wifi switch schematic I'm using NODEMCU and SSR modules to turn on / off the lamps with WiFi. Nodemcu uses I = 80mA and V = 5v as its input current and voltage (Vin pin). It worked without any problems with a single lamp on my desk. When I implemented the whole device behind a light switch and connected the ac wires to the SSR module, there were some problems. The WiFi switch works fine alone and also, I can control it via WiFi. But when I hit another switch next to it which is not WiFi enabled, it affects the WiFi switch.

For example, when I want to turn on a lamp and hit its switch (which is not WiFi enabled), the lamp turns on and subsequently, the lamp which has a WiFi enabled switch turns off and on randomly. I think because nodemcu needs 80mA current, it's sensitive to power swing. and I can't use sleep mode because if I use it, WiFi will be disabled and as I want my device to be in station mode, it would cause problems.

I tried different capacitors for Vin pin from 0.1 uF to 470 uF !! but none of them helped and still, when I turn on some other lamp, it has a bad effect on my device.

What is the problem and how can I solve it?

  • \$\begingroup\$ Please add schematic.. \$\endgroup\$
    – Electron
    Jan 6, 2019 at 14:27
  • 1
    \$\begingroup\$ I added the schematic. \$\endgroup\$ Jan 6, 2019 at 14:51
  • \$\begingroup\$ from where you are giving power to node mcu? \$\endgroup\$
    – Electron
    Jan 6, 2019 at 14:58
  • \$\begingroup\$ I use a huawei charger and a usb to ttl module to power my device. \$\endgroup\$ Jan 6, 2019 at 15:04
  • \$\begingroup\$ Really? What role does the USB TTL adapter have in the power? Does it have a distinct regulator or only the USB chip? They are not really are to supply power. \$\endgroup\$ Jan 6, 2019 at 16:56

1 Answer 1


Put a 100 ohm resistor across the SSR input (3/4). They are quite sensitive and can trigger from even a small amount of coupled energy. The 100 ohms will shunt that away.

  • \$\begingroup\$ I did it, but it got worse. Now, not only it is affected by turning some other bulbs on, but it also blinks! \$\endgroup\$ Jan 7, 2019 at 8:38
  • \$\begingroup\$ I used the Nodemcu with an electromechanical relay and everything's ok now. So the problem is really due to SSR's sensitiveness. The noise has a bad effect on it. How can I solve this?!! \$\endgroup\$ Jan 7, 2019 at 12:39

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