fact, during the design and selection phase, many issues should be fundamentally addressed. Many devices have no major problems but constant minor issues, mostly due to problems in the design phase.

• Directly cutting off the power when inverters or servos fail.
• Directly cutting off the power with an emergency stop button.
• Equating stop and emergency stop functions.
• Using 220V for switches and buttons directly operated by humans.
• Using proximity switches for limit switches.
• Using normally open contacts for safety signals.
• Lack of state memory, making shutdown and startup processes cumbersome.
• Not considering EMC (Electromagnetic Compatibility).

What are your thoughts on these issues?