Can i use a mmWave sensor in a small bathroom?

Can I use a mmWave sensor in a small bathroom to keep lights on while someone is taking a shower behind curtains ??

Right now, I’m using a PIR motion sensor light Switch to trigger The Light To Turn On and Turn Off After Certain Periods of Time
But Sometimes you need more Time…

Could a mmWave sensor work in a small bathroom to keep the lights on while someone still occupies the bathroom? For example …To keep the lights on while someone is in the Bathtub behind a Curtain taking a shower…The PIR sensor in my light switch is constantly running out of time, turning the lights off…then the only Few choices i have are…

  1. yield the voice assistant to Turn them back on,

  2. get out of the shower and manually turn them back on…

  3. extend my arm out and wave my hand in front of the sensor to trigger the Lights to Turn Back on again …

  4. Kepp Adjusting and Changing The Time …

Or Maybe add a mmWave Sensor

I Can’t use a contact sensor cause it is a Shower curtain, not a shower door…

I Can’t use a moisture sensor cause the humidity levels take a to long to build up and takes too long to dissipate

Any Help, Advice, or Ideas will be Greatly Appreciated :pray: !

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Or another alternative? I’m not keen on a mmWave sensor due to the need for a nearby power supply.

I have a PIR sensor plus a door sensor. The PIR sensor turns the light on, but if the door remains shut, it doesn’t turn the light off. This works for me because we always leave the door open if nobody is in there (and close the door when showering :grimacing:).

The light turns off after 2 minutes if either (a) the PIR senses no motion and the door is open; or (b) the door is opened and the light is currently on. I still wait 2 minutes in case somebody is foolish enough to barge in on me and makes a hasty exit.

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A mm wave sensor would probably work. It had no trouble detecting moving trees outside my closed window :angry:


michaelblight Thank you So Much For Your Quick Reply !..

I Already Tried Combining sensors , door sensors , contact Sensors ,Humidity sensors Temperature Sensors Even added Lux " Illuminance " Sensors To The Mix…
But unfortunately didnt work …
The Mayor issue here is The Door …
Must keep the Door is open 24/7 …
Because My Cat litter Box is in the bathroom
Otherwise The Door Contact Sensor Would definitely do the trick…

I Also Understand That one of the downsides of mmWave sensors is the need of constant power…
Since they don’t work on batteries…
But thats Something i can work with …

I use one in my bathroom and it took a little to get the sensitivity and distance correct but it works great and can still see me if I am in the shower behind the wall between me and it. Right now I am using these ones.


Im using teh Aqara FP! in my main bathroom. I have glass shower doors and it will lose me when the doors fog up.


Yeah that is the 5GHz zigbee version I used. I was trying to get it to detect me in bed (micro movements) it did not work even on the highest sensitivity. I was good at detecting tree movement outside though.


Sounds like they are extremely sensitive to motion…

Rich37804 ! Really ?
I thought the wave can penetrate solid objets !

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Not sensitive enough to detect breathing under the bed covers unfortunately. Apparently you have to use the roof mounted version. Which is 240V powered and not certified for use in Australia. Inspecting one did not leave me with enough confidence to use it.

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So The wave tend to bounce back when encounters obstacles?
Or when encounters Reflections?

If the issue is people losing the light while taking a shower you might consider using an esp with an attached humidity sensor. Something like this.

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I know a lot of people take cold showers today, and in which case it might not work. But with hot showers I’d be surprised if it wouldn’t work. Seems you know when someone enters the room, so at which point you could have an automation watch for change in humidity. Minor changes would keep the light on. Just because you can’t detect the change doesn’t mean the humidity hasn’t raised enough for the sensor to detect. It should be under $15 to try it out. I think it has a good chance of working.

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Yes, a mmWave radar will work. I have the LD2410Cs with either ESP S2 Mini or ESP32 C3 Supermini in every bathroom. They see through the 9.75 mm thick glass doors on my main shower with no problem.


If you don’t want to have to solder pins on the board the M5stamp is a pretty good choice.

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bkprath Thank You For Your Reply and your Suggestions!..

Honestly i cant imagine my self taking a cold Shower in the Dark …lol…

They say it’s supposed to be good for you once you get past the initial shock.

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The Shock
:shower: :ice_cube: :cold_face: :rofl:

Had anyone Tried The New Aqara FP2 mmWave Sensor ?