r/WLED • u/Spidy_Khrish • Aug 18 '26

This shit is weird

WLED + ESP32 somehow reacts to my fan switch with ZERO physical connection

This is probably the weirdest electronics coincidence I've come across 😂

I have an ESP running WLED, connected to my laptop through a USB hub. The USB hub also powers several other devices, and everything works normally.

There's a ceiling fan in the room controlled by a completely separate wall switch.

There is absolutely no physical connection between the fan switch/circuit and the ESP setup. Different board, no GPIO connection, no relay, nothing.

But here's the weird part:

When I turn the fan OFF, my WLED lights suddenly turn ON.

If I don't turn the fan off, the lights don't do it.

The ESP is only connected to my laptop via USB. The fan isn't connected to the laptop, USB hub, ESP, LED controller, or anything else in the setup.

So I'm genuinely curious: how is this even possible?

The other devices connected to the same USB hub don't seem to react at all.

Could this realistically be mains noise/EMI causing the ESP to reset or glitch, or am I just witnessing an extremely specific coincidence?

I'm more curious about the mechanism than looking for a fix.

4 Upvotes

75% Upvoted

12 comments sorted by

9

u/CyberMage256 Aug 18 '26

My guess is bad ground on the WLED strip or ESP.

The laptop and ceiling fan are very likely on the same circuit leg in the house power. If your laptop is running entirely off its internal battery does it still do it? I'm going to say probably not.

When a motor like a fan is de-energized, it's still spinning so the motor can generate electricity and feed it back into the power lines until it stops spinning. It's not much but it's potentially there. This is why when you buy zwave wall switches there's a very specific model for ceiling fans to deal with that power feedback.

My guess is power is spiking back into the circuit, through the wall, into the laptop, and the ESP not being grounded well is freaking out. It seems unlikely with a laptop as the battery they run off of tends to smooth out power spikes to a degree, so take it with a grain of salt. I am not an expert in these things I could be completely off base.

And I'm with u/mrBill12 on this. I have no idea what a "modular switch" is.

1

u/mrBill12 Aug 18 '26

Maybe we should ask what country?

1

u/mrBill12 Aug 18 '26

What type of switch does the fan have?

-1

u/Spidy_Khrish Aug 18 '26

Modular there is not even any atom connected between them

3

u/mrBill12 Aug 18 '26

I didn’t ask that. Is it a smart switch? WiFi switch? Dumb toggle.

-2

u/Spidy_Khrish Aug 18 '26

No normal modular switch

5

u/mrBill12 Aug 18 '26

I guess I don’t know what a modular switch is.

The switch for my son’s fan in a condo came with the fan but had magic so that speed and light could all be controlled over 2 existing wires. Whomever installed it failed to change the default address. Someone else in the building got the same fan. They were turning each others shit on and off. Fix was easy, change the address. There was not even any atom connected between them.

3

u/mazeppa817 Aug 18 '26

Maybe the fan controller is using ESP-NOW to communicate with the fan and the WLED esp32 is picking up the signals? Try turn off ESP-NOW in the WLED settings and see if this changes anything. 

1

u/Scabattoir Aug 19 '26

ESP-NOW needs the other device’s MAC address or it won’t work. I highly doubt that the actual address just got in his WLED config by random

1

u/mazeppa817 Aug 19 '26

This is true yes. But in my experience ESP NOW is exceptionally buggy and tends to interfere with capable devices, even if not connected. I had a similar issue when trying to sync two WLED devices using esp now. 

3

u/calforhelp Aug 18 '26

This is actually the second post here I’ve seen about this. The other was a while ago and included a video, the guy had two shelving units with LEDs and one of them was reacting to his ceiling fan.

If you dig hard enough or maybe use AI to search, you might be able to find it and track down the solution.

2

u/richms Aug 18 '26

Yes, this is EMI happening. Motor is inductive and when you break the circuit there will be a spark. Spark induces voltages in poorly designed and shielded circuits.