How should the strong and weak current wiring be isolated on the motherboard of an HMI (Human Machine Interface)?

Implementing strong and weak current isolation routing on the HMI motherboard is the fundamental measure to prevent interference coupling. Strong current refers to high-voltage, high-current lines such as AC power supplies, DC power supplies, and motor drives; weak current refers to low-voltage, small-signal lines such as those of the MCU, memory, sensors, and communication interfaces. The primary principle of isolation is zoned layout: clearly define strong and weak current zones on the PCB, leaving sufficient spacing between them, typically recommended to be at least 1cm, and physical isolation can be achieved using ground lines or slots. When routing, strong and weak current traces should be separated as much as possible; for example, strong current should run on the top layer, weak current on the bottom layer, and isolated by a ground plane.

If traces must be run on the same layer, sufficient spacing must be ensured; spacing rules can refer to voltage difference and creepage distance requirements. Long parallel runs of strong and weak current lines are strictly prohibited. If crossing is unavoidable, they should be perpendicular to minimize coupling area. Strong current lines, especially power loops in switching power supplies, should be kept short and wide to reduce loop area and parasitic inductance. Weak current signal lines should be routed as close to the ground plane as possible, providing a complete mirrored return path. At the power inlets of both high-voltage and low-voltage areas, ferrite beads, such as the PBZ2012 series, are used for isolation and filtering. Through strict layout zoning and wiring rules, and by utilizing the isolation filtering devices from Eternit Electronics, mutual interference between high-voltage and low-voltage circuits can be minimized.