I have the following problem: I have a WiFi electronic device in my kitchen to automate the lights using relays (made by me).

It is based on a Wemos D1 mini microcontroller and the PSU is a Hi-Link (220 V to 5 V).

The problem is that sometimes when I open the microwave door, turn on a stove (it has an electric igniter), or turn off the kitchen extractor fan, the device resets. It's like turning it off and back on again in a few milliseconds. This only happens with the devices I mentioned and only in the kitchen.


enter image description here

What could be wrong?

  • \$\begingroup\$ Any number of things could be wrong. We have no way to see how you designed your device or made the connections. Please post schematics, PCB design and photos to see the device. \$\endgroup\$
    – Justme
    Sep 15 at 20:17
  • \$\begingroup\$ @Justme I added a schematic to the original post, hope it helps \$\endgroup\$
    – vazquezjm
    Sep 15 at 21:01
  • 1
    \$\begingroup\$ Those are not schematics. That looks more like a block diagram or wiring diagram. Of the mains and supply wires only, not the other wires. So you don't have earthing on any device, even on the microwave? And you don't have the filter components that are suggested for the power supply module? What does the "wifi controlled device" do and how does it connect to outside world, it was supposed to drive some relays? \$\endgroup\$
    – Justme
    Sep 16 at 5:12
  • \$\begingroup\$ EMI issue. Either your PSU is crap for not suppressing it or there is a schematic or layout problem on your WiFi controlled device. Please post schematic and layout of it. \$\endgroup\$
    – winny
    Sep 16 at 12:13

1 Answer 1


It appears that switching transients are the root cause for the microcontroller getting reset.

You need to use a mains EMI filter before the power supply.


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