I was thinking how I can bypass the sensor using existing switch on the wall when I need to switch power on to enable the sensor. Obviously, it was lack of thinking on my side

The sensor need separate power connection, right? So, I can tap the power from the ceiling as shown by purple connection. The sensor will not bother if the wall switch is ON or OFF. Whenever I need, I can always bypass the sensor using the switch on the wall.

I can't find the sensor connection on these sensor yet, but I hope my presumption on the sensor connection is right.

See my diagram. Is my presumption correct?

OK Thanks. I need to search around. I try to avoid battery powered remote control. Many times they end up with battery lead on remote that I forget about.

I would say standard wiring in Malaysia does not have N wire pulled down to wall switch. The only place with N wire is just 3-pin wall socket. YOu should look for switch that require no N connection to avoid all these trouble.

Why would you want to remotely control since it already has remote switch. Just to control from your office?

Now you have to remote on/off and find another remote to control speed and also able to on/off.

Well, you can install one and leave it on all the time just for exquisite reason. No harm done

I have a Panasonic ceiling fan. The wall switch is always on and I control the fan solely from the remote. The problem with this stupid fan is whenever there is power trip, the fan would be default to certain mid speed when power is back on even though it was on OFF state. So, when I came back home the fan was spinning like hurricane .

Therefore, I bought a touch switch which default on OFF condition under power trip. So, remember to ask the shop and buy the fan with the behaviour you wanted.

I think this is nothing new. Switch (single or two-way), dimmer, or fan regulator with or without remote control using no hub are very common in China market. The only thing perhaps for the one using WiFi, the receiver has to be on ceiling since need more current to operate. Otherwise the standard remote control can be incorporated in switch.

The 20A double pole is not really a problem because the N is there in wall. Note the that Sonoff 20A switch is not really solution for prolonged high amp use. There are reports that the PCB get burnt. I'm not sure about the other 20A but it seems like only one manufacturer is promoting it.

You mean once the bathroom door open, the light is on? Then unless you bath with door open, you will be showering in the dark

Probably just use PIR sensor. Once detect human body heat, turn on the light depending on the bathroom brightness. Not sure why you need to have control through gateway though.

I believe that there are PIR motion detector sensor. It is much better than motion detector. It senses body heat and motion, preventing false trigger. Some has integrated time base as well. Time to go home, no time to search

No need to use door sensor switch

The PIR Motion sensor:

https://www.clipsal.com/sensors
https://shopee.com.my/TB-220V-240V-Infrared...AiABEgLGZvD_BwE

It can detect the body heat even if you shower with ice

Like I mentioned, use PIR motion sensor, i.e. it detects motion and body heat at the same time.

The motion sensor will detect motion for sure. So, so as long as there is movement, it will be kept triggered. If you have bathroom curtain, the wind might move the curtain and trigger the light. That is why I proposed PIR motion sensor. This sensor will prevent false triggering of the light. The PIR sensor uses both motion and infrared (through body heat) to trigger. This is not expensive and easy to install. You can set the ambient light, trigger when the bathroom is dark to certain level. It also has timer to delay power off in most model.

I actually do not understand why people talk about connecting the sensor to sonoff. The sensor is already smart by itself and require no intervention. What else need to be remotely controlled. You can bypass the sensor using the existing switch to bypass sensor. You just need to connect sensor in parallel to the switch. So, either sensor or wall switch can light up the light in the bathroom.

No, I do not have any motion sensor in my house. Always thinking of putting but never did. Maybe because it is not a problem to switch light on and off once enter or leave the bathroom etc. Never forget about the light either

A good one should be able to set sensitivity. You don't want to light to switch on when your cat is having shower. Cat does not need light

Wah... so poor. I guess it depends on the sensor sensitivity. Anything above 0 Kelvin emits heat energy. So, is depends on how sensitive the PIR sensor. The sensor does not radiate any signal because it is passive. ..... or perhaps ypu are cold blooded

That is why I said PIR Motion sensor, not PIR sensor. PIR motion sensor combines both IR and Motion sensors.

Good question. I never bother to find out because I think it is just like radar, which is active sensor. Now I know that that most cheap sensor uses PIR for both functions.

Here is a good article to describe how PIR is used as motion detector. So, it is said to be PIR motion detector, detect both heat and motion, for commercial reason

https://learn.adafruit.com/pir-passive-infr...r/how-pirs-work

Now I think the naming can be ambiguous. PIR Motion Sensor in general means Motion sensor that uses PIR. Therefore, it is not a sensor that is triggered by heat and movement, but just movement. That is why in your case, lack of movement switch off the light (or no triggering).

What is needed is an IR + Motion Detector . Otherwise have to dance while showering

That means you cannot close door during shower

Why not use turbine to generate electricity? When water flows out during shower, the turbine generate enough power to light up white LED light.

Yes, the PRI is not really suitable for outdoor if the background (heat) varies a lot. The object heat maybe masked by ambient temperature. Need to use active motion sensor, but need to avoid if the surround has constant movement though.