How to prevent interference with industrial servo DI/DO signals?

Servo digital input (DI, such as limit, enable) and output (DO, such as alarm, ready) signal anti-interference design must prevent malfunctions and ensure drive capability. Audiotech's protection measures:

For DI signals:

1) Use optocouplers or digital isolators for electrical isolation.

2) Connect a series resistor (e.g., 1kΩ) at the optocoupler input for current limiting and a TVS (ESD5V0D3B) in parallel to protect against transient overvoltage.

3) For slowly changing signals, add an RC filter or Schmitt trigger at the optocoupler output.

For DO signals:

1) If driving external relays or other inductive loads, a freewheeling diode or RC buffer circuit must be connected in parallel across the load.

2) Connect a series resistor or ferrite bead (PBZ series) at the DO output port to slow down edge interference and reduce radiation. All DI/DO cables should be shielded, with the shield grounded at the driver end.

Through design, the DI/DO circuit can withstand ±1kV EFT interference and ±4kV ESD, ensuring reliable operation in industrial environments.