When you design PCB for Industrial Automation applications. Please refer these examples.

1. Connectable Terminal Block : Easy to replace board at the field
2. Use ZNR : It is for surge protect.
3. Use Swiching Regulater : It is good for heat defense. Don't use linear Regulater (Such as LM7805).
4. Display Information : it is usually invisible because the PCB is placed in the control box, But 7-segment display or LED are good for mainternance.

This PCB look like little bit expensive but it is good design.

• Use 4 layer PCB : It is the best for noise defense. Inner layer are all VDD and VSS. these layer will useful noise defense.
• Use DC/DC and opto-coupler : It is isolation design.
• Large size PCB : It prevents the board temperature rising.

Look at this PCB. This is one of our customer custom design. It is example good PCB.

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