MSB or FA-DUINO has small relay inside.

Sometimes the included relay is not enough to turn on and off a large load. At this time, you need to additionally use a large extra relay.

To remove the spark when the extra relay is turned on/off, we recommend using a surge suppressor.

Look this power measurement result without a surge suppressor

Can see this spark signal on power line when external Relay turn on and off.

If a surge suppressor is added like this…

… the surge will gone.

If you don't use surge suppressor looks like working fine. but huge demage goes to main circuit, finally make a problem.

I saw many user's control panel don't use Surge suppressor, they said “my machine often stop or reboot. I don't know why!”.

Surge suppressor price is very cheap, and very useful at your circuit.

refer this other company user's manual.

This is EATON's PLC manual. They said same story.

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