Antenna question

Hardware
1

Shelly Plus 1 UL relay inside a wall light fixture, (microwave on other side of wall) relay cannot be moved. Due to interference from appliances and/or the fixture, the WiFi connection is often lost. I tried a piece of aluminum foil between the relay and the microwave, which made no difference. Thoughts? Any way to add an antenna to this unit?

Note - I am often able to get the relay to reconnect to wifi by reconfiguring what WAP’s it is allowed to connect to (I use static IPs for everything.) This works MOST of the time. Eco mode is off but leaving it on or off makes no difference. It is also being used as a ble gateway to connect to some BLU devices but turning that on or off makes no difference either.

2

Did you earth the foil, possibly turning it into an even bigger antenna? I know the concept of a Faraday cage sounds attractive, but it has to be fully enclosed to be effective.

Microwaves obey the laws of light more than gravity according to my dad, when we bought our first microwave and mom was worried about all the torrent of bad microwaves rushing out, dropping to the kitchen floor, and cascading across the room when she opened the door, causing us foot cancer. This is what our neighbour had told her over the back fence. This was before COVID, MAGA, or even FaceBoob were invented. Some things never change!

Does it only fail when the microwave is actually heating (a critical door seal failure you should immediately fix as all microwaves should be contained inside the unit and none escape)? Just turned on and idle (possibly related and should be attended to urgently as there are thousands of volts floating around inside the cabinet, ready to spark and catch fire at even a hint of dust or moisture buildup)? Just turned off at the power point (definitely something else then), or the metal case on your microwave is reflecting interference to your Shelly from another device? Moving the microwave to another room or across the room make any difference? Turning it sideways (pointing the ‘death rays’ somewhere else)? Putting a small knot in the power cord change anything (sort of a coil filter that sometimes makes a difference at RF frequencies)?

Can you display the connection strength (in db) on your Shelly, or the router it is connected to? What is it? Does the error log show frequent WiFi disconnections, or device reboots?

Is MQTT configured correctly? Keepalive settings correct? There may be buffer space issues rather than connectivity issues at work here.

Unfortantely the only reliable way is the process of elimination. Remove anything that could possibly be causing interference and observe what happens when you add them back.

How many BLE devices do you have? How many devices overall? How many WiFi devices? Do they need to swamp THIS device? They use similar 2.4Ghz frequencies as WiFi and could be contributing to overall background noise. Are they also having reliable connectivity issues?

Just adding a larger antenna may not solve your problem that might be a strong source of interference will now swamp your device so it cannot connect, even intermittently.

Tools such as Android WiFi Analyser will identify neighbouring routers and busy channels. My neighbours have been caught out reconfiguring their routers for higher transmission power, swampimg the neighbourhood, and of course their own devices that cannot get a word in edgewise.

Check you also have the latest firmware on all your devices as often vendors fix things behind the scenes that are design oversights, and don’t mention them in their release notes.

Is your router firmware up to date? Does it support too many devices? Is the router system log showing frequent errors? How far away is your Shelly device? Do you have any repeaters?

3

First check if the microwave itself is to blame here, just unplug it and do dry tests how reliable the connection/ switching is without it being in the picture (bonus points for temporarily plugging in a lamp to visualize the switching). Background, know your enemy - are you fighting microwaves/ interference or ‘just’ bad reception (attenuation by the walls), as they need different fixes.

1 Like
4

Actually I think I resolved the issue, the nearest WAP WiFi threshold was -65db and that is very close to the signal strength at the relay. I’ve changed the threshold to -75db for that WAP, and will report back if that solved the issue.

5

That wouldn’t be safe. Since Shelly has esp32 gnd bonded to mains live, also antennas ground plane is at mains L.

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6

hm… that’s pretty (too) soon to disconnect. Among my 40+ wifi devices there are some happily live with wifi signal as low as -80, -85dB, and even -90dB works without problems.

In any way my experiences with this “forced” disconnect from AP/router point is unreliable - too many false disconnects. I turned it off on all my AP’s.

7

How could any router/ap force a connection of a device that is not connected? And do you have manual IP’s configured on the device or actually static IP’s (leases) from the DHCP server? :thinking:

To me it sounds the device is actually connected to WiFi but does not have a network connection/access. In this scenario you can force a reconnection from the router/ap by kicking the device (which will then usally reconnect again). :bulb:

Absolutely, over 100 ESPHome devices and they all a rock solid (including the weakest ones with -90db). :point_down:

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Your problems are probably home made. :clap: Why would you force disconnect your devices from an AP if no other AP is in range? :thinking:

1 Like
8

If the connection is lost only when the microwave oven is on, there’s the possibility of active or passive intermodulation, or simple RF desensitization due to front-end overload.

If the microwave oven is old, try to borrow another one for testing. The chassis might’ve developed corrosion at the junction of dissimilar metals, which is sometimes the source of the intermodulation interference.

If all else fails, consider using a product with a different frequency band. Unfortunately, it involves an outlay for a new integration infrastructure.

9

Note I reworded (clarified) the first sentence a little bit in my original post - regarding how I made it reconnect to the network - by changing what WAP’s it is allowed to connect to.

I have noticed that occasionally I am now unable to turn the light on or off from the light switch on the wall. There are three GFCI outlets and a wall switch in the same wall switch box, and one of the outlets I am also unable to test the cirtuit breaker on it. I am replacing all of those (all outlets, the switch and the covering plate) - as they are allpretty old - and will let you know if that resolves my issue. I only have the shelly up near the light fixture because there is no neutral by the wall switch/outlets. This is weird. I was thinking maybe the mains unswitched power line to the shelly is has power intermittently cutting out? I will report back -

10

Force disconnection is turned off for 2.4ghz on my network, the WAP’s just won’t accept connections below the stated level. 5Ghs does have the force disconnection turned on - as all the WAPs talk to each other etc. with a centralized controller (Omada). I went witrh Omada because of the great price but turned off the cloud capability years ago when I realized their headquarters & servers were in China. It works very well but had I known that about their severs way back when I would have gone with Unifi…

I have great coverage 5 WAPs in a 1,900 sq ft house, very carefully tuned on different channels so there are no issues (also no neighbor WiFi issues fortunately - there are signals from neighbors but they are weak).

Also, update - the ~25 year old GFCI light switch and three GFCI outlets were replaced and (and they were wired wrong - daisy chained) so that is corrected. Then I also now have the Shelly locked to the one WAP that is on the same side of the microwave as the shelly (shelly therefore in the middle between the microwave and that closest WAP). I did try to lock the Shelly to the two nearest WAPs but still had disconnection issues, so it is locked to only one WAP now. So far, so good - it has stayed connected for most of a day so far. The light fixture the shelly is in is also metal so to some small extent it and the embedded metal box in the wall must act together like a faraday cage. If this doesn’t work I may have to break a hole in the side of the metal box embedded in the wall behind the fixture, and have the shelly sitting outside of that box in the wall (possibly in another, plastic box). As it is an older home, there are many shelly’s in other metal switch boxes behind wall switches, but none of them have any issues. I’ll report back in a couple days…

11

Still the same issues. I have ordered a Shelly 1PM Gen 4 to use that instead to see if that will help as the power monitoring causes it to almost continuously send traffic (hopefully keeping the connection alive)…